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Purpose: To investigate differences in time to exhaustion (TTE), O2 uptake ( V ˙ O 2 ), and accumulated O2 deficit ( O 2 def ) between competitive and recreational cross-country (XC) skiers during an intermittent-interval protocol standardized for maximal aerobic power (MAP). Methods: Twelve competitive (maximal V ˙ O 2 [ V ˙ O 2 max ] = 76.5 ± 3.8 mL · kg − 1 · min − 1 ) and 10 recreational ( V ˙ O 2 max = 63.5 ± 6.3 mL · kg − 1 · min − 1 ) male XC skiers participated. All tests were performed on a rollerski treadmill in the V2 ski-skating technique. To quantify MAP and maximal accumulated oxygen deficit (MAOD), the skiers performed a steady-state submaximal test followed by a 1000-m time trial. After a 60-minute break, TTE, V ˙ O 2 , and accumulated O 2 def were measured during an intermittent-interval protocol (40-s work and 20-s recovery), which was individually tailored to 120% and 60% of each subject's MAP. Results: During the 1000-m time trial, the competitive skiers had 21% (95% CI, 12%–30%) shorter finish time and 24% (95% CI, 14%–34%) higher MAP (all P <.01) than the recreational skiers. No difference was observed in relative exercise intensity (average power/MAP; P =.28), MAOD (P =.18), or fractional utilization of V ˙ O 2 max. During the intermittent-interval protocol, the competitive skiers had 34% (95% CI, 3%–65%) longer TTE (P =.03) and accumulated 61% (95% CI, 27%–95%) more O 2 def (P =.001) than the recreational skiers during work phases. Conclusions: Competitive XC skiers have longer TTE and accumulate more O 2 def than recreational XC skiers during an intermittent-interval protocol at similar intensity relative to MAP. This implies that performance in intermittent endurance sports is related to the ability to repeatedly recharge fractions of MAOD. [ABSTRACT FROM AUTHOR]

Purpose: To measure oxygen demand, uptake, and deficits in competitive cross-country skiers during outdoor roller skiing at different competition durations, ranging from the endurance domain to the sprint domain. Methods: Ten competitive cross-country skiers (6 males; V ˙ O2max 78 ± 3 and 4 females; V ˙ O2max 62 ± 3 mL∙kg−1∙min−1) raced time trials consisting of 1, 2, and 4 laps in a 1.6 km racecourse in a randomized order with 35 min recovery in-between. Oxygen uptake was measured using a wearable metabolic system while oxygen demand was estimated from kinematic data (GPS and IMU) and an athlete-specific model of skiing economy. Skiing economy and V ˙ O2max was established on a separate test day using six submaximal constant-load trials at different speeds and inclines, and one maximal-effort trial on a roller-skiing treadmill. Results: Average oxygen demand was 112 ± 8%, 103 ± 7% and 98 ± 7% of V ˙ O2max during the 1 (3:37 ± 0:20 m:ss), 2 (7:36 ± 0:38 m:ss) and 4 (15:43 ± 1:26 m:ss) lap time trials, respectively, and appeared to follow an inverse relationship with time-trial duration. Average oxygen uptake was unaffected by race length (86 ± 5%, 86 ± 5%, and 86 ± 7% of V ˙ O2max, respectively). Accumulated oxygen deficit at the end of each time trial was 85 ± 13, 106 ± 32 and 158 ± 62 mL∙kg−1, while oxygen deficits per work bout was 23 ± 3, 18 ± 3 and 16 ± 3 mL∙kg−1 for the 1, 2, and 4-lap time trials, respectively. Conclusion: Elite cross-country skiers adjust their pacing strategies from attaining relatively small oxygen deficits per work bout in the endurance domain, to larger deficits in the sprint domain. This indicates a shift in strategy from prioritizing stable work-economy and rate-of-recovery in the endurance domain, to maximizing power output in the sprint domain. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) plays a pivotal role in sustaining marine ecosystems. The Bohai Sea in China is a semi-enclosed sea, and oxygen-deficit events occur from time to time due to human activities. At present, there is a notable absence of any convenient and precise method for obtaining three-dimensional spatial data on DO, and the exploration of the physical mechanisms influencing oxygen deficit remains incomplete. This investigation uses the linear radial basis function (RBF-Linear) fitting method to conduct three-dimensional spatial interpolation for DO, which demonstrates minimal inaccuracy. Then, the RBF-Linear fitting method is utilized to collect a comprehensive three-dimensional spatial dataset encompassing temperature, salinity, and DO in the Bohai Sea in August from 2016 to 2018. The results indicate discernible interannual variations in the extent, area, and distribution of oxygen deficiency during summer in the Bohai Sea. Mechanism analysis reveals that intense precipitation episodes and an increase in wind stress curl exacerbate oxygen depletion. Additionally, the degree, location, and area of the two oxygen-deficit cores (off the Yellow River Estuary and off the Qinhuangdao) in the Bohai Sea are influenced by several factors, including current velocity, direction, local circulation position, and net horizontal transport rate. Furthermore, the study suggests that oxygen deficiency in the Bohai Sea region is currently in its early stages, with a limited degree of injury and a restricted range of influence. The use of a three-dimensional spatial interpolation method to create a complete DO field in three-dimensional space simplifies the research challenges associated with marine oxygen deficit. Moreover, this study holds particular significance for guiding the development of marine fisheries. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to develop and validate a bioenergetic model describing the dynamic behavior of the alactic, lactic, and aerobic metabolic energy supply systems as well as different sources of the total metabolic energy demand. Methods: The bioenergetic supply model consisted of terms for the alactic, lactic, and aerobic system metabolic rates while the demand model consisted of terms for the corresponding metabolic rates of principal cycling work, pulmonary ventilation, and accumulated metabolites. The bioenergetic model was formulated as a system of differential equations and model parameters were estimated by a non-linear grey-box approach, utilizing power output and aerobic metabolic rate (MRae) data from fourteen cyclists performing an experimental trial (P2) on a cycle ergometer. Validity was assessed by comparing model simulation and measurements on a similar follow-up experimental trial (P3). Results: The root mean square error between modelled and measured MRae was 61.9 ± 7.9 W and 79.2 ± 30.5 W for P2 and P3, respectively. The corresponding mean absolute percentage error was 8.6 ± 1.5% and 10.6 ± 3.3% for P2 and P3, respectively. Conclusion: The validation of the model showed excellent overall agreement between measured and modeled MRae during intermittent cycling by well-trained male cyclist. However, the standard deviation was 38.5% of the average root mean square error for P3, indicating not as good reliability. [ABSTRACT FROM AUTHOR]

Abstract Drought and flooding occur at opposite ends of the soil moisture spectrum yet their resulting stress responses in plants share many similarities. Drought limits root water uptake to which plants respond with stomatal closure and reduced leaf gas exchange. Flooding limits root metabolism due to soil oxygen deficiency, which also limits root water uptake and leaf gas exchange. As drought and flooding can occur consecutively in the same system and resulting plant stress responses share similar mechanisms, a single theoretical framework that integrates plant responses over a continuum of soil water conditions from drought to flooding is attractive. Based on a review of recent literature, we integrated the main plant eco‐physiological mechanisms in a single theoretical framework with a focus on plant water transport, plant oxygen dynamics, and leaf gas exchange. We used theory from the soil–plant–atmosphere continuum modeling as “backbone” for our framework, and subsequently incorporated interactions between processes that regulate plant water and oxygen status, abscisic acid and ethylene levels, and the resulting acclimation strategies in response to drought, waterlogging, and complete submergence. Our theoretical framework provides a basis for the development of mathematical models to describe plant responses to the soil moisture continuum from drought to flooding.

Abstract Introduction Since sex-specific accumulated oxygen deficit (AOD) during high-intensity swimming remains unstudied, this study aimed to assess AOD during 50, 100, and 200 m front-crawl performances to compare the responses between sexes and analyse the effect of lean body mass (LBM). Methods Twenty swimmers (16.2 ± 2.8 years, 61.6 ± 7.8 kg, and 48.8 ± 11.2 kg LBM—50% males) performed 50, 100, and 200 m to determine accumulated oxygen uptake (V̇O2Ac). The swimmers also performed an incremental test from which five submaximal steps were selected to estimate the oxygen demand (V̇O2demand) from the V̇O2 versus velocity adjustment. V̇O2 was sampled using a gas analyser coupled with a respiratory snorkel. AOD was the difference between V̇O2demand and V̇O2Ac, and LBM (i.e. lean mass not including bone mineral content) was assessed by dual-energy X-ray absorptiometry (DXA). Results A two-way ANOVA evidenced an AOD increase with distance for both sexes: 19.7 ± 2.5 versus 24.9 ± 5.5, 29.8 ± 8.0 versus 36.5 ± 5.8, and 41.5 ± 9.4 versus 5.2 ± 11.9 ml × kg−1, respectively, for 50, 100, and 200 m (with highest values for females, P

Drought and flooding occur at opposite ends of the soil moisture spectrum yet their resulting stress responses in plants share many similarities. Drought limits root water uptake to which plants respond with stomatal closure and reduced leaf gas exchange. Flooding limits root metabolism due to soil oxygen deficiency, which also limits root water uptake and leaf gas exchange. As drought and flooding can occur consecutively in the same system and resulting plant stress responses share similar mechanisms, a single theoretical framework that integrates plant responses over a continuum of soil water conditions from drought to flooding is attractive. Based on a review of recent literature, we integrated the main plant eco‐physiological mechanisms in a single theoretical framework with a focus on plant water transport, plant oxygen dynamics, and leaf gas exchange. We used theory from the soil–plant–atmosphere continuum modeling as "backbone" for our framework, and subsequently incorporated interactions between processes that regulate plant water and oxygen status, abscisic acid and ethylene levels, and the resulting acclimation strategies in response to drought, waterlogging, and complete submergence. Our theoretical framework provides a basis for the development of mathematical models to describe plant responses to the soil moisture continuum from drought to flooding. [ABSTRACT FROM AUTHOR]

Recent work suggests that Oxygen Minimum Zones (OMZs) are sustained by the supply of oxygen‐poor waters rather than the export of organic matter from the local surface layer and its subsequent remineralization inside OMZs. However, the mechanisms that form and maintain OMZs are not well constrained, such as the origin of the oxygen that oxygenates OMZs, and the locations where oxygen consumption occurs. Here we use an observation‐based transport matrix to determine the origins of open ocean OMZs in terms of (a) OMZ volume, (b) oxygen that survives remineralization and oxygenates OMZs, and (c) oxygen utilization in the interior ocean that contributes to the oxygen‐deficit of OMZs. We also determine where the utilization of oxygen occurs along the pathways that ventilate the OMZs. Our results show that about half of the volume of OMZ waters originate in high‐latitude regions, but most of their oxygen is utilized for remineralization before they reach OMZs. Instead, OMZs are mostly oxygenated by tropical, subtropical and intermediate waters formed in nearby regions. More than half of the utilization of oxygen occurs in the tropics and subtropics, while less than a third occurs within the OMZs themselves. We therefore suggest that, in steady‐state, OMZs are primarily set by ocean circulation pathways that high‐latitude deep and old water upwards, with relatively low oxygen content. Plain Language Summary: Oxygen Minimum Zones (OMZs) are regions in the ocean where the dissolved oxygen concentration is low enough that many animals cannot survive there. It is uncertain what processes dominate the formation of OMZs because oxygen measurements only tell us about their deficit in oxygen, not where the oxygen loss occurred. Recent studies suggest that the oxygen is consumed in waters away from the OMZs and then these oxygen‐poor waters are transported inside. However, the exact locations where the oxygen consumption occurs are still uncertain. Here we use a model built on observations to show where the oxygen is coming from and where it is consumed. We find that most of the oxygen in the OMZs is coming from young waters originating in nearby regions, while old waters that are low in oxygen come from distant, high‐latitude regions. The latter suggests that oxygen consumption originates outside the OMZs and is then transported inside, agreeing with previous studies. About half of this consumption occurs as waters resurface in the tropics and subtropics where they are exposed to organic matter. We also find that the location of the OMZs is determined mainly from where water masses that sink in the high latitudes eventually resurface. Key Points: We determine the origins of Oxygen Minimum Zones (OMZs) in terms of sources of volume, oxygen, and oxygen‐deficitHigh‐latitude source regions have a key role in feeding OMZs with oxygen‐deficit, at centennial to millennial timescalesThe oxygen‐deficit in the OMZs originates mostly from remineralization outside the OMZs [ABSTRACT FROM AUTHOR]

Despite the development of biorefinery processes, the possibility of coupling the "conventional" composting process with the production of biochemicals is not taken into account. However, net carbon monoxide (CO) production has been observed during bio-waste composting. So far, O2 concentration and temperature have been identified as the main variables influencing CO formation. This study aimed to investigate CO net production during bio-waste composting under controlled laboratory conditions by varying aeration rates and temperatures. A series of composting processes was carried out in conditions ranging from mesophilic to thermophilic (T = 35, 45, 55, and 65 °C) and an aeration rate of 2.7, 3.4, 4.8, and 7.8 L·h−1. Based on the findings of this study, suggestions for the improvement of CO production throughout the composting process have been developed for the first time. The highest concentrations of CO in each thermal variant was achieved with an O2 deficit (aeration rate 2.7 L·h−1); additionally, CO levels increased with temperature, reaching ~300 ppm at 65 °C. The production of CO in mesophilic and thermophilic conditions draws attention to biological CO formation by microorganisms capable of producing the CODH enzyme. Further research on CO production efficiency in these thermal ranges is necessary with the characterization of the microbial community and analysis of the ability of the identified bacteria to produce the CODH enzyme and convert CO from CO2. [ABSTRACT FROM AUTHOR]

Introduction: Since sex-specific accumulated oxygen deficit (AOD) during high-intensity swimming remains unstudied, this study aimed to assess AOD during 50, 100, and 200 m front-crawl performances to compare the responses between sexes and analyse the effect of lean body mass (LBM). Methods: Twenty swimmers (16.2 ± 2.8 years, 61.6 ± 7.8 kg, and 48.8 ± 11.2 kg LBM—50% males) performed 50, 100, and 200 m to determine accumulated oxygen uptake (V̇O2Ac). The swimmers also performed an incremental test from which five submaximal steps were selected to estimate the oxygen demand (V̇O2demand) from the V̇O2 versus velocity adjustment. V̇O2 was sampled using a gas analyser coupled with a respiratory snorkel. AOD was the difference between V̇O2demand and V̇O2Ac, and LBM (i.e. lean mass not including bone mineral content) was assessed by dual-energy X-ray absorptiometry (DXA). Results: A two-way ANOVA evidenced an AOD increase with distance for both sexes: 19.7 ± 2.5 versus 24.9 ± 5.5, 29.8 ± 8.0 versus 36.5 ± 5.8, and 41.5 ± 9.4 versus 5.2 ± 11.9 ml × kg−1, respectively, for 50, 100, and 200 m (with highest values for females, P < 0.01). Inverse correlations were observed between LBM and AOD for 50, 100, and 200 m (r = − 0.60, − 0.38 and − 0.49, P < 0.05). AOD values at 10 and 30 s elapsed times in each trial decreased with distance for both sexes, with values differing when female swimmers were compared to males in the 200 m trial (at 10 s: 2.6 ± 0.6 vs. 3.4 ± 0.6; and at 30 s: 7.9 ± 1.7 vs. 10.0 ± 1.8 ml × kg−1, P < 0.05). Conclusion: LBM differences between sexes influenced AOD values during each trial, suggesting that reduced muscle mass in female swimmers plays a role on the higher AOD (i.e. anaerobic energy) demand than males while performing supramaximal trials. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) plays a pivotal role in sustaining marine ecosystems. The Bohai Sea in China is a semi-enclosed sea, and oxygen-deficit events occur from time to time due to human activities. At present, there is a notable absence of any convenient and precise method for obtaining three-dimensional spatial data on DO, and the exploration of the physical mechanisms influencing oxygen deficit remains incomplete. This investigation uses the linear radial basis function (RBF-Linear) fitting method to conduct three-dimensional spatial interpolation for DO, which demonstrates minimal inaccuracy. Then, the RBF-Linear fitting method is utilized to collect a comprehensive three-dimensional spatial dataset encompassing temperature, salinity, and DO in the Bohai Sea in August from 2016 to 2018. The results indicate discernible interannual variations in the extent, area, and distribution of oxygen deficiency during summer in the Bohai Sea. Mechanism analysis reveals that intense precipitation episodes and an increase in wind stress curl exacerbate oxygen depletion. Additionally, the degree, location, and area of the two oxygen-deficit cores (off the Yellow River Estuary and off the Qinhuangdao) in the Bohai Sea are influenced by several factors, including current velocity, direction, local circulation position, and net horizontal transport rate. Furthermore, the study suggests that oxygen deficiency in the Bohai Sea region is currently in its early stages, with a limited degree of injury and a restricted range of influence. The use of a three-dimensional spatial interpolation method to create a complete DO field in three-dimensional space simplifies the research challenges associated with marine oxygen deficit. Moreover, this study holds particular significance for guiding the development of marine fisheries.

Purpose: The aim of this study was to develop a new, easy-to-set-up method for estimating the relationship between the contributions of the anaerobic and aerobic energy systems in athletes performing the Wingate Anaerobic Test (WAnT). Methods: A parallel registration of WAnT parameters and oxygen consumption, measured breath by breath, was conducted. Thus, the indicators of the activity of the aerobic and anaerobic systems ensuring the physical effort were calculated. Participants and Results: Twelve soccer players, 14 years of age; height 164,7±8,0 cm; body weight 50,7±9,2 kg, were tested twice, before and after 5 months specialized training program focused on the improvement of speed/power and endurance. Statistically significant increase was found in: Total power output by 16,4%; O2 deficit by 32,4%; O2 deficit/O2 excess by 80,3% in favor of the deficit. Conclusion: The results indicate that the physiological parameters highly sensitive and reflect strong associations with the metabolic changes in response to the training training program, compared to the ergometric ones. [ABSTRACT FROM AUTHOR]

Purpose: τ of the primary phase of V ˙ O 2 A kinetics during square-wave, moderate-intensity exercise mirrors that of PCr splitting (τPCr). Pre-exercise [PCr] and the absolute variations of PCr (∆[PCr]) occurring during transient have been suggested to control τPCr and, in turn, to modulate V ˙ O 2 A kinetics. In addition, V ˙ O 2 A kinetics may be slower when exercise initiates from a raised metabolic level, i.e., from a less-favorable energetic state. We verified the hypothesis that: (i) pre-exercise [PCr], (ii) pre-exercise metabolic rate, or (iii) ∆[PCr] may affect the kinetics of muscular oxidative metabolism and, therefore, τ. Methods: To this aim, seven active males (23.0 yy ± 2.3; 1.76 m ± 0.06, V ˙ O 2 max : 3.32 L min−1 ± 0.67) performed three repetitions of series consisting of six 6-min step exercise transitions of identical workload interspersed with different times of recovery: 30, 60, 90, 120, 300 s. Results: Mono-exponential fitting was applied to breath-by-breath V ˙ O 2 A , so that τ was determined. τ decays as a first-order exponential function of the time of recovery (τ = 109.5 × e(−t/14.0) + 18.9 r2 = 0.32) and linearly decreased as a function of the estimated pre-exercise [PCr] (τ = − 1.07 [PCr] + 44.9, r2 = 0.513, P < 0.01); it was unaffected by the estimated ∆[PCr]. Conclusions: Our results in vivo do not confirm the positive linear relationship between τ and pre-exercise [PCr] and ∆[PCr]. Instead, V ˙ O 2 A kinetics seems to be influenced by the pre-exercise metabolic rate and the altered intramuscular energetic state. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the effect of exercise-induced hyperpnea on gross efficiency (GE) and anaerobic capacity estimates during a self-paced 3-min supramaximal cycle time trial (TT). Fourteen highly trained male cyclists performed 7 × 4-min submaximal stages, a 6-min passive rest, a 3-min TT, a 5-min passive rest, and a 6-min submaximal stage. Three models were based on the 7 × 4-min linear regression extrapolation method, using 1) the conventional model (7−YLIN); 2) the same 7−YLIN model but correcting for the additional ventilatory cost (i.e., hyperpnea) (7−YLIN-V-cor); and 3) accounting for linearly declining GE during the TT (7−YLIN-D). The other three models were based on GE from the last submaximal stage, using the conventional model (GELAST) and the same modifications as described for 7+YLIN, i.e., 1) GELAST, 2) GELAST-V-cor, and 3) GELAST-D. The GELAST model generated 18% higher values of anaerobic capacity than the 7−YLIN model (P < 0.05). During the TT, the hyperpnea-corrected model (i.e., 7-YLIN-V-cor or GELAST-V-cor) generated, compared with the respective conventional model (i.e., 7-YLIN or GELAST), ∼0.7 percentage points lower GE and ∼11% higher anaerobic capacity (all, P < 0.05). The post-TT GE was 1.9 percentage points lower (P < 0.001) and the 7-YLIN-D or GELAST-D model generated, compared with the respective conventional model, a lower GE (∼1.0 percentage points) and ∼17% higher anaerobic capacity during the TT (all, P < 0.05). In conclusion, the correction for a declining GE due to hyperpnea during a supramaximal TT resulted in an increased required total metabolic rate and anaerobic energy expenditure compared with the conventional models. [ABSTRACT FROM AUTHOR]

In this research work, environmental monitoring processes and assessments are carried out by the modeling and analysis of the water quality of the Chambal River in the state of Rajasthan. Various samples were collected from different locations along the course of the river flow. This water is used for different kinds of human, animal, and agriculture corp. activities. Comparative analyses were conducted on the water parameters, viz. biochemical oxygen demand, chemical oxygen demand, dissolved oxygen, total coliform, and conductivity, for the of consecutive years 2020 and 2021. A model was developed with the help of MATLAB Simulink software (Version R2019a) to find the causes of oxygen deficiency and reoxygenation in water with time and distance. The results of two consecutive years help to predict the responsible factors for the degradation of the river's water quality. The water quality modeling and simulation results conclude that the water quality of the Chambal River flowing through Rajasthan can rejuvenate itself during an alarming oxygen deficit within a short period. According to the results of this study, the concentration of dissolved oxygen in the water of the Chambal River is high enough to support the survival of the endangered species that inhabit the area. [ABSTRACT FROM AUTHOR]

International Journal of Exercise Science 15(7): 599-615, 2022. The anaerobic metabolism determination is complex and the applied methodologies present limitations. Thus, the purpose of this study was to investigate the effects of different calculations (MAOD vs. AOD) on the anaerobic contribution using the dynamic knee extension. Twenty-four male were recruited [Mean (SD); age 27 (1) years, body mass 90 (3) kg, height 181 (2) cm]. This study was divided into two independent experiments (EXP1: one-legged; EXP2: two-legged). In both experiments, it was performed a graded exercise test to determine maximal power (MP-GXT); 2-4 submaximal efforts (VO2-intensity relationship); and an exhaustive effort. The theoretical energy demand for the exhaustive effort (TEDex) was constructed from the submaximal efforts. Therefore, MAOD was assumed as the difference between the TEDex and the accumulated VO2 (AVO2). In contrast, the energy demand for AOD was calculated as the product between VO2 at the end of exercise and time to exhaustion (TEDaod). Thus, AOD was assumed as the difference between TEDaod and AVO2. Bayesian paired t-test was used to compare the differences between the applied methods. Also, correlations between the anaerobic indices and performance were verified. In EXP1, AOD was higher than MAOD [1855 (741) vs. 434 (245); BF10 = 2925; ES = 2.5]. In contrast, in EXP2, MAOD was higher than AOD [2832 (959) vs. 1636 (549); BF10 = 3.33; ES = 1.4]. Also, AOD was correlated to performance (r = .59; BF10 = 4.38). We concluded that MAOD and AOD are a distinct phenomenon and must be utilized according to the exercise model. [ABSTRACT FROM AUTHOR]

The current study aimed to compare time spent above 90% V̇O 2max (tV̇O 2max) during 3 work-matched interval training protocols comprising 8×60-second exercise efforts with decreasing, increasing, or constant work rate distribution within each exercise interval. Ten healthy male subjects (age: 27.6±5.0 years; V̇O 2max: 3.82±0.52 L•min–1) performed an incremental test to determine V̇O 2max and peak power output (P max). During visits 2, 3, and 4, three work-matched interval training sessions comprising 8×60 s efforts: 60 s active recovery with the power output held constant (100%Pmax; ITCON), decreasing (from 110 to 90%Pmax; ITDEC), or increasing (from 90 to 110%Pmax; ITINC) linearly throughout each work interval. Time sustained above 90% of V̇O 2max (tV̇O 2max) or HRmax (tHRmax), blood lactate concentrations (BLC) and rating of perceived exertion (RPE) were measured. The tV̇O 2max (ITCON: 274±132; ITDEC: 313±102; ITINC: 310±113 s, P=0.37), tHRmax (ITCON: 396±180; ITDEC: 441±207; ITINC: 390±212 s, P=0.47), BLC (P=0.73), and final RPE (P=0.75) were similar among protocols. In conclusion, work-matched interval training induced similar time near V̇O 2max and associated physiological responses regardless of work rate manipulation. [ABSTRACT FROM AUTHOR]

Low oxygen breathing has been the subject of considerable research in recent years. The present review aims to determine the physiological and neuropsychological benefits of lowoxygen training. Specifically, we explored the ways low oxygen affects hormones, neurotransmitters and growth factors responsible for neuroplasticity, higher cognition and positive emotions. In addition, we shed light on the importance of hypoxia to expand the conscious experience. Furthermore, we investigate the role of digital technologies in assisting hypoxic training. The results showed that, when hypoxia occurs, the human body puts into action the amazing survival mission which reveals unexplored alternative plans and healing pathways. Oxygen deprivation, under certain circumstances, has beneficial effects on cognition, mood and consciousness. It was observed an increase in growth factors, which are responsible for tissue repair and regeneration. Hypoxia also was found to stimulate the hormones of pleasure, happiness, pain tolerance, socialization and relaxation. Interestingly, people under hypoxic conditions are more likely to have transcendental experiences -even to develop ‘superhuman’ abilities. Digital technologies facilitate the safe implementation of hypoxic training enabling users to take control of a powerful tool, which is none other than breathing. Metacognition in breathing can help people consciously and safely manipulate their breathing by moving themselves away from their comfort zone and exploring new pathways to rewire their brains and plumb the depths of their physical, cognitive, emotional and spiritual potential. Our findings suggest that hypoxic training could be an effective intervention strategy with important therapeutic benefits for people with learning and other disabilities (i.e adhd, memory deficits, autism, motor, impairments, depression, generalized anxiety disorder). Future educators, therapists and families should be trained to appropriate apply simple hypoxic training exercises even in the educational context. For that reason, research into the physiological and neuropsychological mechanism that is affected by hypoxic training for individuals with learning or other disabilities is necessary. [ABSTRACT FROM AUTHOR]

AIM: To investigate the change of macular pigment optical density(MPOD)in the patients of obstructive sleep apnea-hypopnea syndrome(OSAHS). METHODS: Totally 70 OSAHS patients as observation group and 32 healthy subjects as control group with their right eyes were enrolled from Chongqing Emergency Medical Center during January to December of 2019. All the subjects used Visucam 200 to measure the mean/max MPOD. RESULTS: Both mean/max MPOD(0.0916±0.0149, 0.2675±0.0419Log unit)of OSAHS group are significantly lower than the control group(0.1193±0.0159, 0.3235±0.0400Log unit, Pn=12)/moderate(n=17)/severe(n=41)groups divided by AHI(Pr=-0.685, -0.492; PCONCLUSION: Our study results suggest that the mean/max MPOD were reduced in the patients of OSAHS. Moreover, the decreased degree of mean/max MPOD is positively related to the severity of OSAHS. It shows that the MPOD of OSAHS have already changed before they feel the significant syndrome. The reducing of MPOD may cause dysfunction of macular and finally rise up to macular disease.

Atom probe tomography (APT) is emerging as a key nanogeochemistry technique for diverse geoscience applications. Estimating stoichiometric mineral compositions is particularly challenging for features at nanoscale. APT provides reliable measurements for metallic systems but the reliability for oxides is problematic, notably due to oxygen deficit. Here, we use laser‐assisted APT to compare results for spinel and garnet crystals. APT compositional results were compared with those by electron microprobe to determine the possible APT analytical inaccuracy. Extensive data processing was accomplished, including correlation histograms, 2D ion distribution maps and 1D elements concentration profiles, to disclose the possible mechanisms leading to mineral stoichiometry biases. Multiple events and neutral molecules formation are probable the main processes responsible for atom deficit. In particular, the amount of the same isotope–same charge state ion pairs correlated with aluminium and oxygen deficits suggests that the co‐evaporation in a dead space–dead time window could lead to a significant decrease of detected ions. Also, molecular species dissociation and direct current evaporation could partially account for further atom loss. Overall, better APT compositional estimation was obtained for spinel, which has lesser variation in lattice sites and greater overall lattice symmetry, higher thermal conductivity and lower band gap compared with garnet. [ABSTRACT FROM AUTHOR]

Purpose: To reach top performance in cycling, optimizing distribution of energy resources is crucial. The purpose of this study was to investigate power output during 250-m, 500-m, and 1000-m cycling time trials and the characteristics of the adopted pacing strategy. Methods: Nine trained cyclists completed an incremental test and 3 time trials that they were instructed to finish as quickly as possible. Preceding the trials, peak power during short sprints (PPsprint) and gross efficiency (GE) were measured. During the trials, power output and oxygen consumption were measured to calculate the contribution of the aerobic and anaerobic energy sources. After the trial GE was measured again. Results: Peak power during all trials (PPTT) was lower than PPsprint. In the 250-m trial the PPTT was higher in the 1000-m trial (P = .008). The subjects performed a significantly longer time at high intensity in the 250-m than in the 1000-m (P = .029). GE declined significantly during all trials (P < .01). Total anaerobically attributable work was less in the 250-m than in the 500-m (P = .015) and 1000-m (P < .01) trials. Conclusion: The overall pacing pattern in the 250-m trial appears to follow an all-out strategy, although peak power is still lower than the potential maximal power output. This suggests that a true all-out pattern of power output may not be used in fixed-distance events. The 500-m and 1000-m had a more conservative pacing pattern and anaerobic power output reached a constant magnitude. [ABSTRACT FROM AUTHOR]

Allergic asthma is a typical chronic inflammatory disease of respiratory tract. Clinical data shows that patients with allergic asthma have different degrees of cognitive dysfunction. The molecular mechanism underlying the pathogenesis of asthma-induced cognitive disorder is not yet well defined. Dexamethasone (DEX), one of the first-line drugs being widely used in the treatment of asthma, has not been reported to have an effect on cognitive dysfunction in mice model. To investigate the effect of asthma on cognitive impairment as well as the effect of DEX on asthma-caused morphological and behavioral changes, C57BL/6J mice received treatment with house dust mites (HDM) for 60 days to become allergic asthma model mice, and a group of HDM-treated asthma model mice were treated with DEX. HDM-treated asthma model mice exhibited increased airway hyperresponsiveness (AHR) and inflammatory infiltration in lung tissue. An elevated level of IL-4, IL-5, and TNF-α was detected in bronchoalveolar lavage fluid (BALF) by Luminex liquid suspension chip. Asthma model mice also presented memory deficits accompanied with morphological changes at the synaptic levels in the cortex and hippocampus. Meanwhile, vascular edema and increased expression of HIF-1α and HIF-2α were found in the brain of asthma model mice. Interestingly, DEX treatment could reverse the inflammatory changes in asthma model mice airway, rescue the cognitive impairment and improve the synaptic plasticity. Besides, DEX significantly decreased the expression of HIF-1α and HIF-2α in mice brain and lung. These processes may be used to decipher the complex interplay and pathological changes between asthma and cognition. This study provides laboratory evidence for the prevention and treatment of cognitive malfunction induced by asthma.

Key points: Females have lower fatigability than males during single limb isometric and dynamic contractions, but whether sex‐differences exist during high‐intensity whole‐body exercise remains unknown.This study shows that males and females respond similarly to repeated supramaximal whole‐body exercise, and that at task failure a large functional reserve remains in both sexes.Using post‐exercise ischaemia with repeated exercise, we have shown that this functional reserve depends on the glycolytic component of substrate‐level phosphorylation and is almost identical in both sexes.Metaboreflex activation during post‐exercise ischaemia and the O2 debt per kg of active lean mass are also similar in males and females after supramaximal exercise.Females have a greater capacity to extract oxygen during repeated supramaximal exercise and reach lower PETCO2, experiencing a larger drop in brain oxygenation than males, without apparent negative repercussion on performance.Females had no faster recovery of performance after accounting for sex differences in lean mass. The purpose of this study was to ascertain what mechanisms explain sex differences at task failure and to determine whether males and females have a functional reserve at exhaustion. Exercise performance, cardiorespiratory variables, oxygen deficit, and brain and muscle oxygenation were determined in 18 males and 18 females (21–36 years old) in two sessions consisting of three bouts of constant‐power exercise at 120% of V̇O2max until exhaustion interspaced by 20 s recovery periods. In one of the two sessions, the circulation of both legs was occluded instantaneously (300 mmHg) during the recovery periods. Females had a higher muscle O2 extraction during fatiguing supramaximal exercise than males. Metaboreflex activation, and lean mass‐adjusted O2 deficit and debt were similar in males and females. Compared to males, females reached lower PETCO2 and brain oxygenation during supramaximal exercise, without apparent negative consequences on performance. After the occlusions, males and females were able to restart exercising at 120% of V̇O2max, revealing a similar functional reserve, which depends on glycolytic component of substrate‐level phosphorylation and its rate of utilization. After ischaemia, muscle O2 extraction was increased, and muscle V̇O2 was similarly reduced in males and females. The physiological response to repeated supramaximal exercise to exhaustion is remarkably similar in males and females when differences in lean mass are considered. Both sexes fatigue with a large functional reserve, which depends on the glycolytic energy supply, yet females have higher oxygen extraction capacity, but reduced PETCO2 and brain oxygenation. Key points: Females have lower fatigability than males during single limb isometric and dynamic contractions, but whether sex‐differences exist during high‐intensity whole‐body exercise remains unknown.This study shows that males and females respond similarly to repeated supramaximal whole‐body exercise, and that at task failure a large functional reserve remains in both sexes.Using post‐exercise ischaemia with repeated exercise, we have shown that this functional reserve depends on the glycolytic component of substrate‐level phosphorylation and is almost identical in both sexes.Metaboreflex activation during post‐exercise ischaemia and the O2 debt per kg of active lean mass are also similar in males and females after supramaximal exercise.Females have a greater capacity to extract oxygen during repeated supramaximal exercise and reach lower PETCO2, experiencing a larger drop in brain oxygenation than males, without apparent negative repercussion on performance.Females had no faster recovery of performance after accounting for sex differences in lean mass. [ABSTRACT FROM AUTHOR]

Allergic asthma is a typical chronic inflammatory disease of respiratory tract. Clinical data shows that patients with allergic asthma have different degrees of cognitive dysfunction. The molecular mechanism underlying the pathogenesis of asthma-induced cognitive disorder is not yet well defined. Dexamethasone (DEX), one of the first-line drugs being widely used in the treatment of asthma, has not been reported to have an effect on cognitive dysfunction in mice model. To investigate the effect of asthma on cognitive impairment as well as the effect of DEX on asthma-caused morphological and behavioral changes, C57BL/6J mice received treatment with house dust mites (HDM) for 60 days to become allergic asthma model mice, and a group of HDM-treated asthma model mice were treated with DEX. HDM-treated asthma model mice exhibited increased airway hyperresponsiveness (AHR) and inflammatory infiltration in lung tissue. An elevated level of IL-4, IL-5, and TNF-α was detected in bronchoalveolar lavage fluid (BALF) by Luminex liquid suspension chip. Asthma model mice also presented memory deficits accompanied with morphological changes at the synaptic levels in the cortex and hippocampus. Meanwhile, vascular edema and increased expression of HIF-1α and HIF-2α were found in the brain of asthma model mice. Interestingly, DEX treatment could reverse the inflammatory changes in asthma model mice airway, rescue the cognitive impairment and improve the synaptic plasticity. Besides, DEX significantly decreased the expression of HIF-1α and HIF-2α in mice brain and lung. These processes may be used to decipher the complex interplay and pathological changes between asthma and cognition. This study provides laboratory evidence for the prevention and treatment of cognitive malfunction induced by asthma. [ABSTRACT FROM AUTHOR]

When using a new noninvasive method for measuring the efficiency of pulmonary gas exchange, a key measurement is the oxygen deficit, defined as the difference between the end-tidal alveolar PO2 and the calculated arterial PO2. The end-tidal PO2 is measured using a rapid gas analyzer, and the arterial PO2 is derived from pulse oximetry after allowing for the effect of the PCO2 on the oxygen affinity of hemoglobin. In the present report we show that the values of end-tidal PO2 and PCO2 are highly reproducible, providing a solid foundation for the measurement of the oxygen deficit. We compare the oxygen deficit with the classical ideal alveolar-arterial PO2 difference (A-aDO2) as originally proposed by Riley, and now extensively used in clinical practice. This assumes Riley’s criteria for ideal alveolar gas, namely no ventilation-perfusion inequality, the same PCO2 as arterial blood, and the same respiratory exchange ratio as the whole lung. It transpires that, in normal subjects, the end-tidal PO2 is essentially the same as the ideal value. This conclusion is consistent with the very small oxygen deficit that we have reported in young normal subjects, the significantly higher values seen in older normal subjects, and the much larger values in patients with lung disease. We conclude that this noninvasive measurement of the efficiency of pulmonary exchange is identical in many respects to that based on the ideal alveolar PO2, but that it is easier to obtain. [ABSTRACT FROM AUTHOR]

When using a new noninvasive method for measuring the efficiency of pulmonary gas exchange, a key measurement is the oxygen deficit, defined as the difference between the end-tidal alveolar PO2 and the calculated arterial PO2. The end-tidal PO2 is measured using a rapid gas analyzer, and the arterial PO2 is derived from pulse oximetry after allowing for the effect of the PCO2 on the oxygen affinity of hemoglobin. In the present report we show that the values of end-tidal PO2 and PCO2 are highly reproducible, providing a solid foundation for the measurement of the oxygen deficit. We compare the oxygen deficit with the classical ideal alveolar-arterial PO2 difference (A-aDO2) as originally proposed by Riley, and now extensively used in clinical practice. This assumes Riley’s criteria for ideal alveolar gas, namely no ventilation-perfusion inequality, the same PCO2 as arterial blood, and the same respiratory exchange ratio as the whole lung. It transpires that, in normal subjects, the end-tidal PO2 is essentially the same as the ideal value. This conclusion is consistent with the very small oxygen deficit that we have reported in young normal subjects, the significantly higher values seen in older normal subjects, and the much larger values in patients with lung disease. We conclude that this noninvasive measurement of the efficiency of pulmonary exchange is identical in many respects to that based on the ideal alveolar PO2, but that it is easier to obtain. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Purpose: This study aimed to quantify the repeated oxygen deficits attained during intermittent endurance exercise by measuring oxygen consumption (V˙O2) and oxygen demand (V˙O2dem) throughout a simulated roller ski race. Methods: Eight male elite cross-country skiers (V˙O2peak, 77.4 ± 4.4 mL·kg−1⋅min−1) raced a 13.5-km roller ski time trial on a World Cup course. On two additional days, athletes completed (i) six submaximal loads (~5 min) and ~4-min maximal trial to establish athlete-specific estimates of skiing economy, V˙O2peak, and maximal ΣO2def (MAOD); and (ii) a simulation of the time trial on a roller skiing treadmill. During the simulation, external work rate (P prop) and skiing speed (v) were adjusted to match the P prop and v measured during the time trial, and pulmonary V˙O2 was measured breath by breath. V˙O2dem and ΣO2def were calculated using an athlete-specific model for skiing economy throughout the treadmill simulation. Results: During the treadmill simulation, V˙O2 was on average 0.77 V˙O2peak, and active V˙O2dem (i.e., excluding the time in simulated downhill) was on average 1.01 V˙O2peak. The athletes repeatedly attained substantial oxygen deficits in individual uphill sections of the treadmill simulation, but the deficits were typically small compared with their MAOD (average 14%, range ~0%–50%). However, the ΣO2def summed over all periods of active propulsion was on average 3.8 MAOD. Conclusion: Athletes repeatedly attain substantial oxygen deficits in the uphill segments of a distance cross-country ski race. Furthermore, the total accumulated oxygen deficit of all these segments is several times higher than the athletes' MAOD. This suggests that the rapid recovery of the energy stores represented by the oxygen deficit is necessary during downhill sections, and that this might be an important determinant of distance skiing performance. [ABSTRACT FROM AUTHOR]

The Wingate Anaerobic Test (WAnT) is the most commonly used test for the assessment of anaerobic power and anaerobic capacity of athletes. The well known parameters recorded during the WAnT routine procedure in our opinion could be subjected to additional analysis generating substantial additional physiological data. The aim of this study was to develop a new, easy to set up method estimating the relationship between the contribution of the anaerobic and aerobic energy systems in athletes performing WAnT. A parallel registration of WAnT parameters and the oxygen consumption breath by breath was done. Thus, the indicators for the activity of the aerobic and anaerobic systems, ensuring the physical ef-fort in each segment (in seconds) of the test, were calculated. The proposed method was introduced and applied to twelve soccer players, 14years of age; height164,7±8,0cm; body weight50,7±9,2kg; maxi-mal heart rate195,7±7,0bpm; maximal oxygen uptake58,1±9,9ml.kg-1. Participants were tested twice, before and after 5 months specialized training program focussed on the improvement of speed/power and endurance. Statistically significant progress was found in: Total power output by 16,4%; O2 deficit by 32,4%; O2 deficit/O2 excess by 80,3% in favor of the deficit. It was established that the differences in the calculated physiological parameters during the performance of the WAnT before and after the five-month training program are more pronounced compared to the ergometric ones, especially with regard to the participation of each system in energy processes. The results indicate that the proposed physiological parameters are of high sensitivity and reflect strong associations with the metabolic changes in response to the training modalities. The method is easy to implement, allowing quick analysis of the individual results and its application in exercise physiology laboratories and the sports practice could be beneficial.

The purpose of this study was to assess the physical work demand in relation to metrics of force and subsequent physiological response to a simulated flatwater slalom competition. Eight New Zealand team members completed a standard incremental step-test to ascertain power:oxygen consumption relationship. This was followed by a simulated race run where breath-by-breath analysis along with force and power data logged at 50 Hz to determine stroke length, impulse, peak force, time to peak force, and rate of peak force per stroke. Physiological response to negotiating a flatwater slalom course was greater than straight-line paddling (36.89 ± 2.01 vs. 32.17 ± 1.97 ml⋅kg-1⋅min-1, p = 0.0065) at the same power output. Mean power output for the duration of the simulated race (91.63 ± 7.19 s) was 203.8 ± 45.0 W, incurring an oxygen deficit of 1.386 ± 0.541 L⋅min-1 translating to an overall anaerobic contribution of 32 ± 18% and aerobic contribution of 68 ± 18%. Moderate to strong relationships between time duration and stroke peak force (R2 = 0.354, R2 = 0.485) and rate of peak force development (R2 = 0.345, R2 = 0.426) but not for stroke length (R2 = 0.022, R2 = 0.012), impulse (R2 = 0.088, R2 = 0.097) or time to peak force (R2 = 0.001, R2 = 0.0001) for left and right strokes, respectively. The number of propulsive (0.6 s) strokes with a ratio of 94:6%. Longer stroke duration was significantly correlated to greater impulse (R2 = 0.507, p < 0.0001) and time to peak force (R2 = 0.851, p < 0.0001), but a lower rate of force development (R2 = 0.107, p < 0.0001). The results show that a flatwater slalom under simulated race conditions entails initial supra-maximal (anaerobic) work rate with a subsequent transition to one associated with maximal aerobic capacity. Inability to sustain work done and the subsequent decline in peak force and force profile per stroke requires further research regarding strategies to enhance performance.

Nitrification of the environment has resulted from tremendous increases in the use of fertilizers for crop plants. This has increased runoff to coastal marine areas with consequences for primary production, benthos and upper trophic-level consumers, including sea ducks such as eiders Somateria mollissima. This species primarily relies on filter-feeding bivalves, especially blue mussels Mytilus edulis. Stable isotopes of nitrogen (measured as δ15N) are incorporated in the feathers of eiders during molt at a constant rate reflecting the amount in food eaten. We examined if δ15N values in feathers can link eiders to the nitrogen loads in the marine waters surrounding Denmark, which is the main wintering grounds for the Baltic/Wadden Sea eider population. We also assessed how the abundance of eiders is related to nutrients and dead zones with oxygen deficit. During 2014–2018 we collected samples from 489 eiders, and of these 100 were analyzed for stable isotopes δ15N. Eider feather δ15N was positively related to nitrogen abundance in marine waters. Local aggregations of eiders in late summer (the molting period) and in winter increased with the amount of nitrogen in the marine environment. Large eiders took longer to molt, they molted later and the daily growth increments of feathers were larger. Finally, larger eiders and eiders in higher numbers occurred in areas with hypoxia. These findings show that anthropogenic inputs to the coastal marine environment positively influence the abundance and aggregations of eiders. [ABSTRACT FROM AUTHOR]

Energy system contribution during cross-country (XC) skiing races is dependent on several factors, including the race duration, track profile, and sub-techniques applied, and their subsequent effects on the use of the upper and lower body. This review provides a scientific synopsis of the interactions of energy system contributions from a physiological, technical, and tactical perspective. On average, the aerobic proportion of the total energy expended during XC skiing competitions is comparable to the values for other sports with similar racing times. However, during both sprint (≤ 1.8 km) and distance races (≥ 10 and 15 km, women and men, respectively) a high aerobic turnover interacts with subsequent periods of very high work rates at ~ 120 to 160% of VO2peak during the uphill sections of the race. The repeated intensity fluctuations are possible due to the nature of skiing, which involves intermittent downhills where skiers can recover. Thus, the combination of high and sustained aerobic energy turnover and repeated work rates above VO2peak, interspersed with short recovery periods, distinguishes XC skiing from most other endurance sports. The substantially increased average speed in races over recent decades, frequent competitions in mass starts and sprints, and the greater importance of short periods at high speeds in various sub-techniques, have demanded changes in the physiological, technical, and tactical abilities needed to achieve world-class level within the specific disciplines. [ABSTRACT FROM AUTHOR]

• A new excessive moisture stress factor was developed and added into APSIM-soybean. • The addition of this factor was more important in simulating root growth than the exact parameterization. • Vertical root growth is inhibited when volumetric soil moisture approaches 3% below saturation. • Root depth and length distributions were affected by the depth to the water table. Shallow water table (WT) influences crop growth and production in many major agricultural regions across the globe. We enhanced the APSIM-soybean model to accurately simulate root depth in fields with shallow water tables. We used data from a controlled experiment (Rhizotron facilities) that included root depth observations for nine WT treatments to develop and calibrate the new model. Analysis indicated that unconstrained root growth occurs until volumetric soil moisture approaches 0.03 mm/mm below saturation. Below that threshold, root growth linearly decreases to zero at saturation. Inclusion of this factor into the model increased accuracy of root depth simulations from R2 of 0.65 to 0.97 and reduced root mean square error from 45 to 9 cm. Validation of root depth simulations using independent field data from Iowa, USA (years 2016, 2017, 2018) confirmed the model. We also found that the inhibition of root growth in response to shallow WT substantially impacted the vertical distribution of the roots in both measurements and simulations. Overall, this work enhances the capability of APSIM in simulating production and environmental aspects of cropping systems, especially in regions with shallow water tables typical of the Corn Belt, USA. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the physical work demand in relation to metrics of force and subsequent physiological response to a simulated flatwater slalom competition. Eight New Zealand team members completed a standard incremental step-test to ascertain power:oxygen consumption relationship. This was followed by a simulated race run where breath-by-breath analysis along with force and power data logged at 50 Hz to determine stroke length, impulse, peak force, time to peak force, and rate of peak force per stroke. Physiological response to negotiating a flatwater slalom course was greater than straight-line paddling (36.89 ± 2.01 vs. 32.17 ± 1.97 ml⋅kg-1⋅min-1, p = 0.0065) at the same power output. Mean power output for the duration of the simulated race (91.63 ± 7.19 s) was 203.8 ± 45.0 W, incurring an oxygen deficit of 1.386 ± 0.541 L⋅min-1 translating to an overall anaerobic contribution of 32 ± 18% and aerobic contribution of 68 ± 18%. Moderate to strong relationships between time duration and stroke peak force (R 2 = 0.354, R 2 = 0.485) and rate of peak force development (R 2 = 0.345, R 2 = 0.426) but not for stroke length (R 2 = 0.022, R 2 = 0.012), impulse (R 2 = 0.088, R 2 = 0.097) or time to peak force (R 2 = 0.001, R 2 = 0.0001) for left and right strokes, respectively. The number of propulsive (<0.6 s) strokes outweighed turning/driving (>0.6 s) strokes with a ratio of 94:6%. Longer stroke duration was significantly correlated to greater impulse (R 2 = 0.507, p < 0.0001) and time to peak force (R 2 = 0.851, p < 0.0001), but a lower rate of force development (R 2 = 0.107, p < 0.0001). The results show that a flatwater slalom under simulated race conditions entails initial supra-maximal (anaerobic) work rate with a subsequent transition to one associated with maximal aerobic capacity. Inability to sustain work done and the subsequent decline in peak force and force profile per stroke requires further research regarding strategies to enhance performance. [ABSTRACT FROM AUTHOR]

Summary Objectives The present study analyzes the impact of a strength training program on bioenergetics parameters determined at velocity corresponding to maximal oxygen uptake (v V ˙ O 2 max). Methods Sixteen recreational long-distance runners were divided into strength training (STG, n = 9) and control (CG, n = 7) groups. Before and after 8 weeks, the volunteers performed: maximal incremental treadmill test, constant-speed running at pre-training v V ˙ O 2 max , and maximum dynamic strength test (1RM). Energy cost of running (ECr), and aerobic (A MET) and anaerobic (AN MET) metabolism contributions were estimated at v V ˙ O 2 max. Results No differences were observed at baseline between groups (P > 0.05). After experimental period, there was an increase in 1RM for STG (27 ± 18%, P = 0.008), but not for CG (P > 0.05). The changes in ECr (pre = 0.254 ± 0.038 vs. post = 0.255 ± 0.037 kJ·m−1), A MET (pre = 191.5 ± 26.2 vs. post = 193.0 ± 31.7 kJ), and AN MET (pre = 20.9 ± 6.4 vs. post = 21.0 ± 5.7 kJ) were not significant different (P > 0.05) to STG; as well as to CG (ECr - pre = 0.260 ± 0.046 vs. post = 0.259 ± 0.034 kJ·m−1, A MET - pre = 209.7 ± 30.2 vs. post = 203.3 ± 26.6 kJ, and AN MET - pre = 19.3 ± 6.4 vs. post = 23.9 ± 4.6 kJ). Conclusions These findings suggest that 8 weeks strength training improved the maximum dynamic strength and did not alter bioenergetics parameters measured at v V ˙ O 2 max in recreational endurance runners. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to compare the contributions of the anaerobic pathway as determined by two different methods and energy expenditure during a typical high-intensity intermittent exercise (HIIE) protocol.Methods: A descriptive research design was utilized in which thirteen physically active men performed six experimental sessions consisting of an incremental test (session 1), submaximal tests at 40, 50, 60, 70, 75, 80, 85, 90% of velocity associated with maximum oxygen uptake (vV˙O2max) with two intensities per session (sessions 2–5), and the HIIE protocol (session 6; 10 efforts of 1 min at vV˙O2max interspersed by 1 min of passive recovery). The estimation of anaerobic energy system contribution was calculated by: (a) the excess post-exercise oxygen consumption plus delta lactate method and (b) the accumulated oxygen deficit method using the difference between predicted oxygen demand from the submaximal tests of varying intensities and accumulated oxygen uptake during HIIE. Estimation of aerobic energy system contribution was calculated through the measurement of oxygen consumption during activity. Total EE during the entire HIIE protocol (efforts + recovery) and for the efforts only were calculated from each method.Results: For efforts + recovery and efforts only, anaerobic contribution was similar for both methods, and consequently total EE was also equivalent (p = 0.230 for both comparisons). During efforts + recovery, aerobic:anaerobic energy system contribution was (68 ± 4%: 32 ± 4%), while efforts only was (54 ± 5%: 46 ± 5%) with both situations demonstrating greater aerobic than anaerobic contribution (p < 0.001 for both).Conclusion: Anaerobic contribution seems to be relevant during HIIE and must to be taken into account during total EE estimation; however, the type of method employed did not change the anaerobic contribution or total EE estimates.

Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise.Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7°) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O2 deficit (MAOD) method the V.O2-speed regression relationship was used to estimate the V.O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline V.O2. The gross efficiency (GE) method (method 3) involved calculating metabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a V.O2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate V.O2 demand during the TT.Results: The GE/EC remained constant across the submaximal stages and the supramaximal TT was performed in 185 ± 24 s. The GE and EC methods produced identical V.O2 demands and O2 deficits. The V.O2 demand was ~3% lower for the 4+Y method compared with the 4-Y and GE/EC methods, with corresponding O2 deficits of 56 ± 10, 62 ± 10, and 63 ± 10 mL·kg−1, respectively (P < 0.05 for 4+Y vs. 4-Y and GE/EC). The mean differences between the estimated O2 deficits were −6 ± 5 mL·kg−1 (4+Y vs. 4-Y, P < 0.05), −7 ± 1 mL·kg−1 (4+Y vs. GE/EC, P < 0.05) and −1 ± 5 mL·kg−1 (4-Y vs. GE/EC), with respective typical errors of 5.3, 1.9, and 6.0%. The mean difference between the O2 deficit estimated with GE/EC based on the average of four submaximal stages compared with the last stage was 1 ± 2 mL·kg−1, with a typical error of 3.2%.Conclusions: These findings demonstrate a disagreement in the O2 deficits estimated using current methods. In addition, the findings suggest that a valid estimate of the O2 deficit may be possible using data from only one submaximal stage in combination with the GE/EC method.

Purpose: The aim of the present study was to compare the contributions of the anaerobic pathway as determined by two different methods and energy expenditure during a typical high-intensity intermittent exercise (HIIE) protocol. Methods: A descriptive research design was utilized in which thirteen physically active men performed six experimental sessions consisting of an incremental test (session 1), submaximal tests at 40, 50, 60, 70, 75, 80, 85, 90% of velocity associated with maximum oxygen uptake (v V ˙ O2max) with two intensities per session (sessions 2–5), and the HIIE protocol (session 6; 10 efforts of 1 min at v V ˙ O2max interspersed by 1 min of passive recovery). The estimation of anaerobic energy system contribution was calculated by: (a) the excess post-exercise oxygen consumption plus delta lactate method and (b) the accumulated oxygen deficit method using the difference between predicted oxygen demand from the submaximal tests of varying intensities and accumulated oxygen uptake during HIIE. Estimation of aerobic energy system contribution was calculated through the measurement of oxygen consumption during activity. Total EE during the entire HIIE protocol (efforts + recovery) and for the efforts only were calculated from each method. Results: For efforts + recovery and efforts only, anaerobic contribution was similar for both methods, and consequently total EE was also equivalent (p = 0.230 for both comparisons). During efforts + recovery, aerobic:anaerobic energy system contribution was (68 ± 4%: 32 ± 4%), while efforts only was (54 ± 5%: 46 ± 5%) with both situations demonstrating greater aerobic than anaerobic contribution (p < 0.001 for both). Conclusion: Anaerobic contribution seems to be relevant during HIIE and must to be taken into account during total EE estimation; however, the type of method employed did not change the anaerobic contribution or total EE estimates. [ABSTRACT FROM AUTHOR]

Using a case study, this article reviews the health risks associated with prolonged sitting and the reasons sedentary workers are at risk for musculoskeletal injuries. Other health issues associated with prolonged sitting or sedentary behavior as well as the benefits of exercise are also explored. Finally, evidence-based interventions to reduce health risks associated with prolonged sitting may increase productivity. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise. Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7◦) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O2 deficit (MAOD) method the ˙VO2-speed regression relationship was used to estimate the O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline O2. The gross efficiency (GE) method (method 3) involved calculatingmetabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a O2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate O2 demand during the TT. Results: The GE/EC remained constant across the submaximal stages and the supramaximal TT was performed in 185 ± 24 s. The GE and EC methods produced identical O2 demands and O2 deficits. The O2 demand was ∼3% lower for the 4+Y method compared with the 4-Y and GE/EC methods, with corresponding O2 deficits of 56 ± 10, 62 ± 10, and 63 ± 10 mL·kg-1, respectively (P < 0.05 for 4+Y vs. 4-Y and GE/EC). The mean differences between the estimated O2 deficits were -6 ± 5 mL·kg-1 (4+Y vs. 4-Y, P < 0.05), -7 ± 1 mL·kg-1 (4+Y vs. GE/EC, P < 0.05) and -1 ± 5 mL·kg-1 (4-Y vs. GE/EC), with respective typical errors of 5.3, 1.9, and 6.0%. The mean difference between the O2 deficit estimated with GE/EC based on the average of four submaximal stages compared with the last stage was 1 ± 2 mL·kg-1, with a typical error of 3.2%. Conclusions: These findings demonstrate a disagreement in the O2 deficits estimated using current methods. In addition, the findings suggest that a valid estimate of the O2 deficit may be possible using data from only one submaximal stage in combination with the GE/EC method. [ABSTRACT FROM AUTHOR]