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Purpose: To open up new horizons of translational research, we studied the lactate threshold (LT)–dependent physiological responses and adaptations to exercise in rats, highlighting the importance of intensity-specific studies for optimizing exercise prescriptions. LT is physiologically related to the noninvasive gas exchange threshold (GET), and both thresholds are moderate–heavy-intensity boundary indices in determining an effective intensity of aerobic training in humans. Although their practical utility is presumed to extend to rats, the actual existence of GET, the thresholds' relations to maximal oxygen consumption (V̇O2max), and whether aerobic adaptations by training differ around the LT intensity remain uncertain. Methods: This study sought to identify the GET using our previously established rat LT model by combining the use of a metabolic chamber and the V-slope method, and to confirm the thresholds' relations to V̇O2max. We investigated changes in the thresholds and V̇O2max following 6 wk of endurance training at below or above LT intensity. Results: GET and LT were significantly correlated and agreed with high precision, although with a fixed bias. Untrained rats exhibited GET and LT at 56% and 52% of their V̇O2max, respectively. Endurance training at supra-, but not below-, the LT intensity significantly improved V̇O2max and both thresholds; however, their %V̇O2max remained unaltered. Conclusions: GET in rats is identifiable as a threshold associated with LT using the V-slope method. Furthermore, both thresholds can serve as moderate–heavy-intensity boundary indices for the aerobic training of rats. This study advances our understanding of exercise intensity regulation in rats, thereby contributing to the development of a more nuanced and effective model for exercise prescription, with implications for human health and fitness. [ABSTRACT FROM AUTHOR]

Purpose: Exertional heat stress can induce systemic endotoxin exposure and a proinflammatory cascade, likely impairing thermoregulation. Cannabidiol (CBD) is protective in preclinical models of tissue ischemia and inflammation. Therefore, this study examined the effects of CBD ingestion on exercise-induced thermoregulatory and inflammatory responses. Methods: In a randomized, double-blinded study, 13 active males (age 25 ± 5 yr; peak oxygen uptake (V̇O2peak) 50.4 ± 3.2 mL·kg−1·min−1) ingested 298 mg CBD or placebo 105 min before 1 h treadmill exercise (60%–65% V̇O2peak) in 32°C and 50% relative humidity. Core temperature, skin temperature, heart rate, subjective outcomes, and sweat loss were assessed during/after exercise. Plasma osmolality, plasma volume changes, and plasma markers of intestinal damage (I-FABP), monocyte activation (CD14), and inflammatory cytokine responses (IL-6, IL-8, and TNF-α) were assessed at baseline, pre-exercise, and 20 and 90 min post-exercise. Results: Core temperature (∆ 1.69°C ± 0.48°C (CBD) and 1.79°C ± 0.53°C (Placebo)) and I-FABP increased during exercise, with no differences between conditions (P > 0.050). Mean (95% confidence interval) CD14 was 1776 (463 to 3090) pg·mL−1 greater 90 min post-exercise in placebo (P = 0.049). Median (interquartile range) peak IL-6 concentration was −0.8 (−1.1 to −0.3) pg·mL−1 less in CBD (P = 0.050), whereas the between-condition difference in IL-6 area under curve was −113 (−172 to 27) (pg·mL−1)·270 min (P = 0.054). Conclusions: CBD did not affect thermoregulation during exertional heat stress but appeared to elicit minor immunosuppressive effects, reducing CD14 and IL-6 responses, warranting investigation in humans under more severe heat strain and other proinflammatory scenarios. [ABSTRACT FROM AUTHOR]

Purpose: Burn injuries that require grafting impair thermoregulation, which may dissuade individuals with such injuries from being physically active. We tested the hypothesis that cooling modalities attenuate core temperature elevations and perceptions of heat stress during physical activity in the heat among adults with well-healed burn injuries. Methods: Adults with no burn injuries (non-burned), 20%–40% body surface area burn injuries (moderate burn), and >40% body surface area burn injuries (large burn) performed 1 h of moderate-intensity exercise (2.5 ± 0.2 mph and 2% grade) on four different occasions in two environmental conditions (30°C and 39°C, 40% relative humidity). Within each environmental condition, we applied one of the following cooling modalities, random assigned, for each visit: no cooling (control), fan at 4 m·s−1 (fan), water spray every 5 min (water spray; scaled to burn area size), or a combination of water spray + fan. Results: In 30°C, perceptual strain index (PeSI) was reduced in the non-burned and moderate burn groups with water spray + fan, whereas PeSI was reduced with all cooling modalities in the large burn group. The cooling modalities did not affect core temperature responses. In the 39°C environment, water spray and water spray + fan attenuated the elevation in core temperature (P ≤ 0.007) only in the large burn group. In the moderate burn group, PeSI was decreased with water spray + fan (P = 0.017). In the large burn group, both water spray alone and water spray + fan (P ≤ 0.041) lowered PeSI. Conclusions: For both environments across burn groups, the applied cooling modalities were generally more effective at reducing indices of perceptual strain relative to indices of thermal strain (e.g., core temperature). [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study is to investigate the effects of acute diet and exercise manipulation on resting metabolic rate (RMR) measurement variability and dual-energy x-ray absorptiometry (DXA) body composition estimates. Methods: Ten male and 10 female endurance athletes (12 cyclists, 5 triathletes, 4 runners) of tier 2 (n = 18) to tier 3 (n = 2) caliber underwent five conditions using a Latin square counterbalance design. For 24 h, athletes consumed a diet providing excessive energy availability (EA) (75 kcal⋅kg fat-free mass (FFM)−1) without exercise (GEArest), high-EA (45 kcal⋅kg FFM−1) without (HEArest) or with exercise (HEAex), or low-EA (15 kcal⋅kg FFM−1) without (LEArest) or with exercise (LEAex). Exercise involved two bouts of cycling (morning bout: 149 ± 34 min at 55% of maximal aerobic capacity (V̇O2max); afternoon bout: 60 min at 65% of V̇O2max) that resulted in a cumulative exercise energy expenditure of 30 kcal⋅kg FFM−1. The following day, RMR and DXA measurements occurred after a 10-h fast and 12-h postexercise. Results: There were neither sex differences in relative RMR (P = 0.158) nor effects of any of the five conditions on RMR (P = 0.358). For both male and female athletes, FFM estimates were decreased following the LEArest (−0.84 ± 0.66 kg; P = 0.001) and LEAex (−0.65 ± 0.86 kg; P = 0.016) conditions compared with the GEArest condition and following the LEArest (−0.73 ± 0.51 kg; P = 0.001) and LEAex (−0.54 ± 0.79 kg; P = 0.024) conditions compared with the HEAex condition. There was no effect of condition on fat mass estimates (P = 0.819). Conclusions: Acute periods of diet and exercise manipulation did not create artifacts in next-day RMR measurements. However, as changes in estimates of FFM were seen, diet and exercise should be controlled in the 24-h before DXA scans. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: The purpose of this study was to test the hypothesis that cardiovascular (CV) drift and associated decrements in maximal oxygen uptake (V̇O2max) are greater in high-fit compared with low-fit women during exercise at the same %V̇O2max, but comparable at the same rate of metabolic heat production. Methods: Six high-fit (HI) and six low-fit (LO) women cycled in 35°C for 15 or 45 min at the same relative intensity (60% V̇O2max; 15REL and 45REL) or fixed rate of heat production (500 W; 15FX and 45FX), immediately followed by a graded exercise test to measure V̇O2max. The separate 15- and 45-min trials permitted measurements of V̇O2max over the same time interval as CV drift. Results: During 45REL, higher heat production in HI (496 ± 51 vs 364 ± 44 W in LO) resulted in greater end-exercise core temperature (38.7°C ± 0.4°C vs 38.2°C ± 0.1°C, P = 0.03), greater increases in HR (15 bpm (10%) vs 10 bpm (6%), P = 0.03) and decreases in stroke volume (11 mL per beat (16%) vs 5 mL per beat (8%), P = 0.001), and larger reductions in V̇O2max (16% vs 5%, P = 0.04) compared with LO. During 45FX, temperature responses, CV drift, and decreased V̇O2max were not different between groups (all P > 0.05), despite differences in %V̇O2max (60% vs 75% for HI and LO, respectively). Conclusions: We conclude metabolic heat production modulates the CV drift–V̇O2max relationship, independent of fitness level. These results support previous findings showing the magnitude of CV drift is proportional to reductions in V̇O2max. [ABSTRACT FROM AUTHOR]

Acute ketone monoester (KE) supplementation can alter exercise responses related to endurance performance. There are limited and equivocal data regarding the effect on exercise efficiency including the influence of supplement dose. We therefore examined the effect of KE ingestion on indices of exercise efficiency during submaximal incremental cycling in trained participants. Methods: Twenty-eight adults (16 males and 12 females) aged 30 ± 10 yr (peak oxygen uptake (V̇O2peak): 59 ± 11 mL·kg−1·min−1) completed three experimental trials in a randomized, crossover, and double-blinded manner. Participants ingested either 0.3 (KE-LO) or 0.6 (KE-HI) g·kg−1 body mass of KE or a flavor-matched placebo (PLAC) ~30 min before exercise. Exercise involved a 3-min warm-up, three 5-min stages at fixed incremental workloads corresponding to 75%, 100%, and 125% of individual ventilatory threshold, followed by a ramp protocol to volitional exhaustion to determine peak power output (PPO). Results: Venous blood [ß-hydroxybutyrate], the major circulating ketone body, was higher after KE ingestion compared with PLAC (KE-HI: 3.0 ± 1.1 ≥ KE-LO: 2.3 ± 0.6 ≥ PLAC: 0.2 ± 0.1 mM; all P ≤ 0.001. There were no differences between conditions in the primary outcome exercise economy, nor gross efficiency or delta efficiency, when analyzed over the entire submaximal exercise period or by stage. Heart rate and ventilation were higher in KE-HI and KE-LO compared with PLAC when assessed over the entire submaximal exercise period and by stage (all P ≤ 0.05). PPO after the ramp was lower in KE-HI compared with both KE-LO and PLAC (329 ± 60 vs 339 ± 62 and 341 ± 61 W, respectively; both P < 0.05) despite no difference in V̇O2peak. Conclusions: KE ingestion did not change indices of exercise efficiency but increased markers of cardiorespiratory stress during submaximal incremental cycling and reduced PPO. [ABSTRACT FROM AUTHOR]

Mitochondria are essential in supplying energy to skeletal muscle. Near-infrared spectroscopy (NIRS) was developed to noninvasively assess mitochondrial capacity (mV̇O2max) as a rate constant of metabolic recovery after exercise. Purpose: This study measured the time course mV̇O2max following both maximal and submaximal exercise. Methods: Healthy male and female participants were tested (n = 12 maximal and n = 8 submaximal exercise). A NIRS device was placed on the left medial gastrocnemius. Participants performed either 1 min of maximal, rapid (~2 Hz), or submaximal (~0.37 Hz) plantar flexion exercise on a custom pneumatic ergometer. mV̇O2max was measured before and immediately after exercise. mV̇O2max measurements consisted of four incomplete recovery curves of muscle metabolism taken after 30 s of electrical muscle stimulation except in the first post-exercise to be consistent with the use of pre-exercise trial. The four recovery curves were collected 50-, 156-, 260-, and 366-s postexercise, each producing an mV̇O2max rate constant. Results: After maximal exercise, muscle acceleration decreased to 52 ± 18% (P = 0.001) of prevalues. mV̇O2max was reduced from the pre-exercise mean at the first post-trial (2.16 ± 0.44 to 1.21 ± 0.52 min−1, P < 0.001). The fourth trial showed recovery from the first (2.2 ± 0.46 min−1 vs 1.21 ± 0.52 min−1, P < 0.001) and was not significantly different from pre-exercise values (2.2 ± 0.46 vs 2.16 ± 0.44 min−1, P = 0.41). No change in acceleration or mV̇O2max was seen after submaximal exercise (P > 0.05). Conclusions: The 56.7% reduction in mV̇O2max supports the hypothesis that in young, healthy individuals, a minute of maximal exercise transiently impairs mV̇O2max, which then recovers within 6 min. The NIRS method shows promise in tracking time course changes in mV̇O2max and warrants further investigation of the transient effects of exercise on mV̇O2max. [ABSTRACT FROM AUTHOR]

Introduction: In spite of the evolving participation of transgender adults in exercise and sports, research investigating the physical fitness of transgender women remains scarce in the scientific literature. Methods: In this cross-sectional study, a variety of reference standard measures of physical fitness of transgender women who had undergone gender-affirming orchiectomy (30 ± 4 yr; n = 15) and who had not (27 ± 4 yr: n = 15) were compared with reference males (28 ± 5 yr; n = 15) and reference females (29 ± 5 yr; n = 15) who were matched for age and estimated physical activity level. Transgender women had been undergoing feminizing gender-affirming therapy for 8 to 10 yr. Results: Height and lean mass of arms, legs, and trunk (measured via dual-energy x-ray absorptiometry) of transgender women were greater than those of reference females but lower than those of reference males (all P < 0.05). No significant differences were found in isokinetic muscular torque between reference females and transgender women. Both absolute and relative measures of maximal oxygen consumption were greater in reference males than in reference females and transgender women (all P < 0.05) with no significant difference between the latter two groups. Reference males had greater peak Wingate anaerobic power (expressed in both absolute and relative to body weight), countermovement jump, and squat jump than reference females and transgender women (all P < 0.05). There were no significant differences in anaerobic power between reference females and transgender women. The results on the field tests, including agility T-test and sprint running acceleration, were consistent with the anaerobic power tests. There were no statistical differences in any of the physical fitness measures between transgender women with and without orchiectomy. Conclusions: Transgender women demonstrated similar levels of reference standard measures of physical fitness to females that were significantly lower than males. [ABSTRACT FROM AUTHOR]

Purpose: Altitude training is a common strategy used with the intent to increase hemoglobin mass (Hbmass) in athletes. However, if the Hbmass is increased during altitude camps, it seems to decline rapidly upon returning to sea level. This study aimed to examine the efficacy of three weekly heat training sessions over a 3.5-wk period after a 3-wk altitude camp on the maintenance of Hbmass in elite cyclists. Methods: Eighteen male cyclists (maximal oxygen consumption: 76 ± 5 mL·min−1·kg−1) underwent a 3-wk altitude training camp at ~2100 m above sea level. After the camp, participants were divided into one group performing three weekly heat sessions that were subtracted from their usual training (HEAT) while the other continuing usual training (CON). Training characteristics were recorded during the intervention, whereas hematological measurements were recorded before the camp as well as 2 d and 3.5 wk after the altitude camp. Results: The 3-wk altitude camp led to an overall increase in total Hbmass of 4.1%. Afterward, HEAT maintained Hbmass (0.2%, P = 0.738), whereas CON group experienced a significant reduction (−3.3%, P < 0.001) (ΔHEAT vs ΔCON, P < 0.001). Moreover, HEAT increased plasma volume (PV) by 11.6% (P = 0.007) and blood volume (BV) by 5.8% (P = 0.007), whereas CON only showed an increase in PV (5.5%, P = 0.041). Exercise intensity and training load were not different between groups during the maintenance period. Conclusions: This study suggests that incorporating three weekly heat training sessions into the usual training routine preserves a moderately increased Hbmass in elite cyclists after an altitude camp. [ABSTRACT FROM AUTHOR]

Purpose: Vigorous intermittent lifestyle physical activity (VILPA) are bursts of incidental vigorous activity that occur during day-to-day activities outside of the exercise-domain. Vigorous intermittent lifestyle physical activity has shown promise in lowering risk of mortality and chronic disease. However, there is an absence of an empirically derived definition. Using physiological and effort-based metrics commonly used to define vigorous intensity, we investigated the minimum time needed to elicit physiological and perceived exertion responses to standardized activities of daily living. Methods: Seventy adults (age = 58.0 ± 9.6 yr; 35 female) completed 9 VILPA activities of daily living in a randomized order, which included fast walking, fast incline walking, stair climbing, stationary cycling, and carrying external weight equal to 5% and 10% of body weight. Metabolic rate (by continuous indirect calorimetry), heart rate (telemetry) and perceived effort (Borg Scale) were measured during exercise. Time to reach VILPA was assessed using %V̇O2max, %HRmax, and rating of perceived exertion thresholds. Results: The mean time to elicit VILPA ranged from 65 to 95 s (mean ± sd = 76.7 ± 3.8 s) for %V̇O2max, 68 to 105 s (mean ± sd = 82.8 ± 6.8 s) for %HRmax, and 20 to 60 s (mean ± sd = 44.6 ± 6.7 s) for rating of perceived exertion. For each of the three indices, there was no difference in the time to elicit VILPA responses by sex or age (P > 0.08), and times were also consistent between activities of daily living tasks. For example, for females and males, the average time to elicit vigorous responses while walking on a flat surface was 85.8 s (±16.9 s) and 80 s (±13.9 s), respectively, and for stair climbing while carrying 10% of body weight the duration was 78.4 s (±17.6 s) and 76.9 (±17.7 s). Conclusions: When participants undertook activities of daily living, VILPA elicited a physiological response at an average of 77 to 83 s for %V̇O2max and %HRmax, and 45 s for perceived exertion. The absence of a difference in the time to reach VILPA between sex and age suggests that a consistent behavioral VILPA translation can be used in interventions and population-based studies designed to assess the health effects of incidental physical activity. [ABSTRACT FROM AUTHOR]

Purpose: Given the rising burden of heart failure (HF), stratification of patients at increased risk for adverse events is critical. We aimed to compare the predictive value of various maximal and submaximal cardiopulmonary exercise test (CPET) variables for adverse events in patients with HF. Methods: A total of 237 patients with HF (66 (58–73) yr, 30% women, 70% HF with reduced ejection fraction) completed a CPET and had 5 yr of follow-up. Baseline characteristics and clinical outcomes (all-cause mortality, major adverse cardiovascular events, and cardiovascular-related hospitalization) were extracted from electronic patient files. Receiver operating characteristics curves for maximal (e.g., peak V̇O2) and submaximal CPET variables (e.g., VE/V̇CO2 slope, cardiorespiratory optimal point (COP), V̇O2 at anaerobic threshold) were compared using the Akaike Information Criterion (AIC) method, whereas their calibration was assessed. Results: One hundred three participants (43%) reached the composite endpoint, and 55 (23%) died. Percent predicted peak V̇O2 was the best predictor for adverse outcomes (AIC: 302.6) followed by COP (AIC: 304.3) and relative peak V̇O2 (mL·(kg·min)−1, AIC: 304.4). Relative peak V̇O2 (AIC: 217.1) and COP (AIC: 224.4) were also among the three best predictors for mortality, together with absolute peak V̇O2 (mL·min−1, AIC: 220.5). A good calibration between observed and predicted event rate was observed for these variables. Conclusions: Percent predicated and relative peak V̇O2 had the best predictive accuracy for adverse events and mortality, but the submaximal COP had a noninferior predictive accuracy for adverse events in patients with HF. These findings highlight the potential of submaximal exercise testing in patients with HF. [ABSTRACT FROM AUTHOR]

Purpose: Body cooling during and after exercise stimulates energy intake (EI). Cooling vests can also reasonably decrease body temperature under various sport occasions. This study examined the acute effects of wearing a cooling vest on EI and appetite after exercise and rest. Methods: Fifteen healthy young men underwent four trials randomly in a thermoneutral room (~24°C, ~40% humidity). In two exercise trials, participants performed a 60-min run at 75% of maximum oxygen uptake and wore a cooling vest (ExC) or thermoneutral vest (ExN) from 1030 to 1130 h. In two resting trials, participants rested for 60 min and wore a cooling vest (RC) or a thermoneutral vest (RN) from 1030 to 1130 h. From 1130 h, participants consumed a buffet meal until satiety. EI was calculated from the buffet meal. Skin and rectal temperatures were assessed between 0930 and 1130 h. Results: EI was significantly higher in the ExC trial (1740 ± 642 kcal) than in the ExN trial (1584 ± 604 kcal) and higher in the RC trial (1879 ± 806 kcal) than in the RN trial (1726 ± 806 kcal). Hot food consumption was significantly higher in the ExC trial than in the ExN trial and higher in the RC trial than in the RN trial. Subjective hunger was significantly higher in the ExC trial than in the ExN trial. Lower rectal temperatures were associated with higher relative EI (β = −8.871, P < 0.001). Conclusions: Wearing a cooling vest increased EI after exercise or rest and increased subjective appetite only after exercise. Increased EI may result from a preference for hot foods altered by a cooling vest. [ABSTRACT FROM AUTHOR]

Introduction: Running economy (RE) deteriorates during prolonged running, although the effect of measuring energy cost (EC) or oxygen cost (OC) on the magnitude of these changes has not been investigated. Similarly, it is unknown if runners’ performance level may influence the deterioration of RE during prolonged running. The aims of this study were to compare changes in EC and OC measurements of RE during a prolonged run in a large cohort of well-trained male runners, and to compare changes between runners of high- and low-performance standard. Methods: Forty-four male runners (maximal oxygen uptake (V̇O2max) 62.4 mL·kg-1 ·min-1 ; 10-km time: 35:50 ± 4:40 mm:ss) completed an incremental test determining lactate threshold 1 (LT1) and V̇O2max, and on a separate occasion, a 90-min run at LT1. Respiratory gases were collected at 15-min intervals. Subsequently, subgroups of high- (HP; 10-km time: 31:20 ± 01:00 mm:ss) and low-performing (LP; 10-km time: 41:50 ± 01:20 mm:ss) runners were compared. Results: RE deterioration was only fractionally larger when expressed as OC than EC (0.1% greater from 30-90 min; P < 0.001), perhaps due to the small change in respiratory exchange ratio (-0.01) in this study. For the HP group, increases were lower than LP after 90 min in both EC (+2.3% vs +4.3%; P < 0.01) and OC (+2.4% vs +4.5%; P < 0.01). Similarly, at standardized distances, changes were lower for HP versus LP, for example, at 16.7 km + 1.0 versus +3.2% for EC (P < 0.01), and +1.2 vs +3.4% for OC (P < 0.001). Conclusions: The deterioration of RE was dependent on athlete’s performance level, with HP runners displaying superior RE durability. The use of EC or OC had only a fractional influence on RE durability, although this may gain importance with larger shifts in substrate metabolism. [ABSTRACT FROM AUTHOR]

Purpose: This study reports the results of a 20-yr (2005 to 2024) follow-up study of two 2-time Olympic and 6-time world champion rowing athletes. To provide a comprehensive picture of adaptations in physiological and performance characteristics to long-term training, we monitored the athletes’ physiological and performance data annually through five 4-yr developmental phases. Methods: Maximal oxygen uptake ( V̇O2max), maximal minute power (MMP), and power output corresponding to anaerobic threshold (PAT) were derived from a rampwise exercise test on a rowing ergometer. In addition, average power output sustained during all-out tests over 2000 and 6000 m on a rowing ergometer was also obtained. Results: V̇O2max peaked at age 22 for athlete A and at age 25 for athlete B (at ~7 L·min-1 ) before stabilizing and then gradually declining to a range of 6.2 to 6.5 L·min-1 for both athletes. MMP stabilized in both rowers at values between 550 and 575 W and displayed minimal fluctuations over the final two phases of the study. In addition, MMP closely resembled the corresponding average power output sustained during the 2000-m all-out tests on a rowing ergometer. Average power output during 2000 and 6000-m all-out tests showed steady improvements over the monitored phases of the study, with the highest power output crew averages for both 2000-m (532 W; 5 min 48 s) and 6000-m (463 W; 18 min 4 s) tests recorded during the last 4-yr phase of the assessment. Conclusions: Improvements in rowing ergometer performance over 2000 and 6000 m appear to be largely independent of the multiyear changes in V̇O2max. Long-term rowing training resulted in continuous improvements in MMP and PAT throughout the monitored phases, which more closely mimicked improvements in rowing ergometer performance. [ABSTRACT FROM AUTHOR]

Purpose: Platelets are key mediators in cardiovascular disease (CVD). Low cardiorespiratory fitness (CRF) is a risk factor for CVD. The purpose of our study was to assess if CRF associates with platelet function. Methods: Platelet assays and cardiopulmonary exercise testing were conducted in the Framingham Heart Study (N = 3014). Linear mixed effects models estimated associations between CRF (assessed by peak oxygen uptake [V̇O2]) and multiple platelet reactivity assays. Models were adjusted for multiple medications, risk factors, relatedness, and prevalent CVD. Results: Nineteen associations passed the significance threshold in the fully adjusted models, all indicating higher CRF associated with decreased platelet reactivity. Significant traits spanned multiple platelet agonists. Strongest associations were observed in multiplate whole blood testing after TRAP-6 (e.g., velocity, beta = -0.563, 95% CI = -0.735 to -0.391, P = 1.38E-10), ADP (e.g., velocity, beta = -0.514, 95% CI = -0.681 to -0348, P = 1.41E-09), collagen (e.g., velocity, beta = -0.387, 95% CI = -0.549 to -0.224, P = 3.01E-06), ristocetin (e.g., AUC, beta = -0.365, 95% CI = -0.522 to -0.208, P = 5.17E-06) and arachidonic acid stimulation of platelets (e.g., velocity, beta = -0.298, 95% CI = -0.435 to -0.162, P = 3.39E-04), and light transmission aggregometry (LTA) after ristocetin stimulation (e.g., max aggregation, beta = -0.362, 95% CI = -0.540 to -0.184, P = 6.64E-05). One trait passed significance threshold in the aspirin subsample (LTA ristocetin primary slope, beta = -0.733, 95% CI = -1.134 to -0.333, P = 3.30E-04) and another in a model including von Willebrand Factor levels as a covariate (U46619, a thromboxane receptor mimetic, AUC in the Optimul assay, beta = -0.36, 95% CI = -0.551 to -0.168, P = 2.35E-04). No strong interactions were observed between the associations and sex, age, or body mass index in formal interaction analyses. Conclusions: Our findings build on past work that shows CRF to be associated with reduced CVD by suggesting decreased platelet reactivity may play a mechanistic role. We found significant associations with multiple platelet agonists, indicating higher CRF may globally inhibit platelets; however, given multiple strong associations after TRAP-6 and ADP stimulation, PAR-1 and purinergic signaling may be most heavily involved. This is notable because each of these receptor pathways are tied to anticoagulant (DOAC/thrombin inhibitors) and antiplatelet therapies (P2Y12/PAR1/PAR4 inhibitors) for CVD prevention. [ABSTRACT FROM AUTHOR]

Aquatic high-intensity interval training deep water running (AHIIT-DWR) has the potential to improve cardiometabolic health and cognitive psychological responses, offering a reduced risk of injuries and greater affordability for inactive elderly women. Purpose: To investigate the effects of an 8-wk AHIIT-DWR intervention compared with land-based HIT training (LHIIT) on cardiometabolic health, cognitive, and psychological outcomes in inactive elderly women. Methods: Seventy inactive elderly women aged 60 yr or above were randomly assigned into two groups: AHIIT-DWR and LHIIT. The AHIIT-DWR group engaged in DWR sessions comprising 30 min of interval training, consisting of ten 2-min exercise bouts at 80%-90% of their maximal heart rate (HRmax), with 1-min active recovery at 70% HRmax between bouts, for two sessions per week, for 8 wk. The LHIIT group performed treadmill running at the same intensity. Results: Both groups showed similar cardiovascular fitness, maximal aerobic capacity (VO2max), HRmax, and RER improvement (P > 0.05), whereas AHIIT-DWR showed a significant improvement in aerobic capacity minute ventilation (VE), metabolic equivalents (METs), and O2 pulse (P < 0.05) over the 8-wk intervention. Both AHIIT-DWRand LHIIT significantly decreased triglycerides, total cholesterol, HDL, and LDL postintervention (P < 0.05). No significant group differences were observed for cognitive function assessed by MMSE and MOCA (P > 0.05). Both groups showed similar enjoyment levels, self-efficacy scores, and high adherence rates (>90%). Conclusions: Our study suggests that AHIIT-DWR can elicit a similar improvement in cardiorespiratory health, metabolic bloodmarkers, cognitive function assessed byMMSE andMOCA, and psychological responses as LHIIT in inactive elderly women. [ABSTRACT FROM AUTHOR]

Impact of Eccentric versus Concentric CyclingExercise onNeuromuscular Fatigue andMuscleDamage inBreastCancerPatients. Med. Sci. Sports Exerc., Vol. 56, No. 11, pp. 2103-2116, 2024. Introduction: This study investigated the magnitude and etiology of neuromuscular fatigue and muscle damage induced by eccentric cycling compared with conventional concentric cycling in patients with breast cancer. Methods: After a gradual familiarization protocol for eccentric cycling, nine patients with early-stage breast cancer performed three cycling sessions in eccentric or concentric mode. The eccentric cycling session (ECC) was compared with concentric cycling sessions matched for power output (CONpower; 80% of concentric peak power output, 95 ± 23W) or oxygen uptake (CONV_ O2; 10 ± 2 mL·min·kg-1). Preexercise to postexercise changes (30-s through 10-min recovery) in knee extensor maximal voluntary contraction force (MVC), voluntary activation, and quadriceps potentiated twitch force (Qtw) were quantified to determine global, central, and peripheral fatigue, respectively. Creatine kinase and lactate dehydrogenase activities were measured in the plasma before and 24 h after exercise as markers of muscle damage. Results: Compared with CONpower (-11% ± 9%) and CONV_ O2 (-5% ± 5%), the ECC session resulted in a greater decrease inMVC (-25% ± 12%) postexercise (P < 0.001). Voluntary activation decreased only in ECC (-9% ± 6% postexercise, P < 0.001). The decrease in Qtw was similar postexercise between ECC and CONpower (-39% ± 21% and -40%± 16%, P > 0.99) but lower in CONV_ O2 (P < 0.001). The CONpower session resulted in twofold greaterV_ O2 compared with the ECC and CONV_ O2 sessions (P < 0.001). No change in creatine kinase or lactate dehydrogenase activity was reported from preexercise to 24 h postexercise. Conclusions: The ECC session induced greater neuromuscular fatigue compared with the concentric cycling sessions without generating severe muscle damage. ECC is a promising exercise modality for counteracting neuromuscular maladaptation in patients with breast cancer. [ABSTRACT FROM AUTHOR]

Purpose: We studied the effect of O2 supplementation on physiological response to exercise in patients with moderate to severe interstitial lung disease (ILD). Methods: Thirteen patients (age 66 ± 10 yr, 7 males) with ILD (total lung capacity, 71% ± 22% predicted; carbon monoxide diffusion capacity, 44%± 16%predicted) and 13 healthy individuals (age 50 ± 17 yr, 7 males) were tested. ILD patients performed symptom-limited cardiopulmonary exercise tests and constant work rate (WR) tests at 80% of the WR at the gas exchange threshold. Tests breathing room air (RA; 21% O2) were compared with tests performed breathing 30% O2. Oxygen uptake (VO2) kinetics were calculated from the constantWRtest results. Results: In the ILDgroup, peakWR, peakVO2, andVO2 at the gas exchange threshold improved significantlywhen breathing 30% O2 compared with RA (mean ± SD, 75 ± 26 vs 66 ± 23 W, 17 ± 4 vs 15 ± 2 mL·kg-1·min-1, and 932 ± 245 vs 854 ± 232 mL·min-1; P = 0.004, P = 0.001, and P = 0.01, respectively). O2 saturation (SpO2%) at peak exercise was higher with 30% O2 (97% ± 4% vs 88% ± 9%, P = 0.002). The time constant (tau) of VO2 kinetics was faster in ILD patients while breathing 30% O2 (41 ± 10 s) compared with RA (52 ± 14 s, P = 0.003). There was a negative linear relation between tau and SpO2% with RA (r = -0.76, P = 0.006) and while breathing 30%O2 (r = -0.68, P = 0.02). Conclusions: Using a clinically applicable level of O2 supplementation (30%) improvedmaximal, aerobic exercise capacity and VO2 kinetics in ILD patients, likely due to increased blood O2 content subsequently increasing the O2 delivery to the working muscles. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to compare the physiological adaptations of males and females to repeated sprint training in hypoxia (RSH). Methods: Active males and females completed 7 wk of repeated sprint training in normoxia (RSN; Fi O2 = 0.209, males: n = 11, females: n = 8) or RSH (Fi O2 = 0.146, males: n = 12, females: n = 10). Before (Pre-) and after (Post-) training, a repeated sprint ability (RSA) test was performed (10-s cycle sprints with 20-s recovery between sprints, until exhaustion), and aerobic and anaerobic qualities were evaluated in normoxia. Results: The number of sprints during RSA increased after training in HYP from 11 to 21 in males and from 8 to 14 in females (P < 0.001, 95% confidence interval = 5–11), without significant changes after RSN (10 vs 14 and 8 vs 10 in males and females, respectively). No improvements in mean or peak power output were found in either group. Total work during RSA improved after training in all groups (+9 ± 2 kJ, P < 0.001). Tissue saturation index during the repeated sprints was higher in females than males (+10% ± 2%, P < 0.001). The difference in tissue saturation index between the recovery and sprint phases remained unchanged after training. V̇O2peak during an incremental exercise test increased in all groups (+3 ± 1 mL·kg−1 ·min−1 , P = 0.039). Mean power output during a Wingate test also increased in both males and females in RSN and RSH (+0.38 ± 0.18 W·kg−1 , P = 0.036). No changes were observed in hematological parameters after training. Conclusions: Seven weeks of RSH further increased the number of repeated sprints performed to exhaustion compared with RSN in females, in the same order of magnitude as in males. [ABSTRACT FROM AUTHOR]

Introduction: The effect of eccentric exercise--induced muscle damage (EIMD) on cycling efficiency is unknown. The aim of the present study was to assess the effect of EIMD on gross and delta efficiency and the cardiopulmonary responses to cycle ergometry. Methods: Twenty-one recreational athletes performed cycling at 70%, 90%, and 110% of the gas exchange threshold (GET) under control conditions (Control) and 24 h following an eccentric damaging protocol (Damage). Knee extensor isometric maximal voluntary contraction, potentiated twitch (Qtw,pot), and voluntary activation were assessed before Control and Damage. Gross and delta efficiency were assessed using indirect calorimetry, and cardiopulmonary responses were measured at each power output. Electromyography root-mean-square (EMGRMS) during cycling was also determined. Results: Maximal voluntary contraction was 25%± 18%lower for Damage than Control (P < 0.001). Gross efficiency was lower for Damage than Control (P < 0.001) by 0.55% ± 0.79%, 0.59% ± 0.73%, and 0.60% ± 0.87% for 70%, 90%, and 110% GET, respectively. Delta efficiency was unchanged between conditions (P = 0.513). Concurrently, cycling EMGRMS was higher for Damage than Control (P = 0.004). An intensity-dependent increase in breath frequency and ... was found, which were higher for Damage only at 110% GET (P ≤ 0.019). Conclusions: Thus, gross efficiency is reduced following EIMD. The concurrently higher EMGRMS suggests that increases in muscle activation in the presence of EIMD might have contributed to reduced gross efficiency. The lack of change in delta efficiency might relate to its poor reliability hindering the ability to detect change. The findings also show that EIMD-associated hyperventilation is dependent on exercise intensity, which might relate to increases in central command with EIMD. [ABSTRACT FROM AUTHOR]

Purpose: We investigated the effects of low- and high-volume speed endurance training (SET), with a reduced training volume, on sprint ability, short- and long-term exercise capacity, muscle mitochondrial properties, ion transport proteins, and maximal enzyme activity in highly trained athletes. Methods: Highly trained male cyclists (maximal oxygen consumption (...): 68.3 ± 5.0 mL⋅min-1⋅kg-1, n = 24) completed 6 wk of either low (SET-L; 6 x 30-s intervals, n = 8) or high (SET-H; 12 x 30-s intervals, n = 8) volume SET twice per week with a 30% reduction in training volume. A control group (CON; n = 8) maintained their training. Exercise performance was evaluated by i) 6-s sprinting, ii) a 4-min time trial, and iii) a 60-min preload at 60% ... followed by a 20-min time trial. A biopsy of m. vastus lateralis was collected before and after the training intervention. Results: In SET-L, 4-min time trial performance was improved (P < 0.05) by 3.8%, with no change in SET-H and CON. Sprint ability, prolonged endurance exercise capacity, ..., muscle mitochondrial respiratory capacity, maximal citrate synthase activity, fiber type--specific mitochondrial proteins (complexes I-V), and phosphofructokinase (PFK) content did not change in any of the groups. In SET-H, maximal activity of muscle PFK and abundance of Na+-K+ pump-subunit α1, α2, β1, and phospholemman (FXYD1) were 20%, 50%, 19%, 24%, and 42% higher (P < 0.05), respectively after compared with before the intervention, with no changes in SET-L or CON. Conclusions: Low SET volume combined with a reduced aerobic low- and moderate-intensity training volume does improve short-duration intense exercise performance and maintain sprinting ability, ..., endurance exercise performance, and muscle oxidative capacity, whereas, high volume of SET seems necessary to upregulate muscle ion transporter content and maximal PFK activity in highly trained cyclists. [ABSTRACT FROM AUTHOR]

Introduction: Chronic fatigue is the most common and debilitating symptomin people with multiple sclerosis (PwMS). Recently, exercise has been proven to alleviate chronic fatigue and improve physical functions. Tailoring the training intervention to the potential fatigue causes could optimize the beneficial effects of training on fatigue. The objective of this study was to compare the effectiveness of an individualized (IND) versus a traditional (TRAD) exercise intervention in reducing chronic fatigue. Methods: Twenty-nine PwMS with high chronic fatigue were randomly assigned to 12 wk of either a TRAD or IND exercise intervention. TRAD comprised aerobic and resistance exercises according to the guidelines for PwMS. IND specifically addressed identified individual weaknesses. Participants visited the laboratory before and after training for the following assessments: patient-reported outcomes (fatigue, quality of life, depression questionnaires), incremental cycling test (peak oxygen uptake (...)), and cycling fatigue test (maximal voluntary contraction, rating of perceived exertion). Results: Similar improvements in fatigue, depression, and quality of life were observed between groups (P > 0.05). Compared with TRAD, IND induced a significant greater increase in ... (+21.0% ± 13.9% vs 6.8%± 11.5%, P < 0.05) and a greater reduction in rating of perceived exertion at a given submaximal intensity (-30.3% ± 18.9% vs -12.1% ± 20.4%, P < 0.001), whereas maximal voluntary contraction increased similarly in both groups (P > 0.05). Conclusions: Although tailored exercise improved similarly fatigue and other subjective parameters (depression, quality of life, sleep quality) compared with than traditional exercise intervention, prescribing an individualized intervention led to greater improvement in ... (but not maximal strength) and perception of effort. This may have positive functional consequences for patients. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the effect of the MC and endogenous sex hormone concentrations on performance-determining variables in three distinctMC phases in endurance-trained females. Methods: Twenty-one eumenorrheic trained/highly trained endurance athletes completed a standardized test battery during the early follicular phase (EFP), ovulatory phase (OP), and midluteal phase (MLP) for either one (n = 7) or two test cycles (n = 14). MC phases were determined using calendar-based counting, urinary ovulation testing, and verified with serum hormone analysis. MCs were retrospectively classified as eumenorrheic or disturbed. Disturbed MCs were excluded from analysis. The test battery consisted of 4-6 x 5-min submaximal stages with stepwise speed increases, a 30-s all-out double-poling ski ergometer test, and a maximal incremental treadmill running test. Results: At a group level, there was no effect of MC phase or the serum concentrations of estrogen and progesterone on peak oxygen uptake (...), oxygen uptake at 4 mmol⋅L-1 blood lactate concentration, time to exhaustion, running economy, or mean 30-s power output (MPO30s). Serum testosterone concentration was positively associated with MPO30s (P = 0.016). Changes in ... from EFP to MLP were inconsistent between individuals and across cycles. Conclusions: None of the measured performance-determining variables were influenced by MC phase or serumestrogen or progesterone concentrations. Although some individual patterns could be observed, there was no indication that any single MC phase is consistently associated with improved or impaired ... on a group level. [ABSTRACT FROM AUTHOR]

Purpose: Cardiorespiratory fitness (CRF) measured by peak oxygen consumption (...) declines with aging and correlates with mortality and morbidity. Cardiopulmonary exercise testing (CPET) is the criterion method to assess CRF, but its feasibility, validity, and reliability in older adults are unclear. Our objective was to design and implement a dependable, safe, and reliable CPET protocol in older adults. Methods: ... was measured by CPET, performed using treadmill exercise in 875 adults ≥70 yr in the Study of Muscle, Mobility and Aging (SOMMA). The protocol included a symptom-limited peak (maximal) exercise and two submaximal walking speeds. An adjudication process was in place to review tests for validity if they met any prespecified criteria (... <12.0 mL⋅kg-1⋅min-1; maximum heart rate <100 bpm; respiratory exchange ratio <1.05 and a rating of perceived exertion <15). A subset (N = 30) performed a repeat test to assess reproducibility. Results: CPET was safe and well tolerated, with 95.8% of participants able to complete the // phase of the protocol. Only 56 (6.4%) participants had a risk alert and only two adverse events occurred: a fall and atrial fibrillation. Mean ± SD ... was 20.2 ± 4.8 mL⋅kg-1⋅min-1, peak heart rate 142 ± 18 bpm, and peak respiratory exchange ratio 1.14 ± 0.09. Adjudication was indicated in 47 tests; 20 were evaluated as valid and 27 as invalid (18 data collection errors, 9 did not reach ...). Reproducibility of ... was high (intraclass correlation coefficient = 0.97). Conclusions: CPET was feasible, effective, and safe for older adults, including many with multimorbidity or frailty. These data support a broader implementation of CPET to provide insight into the role of CRF and its underlying determinants of aging and age-related conditions. [ABSTRACT FROM AUTHOR]

Introduction: Low cardiorespiratory fitness (CRF) increases the risk of cardiovascular disease by up to eightfold and is one of the strongest predictors of mortality. Some studies demonstrate impaired CRF in people living with type 1 and type 2 diabetes compared with those without diabetes, whereas others demonstrate no diabetes-associated impairment in CRF. Purpose: We aimed to determine whether diabetes can influence CRF and, if so, identify clinical associations underlying diabetes-associated exercise impairments. Methods: Sixty-eight studies were included in the quantitative analysis. Standardized mean difference (SMD) was calculated and meta-analyses and meta-regressions were performed by using a random-effects model. Results: Diabetes is associated with a large negative effect on CRF (SMD = -0.80, P < 0.001)--an effect that is partially mitigated, but still significant, in those with high physical activity levels (SMD = -0.50, P = 0.007). A sedentary lifestyle (SMD = -0.83, P = 0.007) and the presence of clinical complications related to diabetes (SMD = -1.66, P < 0.001) predict a greater magnitude of CRF reduction in people with diabetes compared with controls without diabetes. Both type 1 diabetes and type 2 diabetes are independently associated with impaired CRF compared with controls without diabetes; however, the effect is significantly greater in those type 2 diabetes (SMD = -0.97, P < 0.001).Meta-regression analysis demonstrates the effects of diabetes on CRF are primarily associated with HbA1c levels for type 1 diabetes (B = -0.07, P < 0.001) and body mass index for type 2 diabetes (B = -0.17, P = 0.005). Conclusions: These data demonstrate a negative influence of diabetes on the key risk factor of low CRF and provide critical insight into specific clinical markers of low CRF associated with diabetes. [ABSTRACT FROM AUTHOR]

IntroductionSeveral studies report that pulmonary oxygen uptake (V̇O 2 ) at the respiratory compensation point (RCP) is equivalent to the V̇O 2 at critical power (CP), suggesting that the variables can be used interchangeably to demarcate the threshold between heavy and severe intensity domains. However, if RCP is a valid surrogate for CP, their values should correspond even when assessed in patients with chronic obstructive pulmonary disease (COPD) in whom the "normal" mechanisms linking CP and RCP are impeded. The aim of this study was to compare V̇O 2 at CP with V̇O 2 at RCP in patients with COPD.MethodsTwenty-two COPD patients (14 male/8 female; forced expiratory volume in 1 s, 46% ± 17% pred) performed ramp-incremental cycle ergometry to intolerance (5-10 W·min -1 ) for the determination of gas exchange threshold (GET) and RCP. CP was calculated from the asymptote of the hyperbolic power-duration relationship from 3-5 constant-power exercise tests to intolerance. CP was validated with a 20-min constant-power ride.ResultsGET was identified in 20 of 22 patients at a V̇O 2 of 0.93 ± 0.18 L·min -1 (75% ± 13% V̇O 2peak ), whereas RCP was identified in just 3 of 22 patients at a V̇O 2 of 1.40 ± 0.39 L·min -1 (85% ± 2% V̇O 2peak ). All patients completed constant-power trials with no difference in peak physiological responses relative to ramp-incremental exercise ( P > 0.05). CP was 46 ± 22 W, which elicited a V̇O 2 of 1.04 ± 0.29 L·min -1 (90% ± 9% V̇O 2peak ) during the validation ride. The difference in V̇O 2 at 15 and 20 min of the validation ride was 0.00 ± 0.04 L, which was not different from a hypothesized mean of 0 ( P = 0.856), thereby indicating a V̇O 2 steady state.ConclusionsIn COPD patients, who present with cardiopulmonary and/or respiratory-mechanical dysfunction, CP can be determined in the absence of RCP. Accordingly, CP and RCP are not equivalent in this group.

The article investigates how capillary red cell transit time significantly impacts exercise-induced pulmonary diffusion limitation, with increased pulmonary artery pressure and cardiac output contributing to decreased transit times. It also discusses the effects of ventilation–perfusion mismatch, changes in diffusing capacity (DL), and the role of increased cardiac output in impairing oxygen diffusion equilibrium during intense exercise.

Introduction: Contrary to common belief, a growing body of evidence suggests that unsatisfied inspiration (UI), an inherently uncomfortable quality of dyspnea, is experienced by ostensibly healthy adults during highintensity exercise. Based on our understanding of the mechanisms of UI among people with chronic respiratory conditions, this analysis tested the hypothesis that the experience of UI at peak exercise in young, healthy adults reflects the combination of high ventilatory demand and critical inspiratory constraints. Methods: In a retrospective analysis design, data included 321 healthy individuals (129 females) aged 25 ± 5 yr. Data were collected during one visit to the laboratory, which included anthropometrics, spirometry, and an incremental cardiopulmonary cycling test to exhaustion. Metabolic and cardiorespiratory variables were measured at peak exercise, and qualitative descriptors of dyspnea at peak exercise were assessed using a list of 15 descriptor phrases. Results: Thirty-four percent of participants (n = 109) reported sensations of UI at peak exercise. Compared with the non-UI group, the UI group achieved a significantly higher peak work rate (243 ± 77 vs 235 ± 69 W, P = 0.016, d = 0.10), rate of O2 consumption (3.32 ± 1.02 vs 3.27 ± 0.96 L·min-1, P = 0.018, d = 0.05), minute ventilation (120 ± 38 vs 116 ± 35L·min-1, P = 0.047, d = 0.11), and breathing frequency (50 ± 9 vs 47 ± 9 breaths per minute, P = 0.014, d = 0.33), while having a lower exercise-induced change (peak-baseline) in inspiratory capacity (0.07 ± 0.41 vs 0.20 ± 0.49 L, P = 0.023, d = 0.29). The inspiratory reserve volume to minute ventilation ratio at peak exercise was also lower in the UI versus non-UI group. Dyspnea intensity and unpleasantness ratings were significantly higher in the UI versus non-UI group at peak exercise (both P < 0.001). Conclusions: Healthy individuals reporting UI at peak exercise have relatively greater inspiratory constraints compared with those who do not select UI. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the effects of a 7-d high-intensity interval training shock microcycle (HIIT-SM) with or without additional low-intensity training (LIT) on aerobic fitness and endurance performance compared with a control group (CG). Methods: Thirty-three endurance-trained athletes (7 women, 26 men, mean ± SD: age, 30.2 ± 6.9 yr;maximal oxygen uptake (VO2max), 59.8 ± 4.9 mL·min-1·kg-1) performed exercise testing at T1 and were randomly assigned to one of three groups: i) HSM, 10 running-based HIIT sessions (5 × 4 min at 90%-95% maximal heart rate) over 7 d; ii)HSM+ LIT, equal toHSMwith additional 30 min of LIT after each HIIT; iii) CG, regular training. Exercise testing was repeated 3 d (T2), 7 d (T3), and 14 d (T4) after the intervention. A 5-km time trial (TT5km) was performed 3-4 d before T1 and 10-11 d after the intervention. Data were analyzed by two-way repeated-measures ANOVA. Results: No interaction effect was found for VO2max (P = 0.170, pη² = 0.09), peak power output (P = 0.734, pη² = 0.04), and work economy (P = 0.804, pη² = 0.03). There was an interaction for velocity at lactate threshold (P = 0.006, pη² = 0.18) with increased velocity in HSM at T2 (3.2%, P = 0.030), T3 (4%, P = 0.006), T4 (4%, P = 0.003), as well as in HSM + LIT for T2 (3.2%, P = 0.011), whereas CG showed no change. There was an interaction for TT5km (P = 0.044, pη² = 0.19), with HSM improving 2.7% (P = 0.003) and HSM + LIT 2.3% (P = 0.010), whereas CG was, on average, -0.3% (P = 0.821) slower. Conclusions: HIIT-SM with or without additional LIT has negligible effects on VO2max but improves other key endurance variables in endurance-trained athletes. No superiority of either intervention group was demonstrated. Therefore, additional LIT during HIIT-SM is not beneficial. [ABSTRACT FROM AUTHOR]

Purpose: Bothmaximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach itsmaximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations duringmaximalintensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia. Methods: Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit. Results: EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different (P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio (P = 0.029), higher ventilation (VE) (P < 0.001), larger ΔVO2max (P = 0.019), and lower hypoxia-relatedV E increase (P < 0.001). Conclusions: Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to determine associations between running economy (RE) and running sagittal plane kinematic and kinetic parameters. Method: A total of 30 male recreational runners (age: 21.21 ± 1.22 yr, VO2max: 54.61 ± 5.42 mL·kg-1·min-1) participated in two separate test sessions. In the first session, the participant's body composition and RE at 10 and 12 km·h-1 were measured. In the second session, measurements were taken for the sagittal plane of hip, knee, and ankle angles and range of motion (ROM), as well as ground reaction force. Results:Moderate correlations were found between lower energy costs at 12 km·h-1 and smaller hip flexion at toe-off (r = 0.373) as well as smaller peak hip flexion during stance (r = 0.397). During the swing phase, lower energy costs at 10 km·h-1 were moderately correlated with smaller peak knee flexion and smaller knee flexion and extension ROM (r = 0.366-0.443). Lower energy costs at 12 km·h-1 were moderately correlated with smaller peak hip and knee flexion as well as knee extension ROM(r = 0.369-0.427). In terms of kinetics, there was a moderate correlation between higher energy costs at 10 km·h-1 and larger peak active force, as well as larger peak braking and propulsion force (r = -0.470-0.488). Lower energy costs at 12 km·h-1 were moderately to largely correlated with smaller peak impact and braking force (r = 0.486 and -0.500, respectively). Regarding the statistical parametric mapping analysis, most outcomes showed associations with RE at 10 km·h-1, including knee flexion (42.5%-65.5%of the gait cycle), ankle plantarflexion (32.5%-36%of the gait cycle), active force (30.5%-35%of the stance phase), and propulsion force (68%-72.5% of the stance phase). Lower energy costs at 12 km·h-1 were correlated with smaller hip flexion (5.5%-12% and 66.5%-74%) and smaller knee flexion (57%-57.5%) during the running gait cycle. Conclusions: This study indicates that biomechanical factors are associated with RE in recreational runners. To design effective training methods to improve RE, coaches and runners should focus on the sagittal plane kinematics of the hip, knee, and ankle, as well as lower vertical and horizontal kinetic parameters. [ABSTRACT FROM AUTHOR]

Purpose: To determine in trained females and males i) the agreement between the gas exchange threshold (GET), lactate threshold 1 (LT1), and heart rate variability threshold 1 (HRVT1), as well as between the respiratory compensation point (RCP), lactate threshold 2 (LT2), and heart rate variability threshold 2 (HRVT2), and ii) the reproducibility of HRVT1 and HRVT2 during 2-min incremental step protocols. Methods: Fifty-seven trained participants (24 females) completed a 2-min step incremental test to task failure. Nineteen participants (eight females) completed a second test to evaluate reproducibility. Gas exchange and ventilatory responses, blood lactate concentration, and RR time series were recorded to assess the oxygen consumption (...) and heart rate (HR) associated with the GET, RCP, LT1, LT2, HRVT1, and HRVT2. Results: /-GET versus ...-HRVT1 and HR-GET versus HR-HRVT1 were statistically different for females (29.5 ± 4.0 vs 34.6 ± 6.1 mL⋅kg-1⋅min-1; 154 ± 11 vs 166 ± 12 bpm) and for males (33.9 ± 4.2 vs 42.7 ± 4.6 mL⋅kg-1·min-1; 145 ± 11 vs 165 ± 9 bpm; P < 0.001). ... and HR at HRVT1 were greater than at LT1 (P < 0.05). ...-RCP versus ...-HRVT2 and HR-RCP versus HR-HRVT2 were not statistically different for females (40.1 ± 4.7 vs 39.5 ± 6.7 mL⋅kg-1⋅min-1; 177 ± 9 vs 176 ± 9 bpm) and males (48.4 ± 5.4 vs 47.8 ± 4.8mL⋅kg-1⋅min-1; 176 ± 8 vs 175 ± 9 bpm; P > 0.05). ... and HR responses at LT2 were similar to HRVT2 (P > 0.05). Intraclass correlation coefficient for .-HRVT1, HR-HRVT1, ...-HRVT2, and HR-HRVT2 indicated good reproducibility when comparing the two different time points to standard methods. Conclusions: Whereas HRVT2 is a valid and reproducible estimate of the RCP/LT2, current approaches for HRVT1 estimation did not show good agreement with outcomes at GET and LT1. [ABSTRACT FROM AUTHOR]

"Super-shoes" are designed to improve endurance running performance by reducing the metabolic demands of running. Although the research on "super-shoes" is still developing and has mostly been studied in male runners, it is not clear how possible mediating factors, such as foot strike pattern, influence the metabolic cost and joint mechanics in competitive female runners. Purpose: The objective of this study is to assess the influence of "super-shoes" on metabolic cost and joint mechanics in competitive female runners and to understand how foot strike patter may influence the footwear effects. Methods: Eighteen competitive female runners ran four 5-min bouts on a force instrumented treadmill at 12.9 km⋅h-1 in 1) Nike Vaporfly Next% 2™(SUPER) and 2) Nike Pegasus 38™(CON) in a randomized and mirrored order. Results: Metabolic power was improved by 4.2% (P < 0.001; d = 0.43) and metatarsophalangeal (MTP) negative work (P < 0.001; d = 1.22), ankle negative work (P = 0.001; d = 0.67), and ankle positive work (P < 0.001; d = 0.97) were all smaller when running in SUPER compared with CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percentage change for metabolic power (r = 0.093, P = 0.715). Conclusions: Metabolic power improved by 4.2% in "super-shoes" (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners, which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in "super-shoes" are consistent with previous literature and may explain or contribute to the metabolic improvements observed in "super-shoes"; however, foot strike pattern was not a moderating factor for the metabolic improvements of "super-shoes." Future studies should directly compare the metabolic response among different types of "super-shoes" between men and women. [ABSTRACT FROM AUTHOR]

Introduction: This study assessed the effect of individualized, domain-based exercise intensity prescription on changes in maximal oxygen uptake (...) and submaximal thresholds. Methods: Eighty-four young healthy participants (42 females, 42males) were randomly assigned to six age, sex, and ...-matched groups (14 participants each). Groups performed continuous cycling in the 1) moderate (MOD), 2) lower heavy (HVY1), and 3) upper heavy-intensity (HVY2) domain; interval cycling in the form of 4) high-intensity interval training (HIIT) in the severe-intensity domain, or 5) sprint-interval training (SIT) in the extreme-intensity domain; or no exercise for 6) control (CON). All training groups, except SIT, were work-matched. Training participants completed three sessions per week for 6 wk with physiological evaluations performed at PRE, MID, and POST intervention. Results: Compared with the change in ... (...) in CON (0.1 ± 1.2 mL⋅kg-1⋅min-1), all training groups, exceptMOD (1.8 ± 2.7 mL⋅kg-1⋅min-1), demonstrated a significant increase ( P < 0.05). HIIT produced the highest increase (6.2 ± 2.8 mL⋅kg-1⋅min-1) followed by HVY2 (5.4 ± 2.3 mL⋅kg-1⋅min-1), SIT (4.7 ± 2.3 mL⋅kg-1⋅min-1), and HVY1 (3.3 ± 2.4 mL⋅kg-1⋅min-1), respectively. The ΔPO at the estimated lactate threshold (θLT) was similar across HVY1, HVY2, HIIT, and SIT, which were all greater than CON (P < 0.05). The ... and ΔPO at θLT for MOD was not different from CON (P > 0.05). HIIT produced the highest ΔPO at maximal metabolic steady state, which was greater than CON, MOD, and SIT (P < 0.05). Conclusions: This study demonstrated that i) exercise intensity is a key component determining changes in ... and submaximal thresholds and ii) exercise intensity domain-based prescription allows for a homogenous metabolic stimulus across individuals. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to determine physiological and metabolic responses to two different sprint interval exercises (SIE) matched for total sprint duration and sprint-rest ratio. Methods: After having measured peak oxygen uptake (...), 14 healthy males (27.1 ± 4.8 yr, 169.6 ± 6.0 cm, 64.5 ± 8.4 kg, ... 47.2 ± 7.7 mL⋅kg-1⋅min-1) performed four 10-s sprints with 80-s recovery (SIE10) and two 20-s sprints with 160-s recovery (SIE20) on different occasions in a counterbalanced crossover manner. Pulmonary ... and changes in tissue oxygenation index (ΔTOI) at vastus lateralis (VL) and rectus femoris (RF) were measured during the SIE. Furthermore, T2-weighted magnetic resonance imaging was taken immediately before and after the SIE to determine the activation levels of VL, RF, vastus medialis, vastus intermedius, adductor magnus, biceps femoris long head, semitendinosus, and semimembranosus at 50% of right thigh length. Results: In SIE10, increases in ... and ΔTOI at VL and RF plateaued after the second sprint, whereas session-averaged ΔTOI was greater in SIE20 than SIE10 in both muscles (VL: 20.9 ± 7.4 vs 14.2% ± 5.9%, RF: 22.8 ± 9.3 vs 12.9% ± 6.6%, P = 0.00). Although both SIE significantly increased T2 values in all eight muscles, those magnitudes were similar between the conditions (SIE10 vs SIE20: 5%-16% vs 8%-16%). Conclusions: This study showed blunted responses of whole-body (...) and peripheral (ΔTOI) oxidative responses with successive sprints (sprint 1 < sprints 2-4) in SIE10, suggesting that increasing sprint repetitions does not necessarily induce greater oxidative metabolism or stimulus. Moreover, greater peripheral oxygen extraction (ΔTOI) was achieved with SIE20, whereas %changes of T2 indicates that the thigh muscles were similarly activated between the SIE conditions. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to examine the recovery kinetics (i.e., time-dependent changes) of performance-related variables between two 120-min male football games performed 3 d apart with and without carbohydrate supplementation. Methods: Twenty male players (20 ± 1 yr; body fat, 14.9% ± 5.1%; maximal oxygen consumption, 59.4 ± 3.7 mL⋅kg-1⋅min-1) participated in two 120-min football games (G1, G2) according to a randomized, two-trial, repeated-measures, crossover, double-blind design. Participants received carbohydrate/placebo supplements during recovery between games. Field activity was monitored during the games. Performance testing and blood sampling were performed before and at 90 and 120 min of each game. Muscle biopsies were collected at baseline and at 90 and 120 min of G1 and pre-G2. Results: Compared with G1, G2 was associated with reduced total distance (10,870 vs 10,685 m during 90 min and 3327 vs 3089 m during extra 30 min; P = 0.007-0.038), average (6.7 vs 6.2 km/h during extra 30-min game-play; P = 0.007) and maximal speed (32.2 vs 30.2 km/h during 90 min and 29.0 vs 27.9 km/h during extra 30 min; P < 0.05), accelerations/decelerations (P < 0.05), and mean heart rate (P < 0.05). Repeated sprint ability (P < 0.001), jumping (P < 0.05), and strength (P < 0.001) performance were compromised before and during G2. Muscle glycogen was not restored at G2 baseline (P = 0.005). Extended game-play reduced lymphocyte, erythrocyte counts, hematocrit, hemoglobin, reduced glutathione (P < 0.05) and increased delayed onset of muscle soreness, creatine kinase activity, blood glycerol, ammonia, and protein carbonyls (P < 0.05) before and during G2. Pax7+ (P = 0.004) and MyoD+ cells (P = 0.019) increased at baseline G2. Carbohydrate supplementation restored performance and glycogen, reduced glycerol and delayed onset of muscle soreness responses, and increased leukocyte counts and Pax7+ and MyoD+ cells. Conclusions: Results suggest that extended football games induce a prolonged recovery of performance, which may be facilitated by carbohydrate supplementation during a congested game fixture. [ABSTRACT FROM AUTHOR]

The step-ramp-step (SRS) can assign constant-load exercise intensities from a ramp-incremental test. Its precision using different moderate-intensity (MOD) steps or ramp slopes has yet to be evaluated. Purpose: To assess whether: i) a lower amplitude constant-load MOD is appropriate to determine the mean response time (MRT); ii) the method accurately corrects the dissociation in the ...O2-PO relationship during ramp compared with constant-load exercise when using different ramp slopes. Methods: Eighteen participants (7 females) performed three SRS tests including: i) step-transitions into MOD from 20 to 50 W (MOD50) and 80 W (MOD80); and ii) slopes of 15, 30, and 45 W⋅min-1. The ...O2 and PO at the gas exchange threshold (GET) and the corrected respiratory compensation point (RCPCORR) were determined. Two to three 30-min constant-load trials evaluated the ...O2 and PO at the maximal metabolic steady state (MMSS). Results: There were no differences in ...O2 at GET (1.97 ±0.36,1.99 ±0.36, 1.95 ±0.30 L⋅min-1), andRCP (2.81 ±0.57,2.86± 0.59,2.84 ±0.59) between 15,30, and 45 W⋅min-1 ramps, respectively (P >0.05). The MRT in seconds was not affected by the amplitude of the MOD or the slope of the ramp (range 19 ± 10 s to 23 ± 20 s; P > 0.05). The mean PO at GET was not significantly affected by the amplitude of the MOD or the slope of the ramp (range 130 ± 30 W to 137 ± 30 W; P > 0.05). The PO at RCPCORR was similar for all conditions ((range 186 ± 43 W to 193 ± 47 W; P > 0.05). Conclusions: The SRS protocol accounts for the ...O2 MRT when using smaller amplitude steps, and for the ...O2 slow component when using different ramp slopes, allowing for accurate partitioning of the exercise intensity domains in a single test. [ABSTRACT FROM AUTHOR]

Within the initial minutes of square-wave exercise transitions above the moderate-intensity domain, the reliance on the anaerobic energy sources may induce some levels of metabolic instability; however, no study has attempted to limit metabolic instability at exercise onset by manipulating the exercise transition phase to a target work rate (WR). Purpose: This study aimed to investigate whether a ramp-to-constant WR (rCWR) transition compared with a square-wave-to-constant WR (CWR) transition within the heavy-intensity domain can reduce metabolic instability and decrease the oxygen cost of exercise. Methods: Fourteen individuals performed (i) a ramp-incremental test to task failure, (ii) a 21-min CWR within the heavy-intensity domain, and (iii) an rCWR to the same WR. Oxygen uptake (...O2), lactate concentration ([La-]), and muscle oxygen saturation (SmO2) were measured. ...O2 and ...O2 gain (...O2-G) during the first 10-min steady-state ...O2 were analyzed. [La-] before, at, and after steady-state ...O2 and SmO2 during the entire 21-min steady-state exercise were also examined. Results: ...O2 and ...O2-G during rCWR (2.49 ± 0.58 L⋅min-1 and 10.7 ± 0.2 mL⋅min-1⋅W-1, respectively) were lower (P < 0.001) than CWR (2.57 ± 0.60 L⋅min-1 and 11.3 ± 0.2 mL⋅min-1⋅W-1, respectively). [La-] before and at steady-state ...O2 during the rCWR condition (1.94 ± 0.60 and 3.52 ± 1.19 mM, respectively) was lower than the CWR condition (3.05 ± 0.82 and 4.15 ± 1.25 mM, respectively) (P <0.001). [La-] dynamics after steady-state ...O2 were unstable for the rCWR (P = 0.011). SmO2 was unstable within the CWR condition from minutes 4 to 13 (P <0.05). Conclusions: The metabolic disruption caused by the initial minutes of square-wave exercise transitions is a primary contributor to metabolic instability, leading to an increased ...O2-G compared with the rCWR condition approach. The reduced early reliance on anaerobic energy sources during the rCWR condition may be responsible for the lower ...O2-G. [ABSTRACT FROM AUTHOR]

Purpose: This study quantified the metabolic demands (oxygen uptake (...O2)), power output adjustments, changes in the ...O2/power output ratio, and perceptual responses (rating of perceived exertion (RPE)) during constant heart rate (HR) exercise performed within the vigorous intensity range (77%-95% HRpeak). Methods: Twelve women (mean ± SD age, 22 ± 4 yr) performed a graded exercise test to exhaustion to determine peak parameters, and three randomly ordered, constant HR trials to exhaustion or for 60 min at the lower (HRL = 77% HRpeak), middle (HRM = 86% HRpeak), and higher (HRH = 95% HRpeak) end of the vigorous intensity range. Time course of changes and patterns of responses were examined for ...O2, power output, ...O2/power output, and RPE for the composite and for each subject. Results: Across the HRL (time to exhaustion (Tlim) = 56.3 ± 9.9 min), HRM (51.8 ± 13.5 min), and HRH (27.2 ± 17.7 min) trials, ...O2 and power output decreased quadratically (P < 0.05) relative to the initial value from 10% to 100% of Tlim, whereas the ...O2/power output increased quadratically from 20% to 100% Tlim and RPE increased linearly from 50% to 100% Tlim. The ...O2 and RPE, collapsed across time, for HRL (54.3% ±3.3% ...O2peak, 11 ± 1.5 RPE) were lower than HRM (64.9% ± 4.5% ...O2peak, 14 ± 1.7 RPE), and both were lower than HRH (80.1% ± 4.1% ...O2peak, 17 ± 1.4 RPE). None of the 12 subjects at HRL, 6 at HRM, and 7 at HRH were within the vigorous ...O2 range. Conclusions: The HRL was not sufficient to meet the desired metabolic intensity for vigorous exercise, whereas the middle to higher end of the range elicited a ...O2 within the prescribed range of only ~50%-60% of the subjects. This study indicated that exercise held constant at a percentage of HRpeak cannot consistently be used to prescribe a desired metabolic stimulus. [ABSTRACT FROM AUTHOR]

Introduction: A recent study showed that cadence modulation during short eccentric cycling exercise affects oxygen consumption (...O2), muscular activity (EMG), and perception of effort (PE). This study examined the effect of cadence on ...O2, EMG, and PE during prolonged eccentric cycling and exercise-induced neuromuscular alterations. Methods: Twenty-two participants completed three sessions 2-3 wk apart: 1) determination of the maximal concentric peak power output, familiarization with eccentric cycling at two cadences (30 and 60 rpm at 60% peak power output), and neuromuscular testing procedure; 2) and 3) 30 min of eccentric cycling exercise at a cadence of 30 or 60 rpm. PE, cardiorespiratory parameters, and vastus lateralis and rectus femoris EMG were collected during exercise. The knee extensors' maximal voluntary contraction torque, the torque evoked by double stimulations at 100 Hz (Dt100) and 10 Hz (Dt10), and the voluntary activation level were evaluated before and after exercise. Results: ...O2, EMG, and PE were greater at 30 than 60 rpm (all P <0.05). Maximal voluntary contraction torque, evoked torque, and Dt10/Dt100 ratio decreased (all P < 0.01) without cadence effect (all P > 0.28). Voluntary activation level remained constant after both eccentric cycling exercises (P = 0.87). Conclusions: When performed at the same power output, eccentric cycling exercise at 30 rpm elicited a greater PE, EMG, and cardiorespiratory demands than pedaling at 60 rpm. Exercise-induced fatigability was similar in both eccentric cycling conditions without neural impairments, suggesting that eccentric cycling seemed to alter more specifically muscular function, such as the excitation-contraction coupling process. In a rehabilitation context, eccentric cycling at 60 rpm seems more appropriate because it will induce lower PE for similar strength loss compared with 30 rpm. [ABSTRACT FROM AUTHOR]

Introduction: Previous studies ranging from 2 to 12 wk of sprint interval training (SIT) have reported improvements in maximal oxygen uptake (...O2max) and neuromuscular function in sedentary populations. However, whether the time course of the changes in these variables correlates with greater training volumes is unclear. Methods: Thirteen sedentary participants performed three all-out training weekly sessions involving 15-s sprints interspersed with 2 min of recovery on a cycle ergometer. The 6-wk training program was composed of three identical blocks of 2 wk in which training volume was increased from 10 to 14 repetitions over the first four sessions and reduced to 8 in the last session. The power output and the heart rate (HR) were monitored during the sessions. The ...O2max, the power-force-velocity profile, and the isometric force were assessed every 2 wk from baseline. Results: A significant increase in ...O2max was observed from the second week plateauing thereafter despite four additional weeks of training. The dynamic force production increased from the second week, and the speed production decreased by the end of the protocol. The isometric force and the maximal power output from the power-force-velocity profile did not change. Importantly, the time spent at high percentages of the maximal HR during the training sessions was lower in the second and third training block compared with the first. Conclusions: SIT resulted in an effective approach for rapidly increasing ...O2max, and no change in the isometric force was found; cycling-specific neuromuscular adaptations were observed from the second week of training. SIT may be useful in the short term, but further improvement of overall physical fitness might need other training modalities like endurance and/or resistance training. [ABSTRACT FROM AUTHOR]

Purpose: Long-chain omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) may enhance recovery from exercise-induced muscle damage (EIMD). However, it is unclear if the effects are due to EPA, DHA, or both. The purpose of this investigation was to examine the effect of EPA + DHA, EPA, and DHA compared with placebo (PL) on muscular recovery. Methods: Thirty males were randomized to 4 g·d−1 EPA + DHA (n = 8), EPA (n = 8), DHA (n = 7), or PL (n = 7). After 7-wk supplementation, a downhill running (20 min, 70% V̇O2max, −16% gradient) plus jumping lunges (5 × 20 reps, 2-min rest intervals) muscle damage protocol was performed. Indices of muscle damage, soreness, muscle function, and inflammation were measured at baseline and throughout recovery. The omega-3 index (O3i; %EPA + %DHA in erythrocytes) was used to track tissue EPA and DHA status. Results: After supplementation, the O3i was significantly higher than PL in all experimental groups (P < 0.001). Leg press performance was lower in the PL group at 24 h compared with EPA (P = 0.019) and at 72 h for EPA (P = 0.004) and DHA (P = 0.046). Compared with PL, muscle soreness was lower in the DHA (P = 0.015) and EPA (P = 0.027) groups at 48 h. Albeit nonsignificant, EPA + DHA tended to attenuate muscle soreness (d = 1.37) and leg strength decrements (d = 0.75) compared with PL. Jump performance and power metrics improved more rapidly in the EPA and DHA groups (time effects: P < 0.001). Measures of inflammation, range of motion, and muscle swelling were similar between groups (P > 0.05). Conclusions: Compared with PL, 4 g·d−1 of EPA or DHA for 52 d improves certain aspects of recovery from EIMD. EPA + DHA did not clearly enhance recovery. Equivalent dosing of EPA + DHA may blunt the performance effects observed in EPA or DHA alone. [ABSTRACT FROM AUTHOR]

The article critiques the idea that rapid red blood cell (RBC) transit times through pulmonary capillaries contribute significantly to exercise-induced arterial hypoxemia (EIAH), citing evidence from both animal and human studies to refute this claim. It also discusses the limitations of the Multiple Inert Gas Elimination Technique (MIGET) in pinpointing the exact causes of diffusion limitations and highlights the role of endurance training in stabilizing pulmonary capillary blood volume.

Purpose: The purpose of this study is to characterize both the efficacy of altered restriction pressures and consequences of optimized blood flow restriction (BFR) for altering the cardiovascular and fluid regulating response in humans. Methods: This work comprised a series of related trials. Phase 1: during semi-recumbent cycling (5 min, 60 W) with BFR at 0%, 50%, 75%, 100%, and 125% of participants' lowest arterial occlusion pressure (LOP) echocardiographic images were collected alongside continuous heart rate (HR) and blood pressure (BP). In phase 2, 24 h fluid balance (intake-output) and fluid-regulating hormone responses were measured after a practical BFR exercise session (treadmill walking: 5·3 min, 1 min rest, 5 km·h−1, 5% incline, 100% LOP). Phase 3 examined the magnitude and effect of blood volume distribution following BFR treadmill walking using a modified CO-rebreathe technique. Results: Cardiac ejection fraction remained stable irrespective of cuff pressure and despite a reduction in end-diastolic volume (Δ of 11 ± 9 mL, P = 0.02). HR and BP were highest at 100% LOP (ΔHR = 18 ± 19 bpm, ΔSBP = 51 ± 30 mm Hg, ΔDBP = 33 ± 15 mm Hg, ΔRate Pressure Product = 76 ± 32 bpm·mm Hg·100−1). BFR treadmill walking stimulated a greater release of fluid-regulating hormones than normal walking (Δrenin = BFR: 25.3 ± 24.2 vs CON: 9.1 ± 11.8 ng·L−1; Δcopeptin = BFR: 50.1 ± 97.9 vs. CON: 0.43 ± 0.8 pmol·L−1), but no difference in fluid retention was observed (P = 0.2). Approximately 27% of total blood volume was confined to the legs during BFR, but the relative volume trapped in the legs was not related to fluid-regulating hormone release (renin r = −0.04, P = 0.9; copeptin r = 0.27, P = 0.3). Conclusions: BFR exercise elicits the largest cardiovascular effect using 100% LOP, with evidence of appreciable fluid regulating hormonal response during a typical BFR exercise session. The relative volume of blood sequestered in the limb does not appear to drive this response. [ABSTRACT FROM AUTHOR]

Purpose: The kinetics of physiological responses to exercise have traditionally been characterized by estimating exponential equation parameters using iterative best-fit techniques of heart rate (HR) and gas exchange (respiratory rate, oxygen uptake (V̇O2), carbon dioxide output, and ventilation). In this study, we present a novel approach to characterizing the maturation of physiological responses to exercise in children by accounting for response uncertainty and variability. Methods: Thirty-seven early-pubertal (17 females, 20 males) and 44 late-pubertal (25 females, 19 males) participants performed three multiple brief exercise bouts (MBEB). MBEB consisted of ten 2-min bouts of cycle ergometry at constant work rate interspersed by 1-min rest. Exercise intensity was categorized as low, moderate, or high, corresponding to 40%, 60%, and 80% of peak work rate, and performed in random order on 3 separate days. We evaluated sample entropy (SampEn), approximate entropy, detrended fluctuation analysis, and average absolute local variability of HR and gas exchange. Results: SampEn of HR and gas-exchange responses to MBEB was greater in early- compared with late-pubertal participants (e.g., V̇O2 early-pubertal vs late-pubertal, 1.70 ± 0.023 vs 1.41 ± 0.027; P = 2.97 × 10−14), and decreased as MBEB intensity increased (e.g., 0.37 ± 0.01 HR for low-intensity compared with 0.21 ± 0.014 for high intensity, P = 3.56 × 10−17). Females tended to have higher SampEn than males (e.g., 1.61 ± 0.025 V̇O2 for females vs 1.46 ± 0.031 for males, P = 1.28 × 10−4). Average absolute local variability was higher in younger participants for both gas exchange and HR (e.g., early-pubertal vs late-pubertal V̇O2, 17.48 % ± 0.56% vs 10.24 % ± 0.34%; P = 1.18 × 10−21). Conclusions: The greater entropy in signal response to a known, quantifiable exercise perturbation in the younger children might represent maturation-dependent, enhanced competition among physiological controlling mechanisms that originate at the autonomic, subconscious, and cognitive levels. [ABSTRACT FROM AUTHOR]

Iron Absorption in Highly Trained Male Runners: Does it Matter When and Where You Eat Your Iron?. Med. Sci. Sports Exerc., Vol. 56, No. 1, pp. 118-127, 2024. Purpose: We examined iron absorption and its regulation during two common scenarios experienced by endurance athletes. Our aims were to: (i) compare the effects of preexercise versus postexercise iron intake on iron absorption; and (ii) compare the impact of training at altitude (1800 m) on iron absorption preexercise. Methods: Male runners (n = 18) completed three exercise trials over a 5-wk period, each preceded by 24 h of standardized low-iron diets. First, athletes completed two 60-min treadmill running trials at 65% VO˙ 2max at near sea-level (580 m). In a randomized order, preexercise and postexercise test meals labeled with 4 mg of 57Fe or 58Fe were consumed 30 min before or 30 min after exercise. Then, the same exercise trial was performed after living and training at altitude (~1800 m) for 7 d, with the labeled test meal consumed 30 min preexercise. We collected venous blood samples preexercise and postexercise for markers of iron status and regulation, and 14 d later to measure erythrocyte isotope incorporation. Results: No differences in fractional iron absorption were evident when test meals were consumed preexercise (7.3% [4.4, 12.1]) or postexercise (6.2% [3.1, 12.5]) (n = 18; P = 0.058). Iron absorption preexercise was greater at altitude (18.4% [10.6, 32.0]) than at near sea-level (n = 17; P < 0.001) and hepcidin concentrations at altitude were lower at rest and 3 h postexercise compared with near sea level (P < 0.001). Conclusions: In an acute setting, preexercise and postexercise iron absorption is comparable if consumed within 30 min of exercise. Preexercise iron absorption increases 2.6-fold at altitude compared with near sea-level, likely due to the homeostatic response to provide iron for enhanced erythropoiesis and maintain iron stores. [ABSTRACT FROM AUTHOR]

Are There Interindividual Responses of Cardiovascular Disease Risk Markers to Acute Exercise? A Replicate Crossover Trial. Med. Sci. Sports Exerc., Vol. 56, No. 1, pp. 63-72, 2024. Purpose: Using a replicated crossover design, we quantified the response heterogeneity of postprandial cardiovascular disease risk marker responses to acute exercise. Methods: Twenty men (mean (SD) age, 26 (6) yr; body mass index, 23.9 (2.4) kg·m−2 ) completed four 2-d conditions (two control, two exercise) in randomized orders. On days 1 and 2, participants rested and consumed two high-fat meals over 9 h. Participants ran for 60 min (61 (7)% of peak oxygen uptake) on day 1 (6.5 to 7.5 h) of both exercise conditions. Time-averaged total area under the curve (TAUC) for triacylglycerol, glucose, and insulin were calculated from 11 venous blood samples on day 2. Arterial stiffness and blood pressure responses were calculated from measurements at baseline on day 1 and at 2.5 h on day 2. Consistency of individual differences was explored by correlating the two replicates of control-adjusted exercise responses for each outcome. Within-participant covariate-adjusted linear mixed models quantified participant-by-condition interactions and individual response SDs. Results: Acute exercise reduced mean TAUC-triacylglycerol (−0.27 mmol·L-1 ·h; Cohen’s d = 0.29, P = 0.017) and TAUC-insulin (−25 pmol·L-1 ·h; Cohen’s d = 0.35, P = 0.022) versus control, but led to negligible changes in TAUC-glucose and the vascular outcomes (Cohen’s d ≤ 0.36, P ≥ 0.106). Small-to-moderate, but nonsignificant, correlations were observed between the two response replicates (r = −0.42 to 0.15, P ≥ 0.066). We did not detect any individual response heterogeneity. All participant-by-condition interactions were P ≥ 0.137, and all individual response SDs were small with wide 95% confidence intervals overlapping zero. Conclusions: Large trial-to-trial within-subject variability inhibited detection of consistent interindividual variability in postprandial metabolic and vascular responses to acute exercise. [ABSTRACT FROM AUTHOR]

HAPI Fit: An Exercise Intervention to Improve Peak Aerobic Capacity in Young Adults Born Very Preterm. Med. Sci. Sports Exerc., Vol. 56, No. 1, pp. 44-52, 2024. Introduction: Individuals born preterm have reduced aerobic capacity, which could be related to impaired organ development. Their capacity to improve aerobic capacity with exercise training could therefore be limited, but this remains unknown. We aimed to test an exercise intervention to improve cardiorespiratory fitness in adults born preterm. Methods: Twenty-one very preterm and 37 full-term individuals aged 18–33 yr took part in a 14-wk supervised exercise intervention of cardiovascular, resistance, and flexibility training (two group and one individual sessions per week). Adherence and compliance to intervention were recorded. Primary outcome was change in peak oxygen consumption (peak VO˙ 2) measured before and after the intervention. Within- and between-group differences were estimated using nonparametric tests. Results: Of 219 eligible individuals, 58 were enrolled and 14 participants dropped out over the course of the intervention. Among the 44 who completed the intervention, mean adherence was 82% and 66% for group and individual sessions, respectively. Compliance with training requirement varied between 71% and 100%. There was no difference in adherence between the preterm and full-term groups. Because only one preterm male met the adherence criteria, subsequent analyses were done exclusively on females. Both the term and preterm groups achieved higher peak VO˙ 2 after the intervention [term = +4.2 (SD 4.3) mL·min-1 ·kg-1, P < 0.01; preterm = +4.7 (2.9) mL·min-1 ·kg-1, P < 0.01]. There was no between-group difference in the response to the intervention (P = 0.729). Conclusions: Recruitment and adherence to an exercise intervention are challenging. Results could indicate improvements in cardiorespiratory fitness in young women born preterm after current exercise program. Adaptation of this intervention is needed for wider uptake. [ABSTRACT FROM AUTHOR]

Introduction/purpose: Previous results about shoe longitudinal bending stiffness (LBS) and running economy (RE) show high variability. This study aimed to assess the effects of shoes with increased LBS on RE and performance in trained and national runners. Methods: Twenty-eight male runners were divided into two groups according to their 10-km performance times (trained, 38-45 min and national runners, <34 min). Subjects ran 2 - 3 min (at 9 and 13 km·h-1 for trained, and 13 and 17 km·h-1 for national runners) with an experimental shoe with carbon fiber plate to increase the LBS (Increased LBS) and a control shoe (without carbon fiber plate). We measured energy cost of running (W·kg-1) and spatiotemporal parameters in visit one and participants performed a 3000 m time trial (TT) in two successive visits. Results: Increased LBS improved RE in the trained group at slow (11.41 ± 0.93 W·kg-1 vs 11.86 ± 0.93 W·kg-1) and fast velocity (15.89 ± 1.24 W·kg--1 vs 16.39 ± 1.24 W·kg-1) and only at the fast velocity in the national group (20.35 ± 1.45 W·kg-1 vs 20.78 ± 1.18 W·kg-1). The improvements in RE were accompanied by different changes in biomechanical variables between groups. There were a similar improvement in the 3000 m TT test in Increased LBS for trained (639 ± 59 vs 644 ± 61 s in control shoes) and national runners (569 ± 21 vs 574 ± 21 s in control shoes)withmore constant pace in increased LBS compared with control shoes in both groups. Conclusions: Increasing shoe LBS improved RE at slow and fast velocities in trained runners and only at fast velocity in national runners. However, the 3000m TT test improved similarly in both levels of runners with increased LBS. The improvements in RE are accompanied by small modifications in running kinematics that could explain the difference between the different levels of runners. [ABSTRACT FROM AUTHOR]