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Knut Sindre Mølmen,* Sjur Johansen Øfsteng,* Bent R Rønnestad Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, Norway*These authors contributed equally to this workCorrespondence: Sjur Johansen ØfstengSection for Health and Exercise Physiology, Inland Norway University of Applied Sciences, Postbox 400, Elverum 2418, NorwayEmail sjur.johansen.ofsteng@inn.noBackground: Block periodization (BP) has been proposed as an alternative to traditional (TRAD) organization of the annual training plan for endurance athletes.Objective: To our knowledge, this is the first meta-analysis to evaluate the effect BP of endurance training on endurance performance and factors determinative for endurance performance in trained- to well-trained athletes.Methods: The PubMed, SPORTdiscus and Web of Science databases were searched from inception to August 2019. Studies were included if the following criteria were met: 1) the study examined a block-periodized endurance training intervention; 2) the study had a one-, two or multiple group-, crossover- or case-study design; 3) the study assessed at least one key endurance variable before and after the intervention period. A total of 2905 studies were screened, where 20 records met the eligibility criteria. Methodological quality for each study was assessed using the PEDro scale. Six studies were pooled to perform meta-analysis for maximal oxygen uptake (VO2max) and maximal power output (Wmax) during an incremental exercise test to exhaustion. Due to a lower number of studies and heterogenous measurements, other performance measures were systematically reviewed.Results: The meta-analyses revealed small favorable effects for BP compared to TRAD regarding changes in VO2max (standardized mean difference, 0.40; 95% CI=0.02, 0.79) and Wmax (standardized mean difference, 0.28; 95% CI=0.01, 0.54). For changes in endurance performance and workload at different exercise thresholds BP generally revealed moderate- to large-effect sizes compared to TRAD.Conclusion: BP is an adequate, alternative training strategy to TRAD as evidenced by superior training effects on VO2max and Wmax in athletes. The reviewed studies show promising effects for BP of endurance training; however, these results must be considered with some caution due to small studies with generally low methodological quality (mean PEDro score =3.7/10).Keywords: block training, traditional training, high-intensity training

The purpose of this study was to evaluate the effects of a microcycle of high-intensity interval training (HIT) sessions with multiple short work intervals followed by an active recovery period, compared to a similar duration of regular training, on determinants and indicators of endurance performance in well-trained cyclists. The participants in the BLOCK group performed a 6-day HIT microcycle including five HIT sessions (5 × 8.75-min 30/15 s short intervals) followed by a 6-day active recovery period with reduced training load, while the regular training group (REG) performed 12 days of their regular training, including four HIT sessions. Physiological testing was performed before and after the training periods. From pre- to post- intervention, BLOCK demonstrated significantly larger improvements than REG in mean power output (PO) during the last min of the maximal oxygen uptake (VO 2max ) test (PO VO2max ) (3.7 vs. 0.7%, p = 0.009, and effect size (ES) = 1.00) and mean PO during the 10-s sprint (2.8 vs. 1.9%, p = 0.028, and ES = 0.63). No significant differences between BLOCK and REG were observed for VO 2max , PO at 4 mmol·L -1 [blood lactate] (PO 4mmol ), 15-min maximal mean power output (PO 15-min ), and gross efficiency (p = 0.156-0.919). However, there was a tendency for larger improvements in the performance index (calculated from the main performance indicators PO VO2max , PO 4mmol , and PO 15-min ) in BLOCK compared to REG (2.9% vs. 1.2%, p = 0.079, and ES = 0.71). A 6-day high-intensity short-interval microcycle followed by a 6-day active recovery period induces improvements in endurance performance indicators compared to regular training, demonstrating its potential as an efficient strategy for endurance training in well-trained cyclists., (© 2024 The Author(s). European Journal of Sport Science published by Wiley‐VCH GmbH on behalf of European College of Sport Science.)

Background: Skeletal muscle mitochondria and capillaries are crucial for aerobic fitness, and suppressed levels are associated with chronic and age-related diseases. Currently, evidence-based exercise training recommendations to enhance these characteristics are limited. It is essential to explore how factors, such as fitness level, age, sex, and disease affect mitochondrial and capillary adaptations to different exercise stimuli., Objectives: The main aim of this study was to compare the effects of low- or moderate intensity continuous endurance training (ET), high-intensity interval or continuous training (HIT), and sprint interval training (SIT) on changes in skeletal muscle mitochondrial content and capillarization. Secondarily, the effects on maximal oxygen consumption (VO 2 max), muscle fiber cross-sectional area, and fiber type proportion were investigated., Methods: A systematic literature search was conducted in PubMed, Web of Science, and SPORTDiscus databases, with no data restrictions, up to 2 February 2022. Exercise training intervention studies of ET, HIT, and SIT were included if they had baseline and follow-up measures of at least one marker of mitochondrial content or capillarization. In total, data from 5973 participants in 353 and 131 research articles were included for the mitochondrial and capillary quantitative synthesis of this review, respectively. Additionally, measures of VO 2 max, muscle fiber cross-sectional area, and fiber type proportion were extracted from these studies., Results: After adjusting for relevant covariates, such as training frequency, number of intervention weeks, and initial fitness level, percentage increases in mitochondrial content in response to exercise training increased to a similar extent with ET (23 ± 5%), HIT (27 ± 5%), and SIT (27 ± 7%) (P > 0.138), and were not influenced by age, sex, menopause, disease, or the amount of muscle mass engaged. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in mitochondrial content. Per total hour of exercise, SIT was ~ 2.3 times more efficient in increasing mitochondrial content than HIT and ~ 3.9 times more efficient than ET, while HIT was ~ 1.7 times more efficient than ET. Capillaries per fiber increased similarly with ET (15 ± 3%), HIT (13 ± 4%) and SIT (10 ± 11%) (P = 0.556) after adjustments for number of intervention weeks and initial fitness level. Capillaries per mm 2 only increased after ET (13 ± 3%) and HIT (7 ± 4%), with increases being larger after ET compared with HIT and SIT (P < 0.05). This difference coincided with increases in fiber cross-sectional area after ET (6.5 ± 3.5%), HIT (8.9 ± 4.9%), and SIT (11.9 ± 15.1%). Gains in capillarization occurred primarily in the early stages of training (< 4 weeks) and were only observed in untrained to moderately trained participants. The proportion of type I muscle fibers remained unaltered by exercise training (P > 0.116), but ET and SIT exhibited opposing effects (P = 0.041). VO 2 max increased similarly with ET, HIT, and SIT, although HIT showed a tendency for greater improvement compared with both ET and SIT (P = 0.082), while SIT displayed the largest increase per hour of exercise. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in VO 2 max. Women displayed greater percentage gains in VO 2 max compared with men (P = 0.008). Generally, lower initial fitness levels were associated with greater percentage improvements in mitochondrial content, capillarization, and VO 2 max. SIT was particularly effective in improving mitochondrial content and VO 2 max in the early stages of training, while ET and HIT showed slower but steady improvements over a greater number of training weeks., Conclusions: The magnitude of change in mitochondrial content, capillarization, and VO 2 max to exercise training is largely determined by the initial fitness level, with greater changes observed in individuals with lower initial fitness. The ability to adapt to exercise training is maintained throughout life, irrespective of sex and presence of disease. While training load (volume × intensity) is a suitable predictor of changes in mitochondrial content and VO 2 max, this relationship is less clear for capillary adaptations., Competing Interests: Declarations. Funding: No funding was received for this work. Conflict of interest: Knut Sindre Mølmen, Nicki Winfield Almquist, and Øyvind Skattebo declare that they have no conflicts of interest relevant to the content of this review. Ethics approval: Not applicable. Consent to participate: Not applicable. Consent for publication: Not applicable. Availability of data and material: The dataset, statistical analysis codes, and SAS scripts are available from the study’s GitHub repository. To request access, please contact the corresponding author with your GitHub username, and access will be granted upon reasonable request. Authors contribution: K.S.M. and Ø.S. conceived and designed the study, with input from N.W.A.; K.S.M. conducted the literature search and initial study selection; K.S.M. and N.W.A. performed research article screening and data extraction; Ø.S. did the statistical analyses and data visualization; K.S.M., N.W.A., and Ø.S. contributed to the interpretation of the findings; K.S.M. and Ø.S. wrote the first draft of the manuscript; All authors provided critical revision, feedback, comments, and input on the manuscript. All authors read and approved the final manuscript., (© 2024. The Author(s).)

Purpose: Altitude training is a common strategy used with the intent to increase hemoglobin mass (Hb mass ) in athletes. However, if the Hb mass 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 Hb mass 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 Hb mass of 4.1%. Afterward, HEAT maintained Hb mass (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 Hb mass in elite cyclists after an altitude camp., (Copyright © 2024 by the American College of Sports Medicine.)

It has been suggested that time spent at a high fraction of maximal oxygen consumption (% V ˙ $\dot{\mathrm{V}}$ O 2max ) plays a decisive role for adaptations to interval training. However, previous studies examining how interval sessions should be designed to achieve a high % V ˙ $\dot{\mathrm{V}}$ O 2max have exclusively been performed in males. The present study compared the % V ˙ $\dot{\mathrm{V}}$ O 2max attained during three different 6 × 8 min interval protocols, in female (n = 11; V ˙ $\dot{\mathrm{V}}$ O 2max , 62.5 (6.4) mL · min -1 ·kg -1 ) and male (n = 8; V ˙ $\dot{\mathrm{V}}$ O 2max , 81.0 (5.2) mL · min -1 ·kg -1 ) cyclists. Mean power output during work intervals were identical across the three interval protocols, corresponding to the cyclist's 40 min maximal effort (PO 40min ): (1) 30 s intervals at 118% of PO 40min interspersed with 15 s active recovery at 60% (30/15), (2) constant pace at 100% of PO 40min (CON), and (3) altering between 60 s intervals at 110% and 60 s at 90% of PO 40min (60/60). Additionally, the study explored whether the m. vastus lateralis characteristics of the cyclists (fiber type proportion, capillarization, and citrate synthase activity) were associated with the % V ˙ $\dot{\mathrm{V}}$ O 2max attained during the interval sessions. Overall, mean % V ˙ $\dot{\mathrm{V}}$ O 2max and time ≥90% of V ˙ $\dot{\mathrm{V}}$ O 2max were higher during 30/15 compared to CON (86.7 (10.1)% and 1123 (787) s versus 85.0 (10.4)% and 879 (779) s, respectively; both p ≤ 0.01) and 60/60 (85.6 (10.0)% and 917 (745) s, respectively; both p ≤ 0.05), while no difference was observed between 60/60 and CON (both p ≥ 0.36). During interval sessions, % V ˙ $\dot{\mathrm{V}}$ O 2max and time ≥90% of V ˙ $\dot{\mathrm{V}}$ O 2max did not differ between sexes. Skeletal muscle characteristics were not related to % V ˙ $\dot{\mathrm{V}}$ O 2max  during interval sessions. In conclusion, well-trained cyclists demonstrate highest % V ˙ $\dot{\mathrm{V}}$ O 2max during 30/15, irrespective of sex and skeletal muscle characteristics., (© 2024 The Author(s). European Journal of Sport Science published by Wiley‐VCH GmbH on behalf of European College of Sport Science.)

It has been suggested that time at a high fraction (%) of maximal oxygen uptake (VO 2max ) plays a decisive role for adaptations to interval training. Yet, no study has, to date, measured the % of VO 2max during all interval sessions throughout a prolonged training intervention and subsequently related it to the magnitude of training adaptations. Thus, the present study aimed to investigate the relationship between % of VO 2max achieved during an interval training intervention and changes in endurance performance and its physiological determinants in well-trained cyclists. Twenty-two cyclists (VO 2max 67.1 (6.4) mL·min -1  ·kg -1 ; males, n = 19; females, n = 3) underwent a 9-week interval training intervention, consisting 21 sessions of 5 × 8-min intervals conducted at their 40-min highest sustainable mean power output (PO). Oxygen uptake was measured during all interval sessions, and the relationship between % of VO 2max during work intervals and training adaptations were investigated using linear regression. A performance index was calculated from several performance measures. With higher % of VO 2max during work intervals, greater improvements were observed for maximal PO during the VO 2max test (R 2 adjusted  = 0.44, p = 0.009), PO at 4 mmol·L -1 [blood lactate] (R 2 adjusted  = 0.25, p = 0.035), the performance index (R 2 adjusted  = 0.36, p = 0.013), and VO 2max (R 2 adjusted  = 0.54, p = 0.029). Other measures, such as % of maximal heart rate, were related to fewer outcome variables and exhibited poorer session-to-session repeatability compared to % of VO 2max . In conclusion, improvements in endurance measures were positively related to the % of VO 2max achieved during interval training. Percentage of VO 2max was the measure that best reflected the magnitude of training adaptations., (© 2024 The Author(s). European Journal of Sport Science published by Wiley‐VCH GmbH on behalf of European College of Sport Science.)

Altitude training is a cornerstone for endurance athletes for improving blood variables and performance, with optimal effects observed at ∼2,300-2,500 meters above sea level (m.a.s.l.). However, elite cyclists face challenges such as limited access to such altitudes, inadequate training facilities, and high expenses. To address these issues, a novel method involving daily exposure to carbon monoxide (CO) has been proposed to amplify altitude training adaptations at suboptimal altitudes. Thirty-one male cyclists were assigned to three groups: Live-High Train-High with CO inhalation (LHTH CO ), Live-High Train-High (LHTH), and Live-Low Train-Low (LLTL). The LHTH CO group underwent CO inhalation twice daily in the afternoon/evening to elevate carboxyhemoglobin concentration to ∼10%. Hematological variables, in vivo muscle oxidative capacity, and physiological indicators of cycling performance were assessed before and after a 3-week altitude training camp at 2,100 m.a.s.l. LHTH CO demonstrated a larger increase in hemoglobin mass (Hb mass ) compared to both LHTH and LLTL. Although there were no statistical differences between LHTH CO and LHTH in submaximal and maximal performance measures, LHTH CO displayed greater improvements in 1-min maximal power output during incremental testing (W max ), power output at lactate threshold, and maximal oxygen consumption (V̇o 2max ) compared to LLTL. LHTH demonstrated a larger improvement than LLTL in W max and V̇o 2max , with no group differences in Hb mass or submaximal measures. Muscle oxidative capacity did not differ between groups. These findings suggest that combining moderate-altitude training with daily CO inhalation promotes hematological adaptations more effectively than moderate altitude alone and enhances cycling performance metrics in cyclists more than sea-level training. NEW & NOTEWORTHY Three weeks of training at moderate altitude with exposure to low doses of CO can significantly enhance hematological adaptations in elite cyclists compared to moderate-altitude training alone. Cycling performance determinants improved more with CO inhalation at moderate altitude compared to sea-level training, whereas there were no differences in submaximal and maximal performance measures compared to moderate-altitude training alone. This study highlights the potential of CO supplementation as an effective adjunct to altitude training regimens.

Purpose: Resistance training-induced skeletal muscle hypertrophy seems to depend on ribosome biogenesis and content. High glucose treatment may augment ribosome biogenesis through potentiating resistance training-induced adaptations. This was investigated with total RNA and ribosomal RNA abundances as main outcomes, with relevant transcriptional/translational regulators (c-Myc/UBF/rpS6) as a secondary outcome., Methods: Sixteen healthy, moderately trained individuals [male/female, n = 9/7; age, 24.1 (3.3)] participated in a within-participant crossover trial with unilateral resistance training (leg press and knee extension, 3 sets of 10 repetitions maximum) and pre- and post-exercise ingestion of either glucose (3 × 30 g, 90 g total) or placebo supplements (Stevia rebaudiana, 3 × 0.3 g, 0.9 g total), together with protein (2 × 25 g, 50 g total), on alternating days for 12 days. Six morning resistance exercise sessions were conducted per condition, and the sessions were performed in an otherwise fasted state. Micro-biopsies were sampled from m. vastus lateralis before and after the intervention., Results: Glucose ingestion did not have beneficial effects on resistance training-induced increases of ribosomal content (mean difference 7.6% [- 7.2, 24.9], p = 0.34; ribosomal RNA, 47S/18S/28S/5.8S/5S, range 7.6-37.9%, p = 0.40-0.98) or levels of relevant transcriptional or translational regulators (c-MYK/UBF/rpS6, p = 0.094-0.292). Of note, both baseline and trained state data of total RNA showed a linear relationship with UBF; a ∼14% increase in total RNA corresponded to 1 SD unit increase in UBF (p = 0.003)., Conclusion: Glucose ingestion before and after resistance training sessions did not augment ribosomal RNA accumulation during twelve days of heavy-load resistance training in moderately trained young adults., (© 2024. The Author(s).)

Interval training is considered an essential training component in endurance athletes. Recently, there has been a focus on optimization of interval training characteristics to sustain a high fraction of maximal oxygen consumption (≥90% VO 2max ) to improve physiological adaptations and performance. Herein, we present a synopsis of the latest research exploring both acute and chronic studies in endurance athletes. Further, a decision flowchart was created for athletes and coaches to select the most appropriate interval training regime for specific individualized goals., Competing Interests: The authors declare that they have no conflicts of interest relevant to the content of this article.

Background: Changes in tryptophan metabolism through the kynurenine pathway (KP) are observed in several disorders and coupled with pathophysiological deviations., Methods: This study retrospectively compared the KP in serum in healthy subjects (108) with subjects with obesity (141), depression (49), and chronic obstructive pulmonary disease (COPD) (22) participating in four clinical studies and explored predictors of the changes in the KP metabolites., Results: Compared with the healthy group, the KP was upregulated in the disease groups with high kynurenine, quinolinic acid (QA), kynurenine/tryptophan-ratio and QA/xanthurenic acid-ratio and low kynurenic acid/QA-ratio. Tryptophan and xanthurenic acid were upregulated in the depressed group compared with the groups with obesity and COPD. The covariates BMI, smoking, diabetes, and C-reactive protein explained the significant differences between the healthy group and the group with obesity but not between the healthy group and the groups with depression and COPD, indicating that different pathophysiological conditions result in the same changes in the KP., Conclusions: The KP was significantly upregulated in the disease groups compared with the healthy group, and there were significant differences between the disease groups. Different pathophysiological abnormalities seemed to result in the same deviations in the KP.

Purpose: The aim of this study was to compare the effects of a 6-day high-intensity interval (HIT) block [BLOCK, n = 12, maximal oxygen uptake (V̇O 2max = 69. 6 ± 4.3 mL·min -1 ·kg -1 )] with a time-matched period with usual training (CON, n = 12, V̇O 2max = 69.2 ± 4.2 mL·min -1 ·kg -1 ) in well-trained cross-country (XC) skiers on physiological determinants and indicators of endurance performance. Furthermore, the study aimed to investigate the acute physiological responses, including time ≥90% of V̇O 2max , and its associated reliability during repeated HIT sessions in the HIT microcycle., Methods: Before the 6-day HIT block and following 5 days of recovery after the HIT block, both groups were tested on indicators of endurance performance. To quantify time ≥90% of V̇O 2max during interval sessions in the HIT block, V̇O 2 measurements were performed on the 1st, 2nd, and last HIT session in BLOCK., Results: BLOCK had a larger improvement than CON in maximal 1-min velocity achieved during the V̇O 2max test (3.1 ± 3.1% vs. 1.2 ± 1.6%, respectively; p = 0.010) and velocity corresponding to 4 mmol·L -1 blood lactate (3.2 ± 2.9% vs. 0.6 ± 2.1%, respectively; p = 0.024). During submaximal exercise, BLOCK displayed a larger reduction in respiratory exchange ratio, blood lactate concentration, heart rate, and rate of perceived exertion ( p < 0.05) and a tendency towards less energy expenditure compared to CON ( p = 0.073). The ICC of time ≥90% V̇O 2max in the present study was 0.57, which indicates moderate reliability., Conclusions: In well-trained XC skiers, BLOCK induced superior changes in indicators of endurance performance compared with CON, while time ≥90% of V̇O 2max during the HIT sessions in the 6-day block had a moderate reliability., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Rønnestad, Bjerkrheim, Hansen and Mølmen.)

Purpose: The primary purpose was to test the effect of heat suit training on hemoglobin mass (Hb mass ) in elite cross-country (XC) skiers., Methods: Twenty-five male XC-skiers were divided into a group that added 5 × 50 min weekly heat suit training sessions to their regular training (HEAT; n = 13, 23 ± 5 years, 73.9 ± 5.2 kg, 180 ± 6 cm, 76.8 ± 4.6 ml·min -1 ·kg -1 ) or to a control group matched for training volume and intensity distribution (CON; n = 12, 23 ± 4 years, 78.4 ± 5.8 kg, 184 ± 4 cm, 75.2 ± 3.4 ml·min -1 ·kg -1 ) during the five-week intervention period. Hb mass , endurance performance and factors determining endurance performance were assessed before and after the intervention., Results: HEAT led to 30 g greater Hb mass (95% CI: [8.5, 51.7], p = 0.009) and 157 ml greater red blood cell volume ([29, 285], p = 0.018) post-intervention, compared to CON when adjusted for baseline values. In contrast, no group differences were observed for changes in work economy, running velocity, and fractional utilization of maximal oxygen uptake (V̇O 2max ) at 4 mmol·L -1 blood lactate, V̇O 2max or 15-min running distance performance trial during the intervention., Conclusion: HEAT induced a larger increase in Hb mass and red blood cell volume after five weeks with five weekly heat suit training sessions than CON, but with no detectable group differences on physiological determinants of endurance performance or actual endurance performance in elite CX skiers., (© 2022 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Background: Subjects with chronic obstructive pulmonary disease (COPD) are prone to accelerated decay of muscle strength and mass with advancing age. This is believed to be driven by disease-inherent systemic pathophysiologies, which are also assumed to drive muscle cells into a state of anabolic resistance, leading to impaired abilities to adapt to resistance exercise training. Currently, this phenomenon remains largely unstudied. In this study, we aimed to investigate the assumed negative effects of COPD for health- and muscle-related responsiveness to resistance training using a healthy control-based translational approach., Methods: Subjects with COPD (n = 20, GOLD II-III, FEV 1predicted 57 ± 11%, age 69 ± 5) and healthy controls (Healthy, n = 58, FEV 1predicted 112 ± 16%, age 67 ± 4) conducted identical whole-body resistance training interventions for 13 weeks, consisting of two weekly supervised training sessions. Leg exercises were performed unilaterally, with one leg conducting high-load training (10RM) and the contralateral leg conducting low-load training (30RM). Measurements included muscle strength (n variables  = 7), endurance performance (n variables  = 6), muscle mass (n variables  = 3), muscle quality, muscle biology (m. vastus lateralis; muscle fiber characteristics, RNA content including transcriptome) and health variables (body composition, blood). For core outcome domains, weighted combined factors were calculated from the range of singular assessments., Results: COPD displayed well-known pathophysiologies at baseline, including elevated levels of systemic low-grade inflammation ([c-reactive protein] serum ), reduced muscle mass and functionality, and muscle biological aberrancies. Despite this, resistance training led to improved lower-limb muscle strength (15 ± 8%), muscle mass (7 ± 5%), muscle quality (8 ± 8%) and lower-limb/whole-body endurance performance (26 ± 12%/8 ± 9%) in COPD, resembling or exceeding responses in Healthy, measured in both relative and numeric change terms. Within the COPD cluster, lower FEV 1predicted was associated with larger numeric and relative increases in muscle mass and superior relative improvements in maximal muscle strength. This was accompanied by similar changes in hallmarks of muscle biology such as rRNA-content↑, muscle fiber cross-sectional area↑, type IIX proportions↓, and changes in mRNA transcriptomics. Neither of the core outcome domains were differentially affected by resistance training load., Conclusions: COPD showed hitherto largely unrecognized responsiveness to resistance training, rejecting the notion of disease-related impairments and rather advocating such training as a potent measure to relieve pathophysiologies., Trial Registration: ClinicalTrials.gov ID: NCT02598830. Registered November 6th 2015, https://clinicaltrials.gov/ct2/show/NCT02598830.

Background: Lifestyle therapy with resistance training is a potent measure to counteract age-related loss in muscle strength and mass. Unfortunately, many individuals fail to respond in the expected manner. This phenomenon is particularly common among older adults and those with chronic diseases (e.g. chronic obstructive pulmonary disease, COPD) and may involve endocrine variables such as vitamin D. At present, the effects of vitamin D supplementation on responses to resistance training remain largely unexplored., Methods: Ninety-five male and female participants (healthy, n = 71; COPD, n = 24; age 68 ± 5 years) were randomly assigned to receive either vitamin D 3 or placebo supplementation for 28 weeks in a double-blinded manner (latitude 61°N, September-May). Seventy-eight participants completed the RCT, which was initiated by 12 weeks of supplementation-only (two weeks with 10 000 IU/day, followed by 2000 IU/day), followed by 13 weeks of combined supplementation (2000 IU/day) and supervised whole-body resistance training (twice weekly), interspersed with testing and measurements. Outcome measures included multiple assessments of muscle strength (n variables  = 7), endurance performance (n = 6), and muscle mass (n = 3, legs, primary), as well as muscle quality (legs), muscle biology (m. vastus lateralis; muscle fibre characteristics, transcriptome), and health-related variables (e.g. visceral fat mass and blood lipid profile). For main outcome domains such as muscle strength and muscle mass, weighted combined factors were calculated from the range of singular assessments., Results: Overall, 13 weeks of resistance training increased muscle strength (13% ± 8%), muscle mass (9% ± 8%), and endurance performance (one-legged, 23% ± 15%; whole-body, 8% ± 7%), assessed as weighted combined factors, and were associated with changes in health variables (e.g. visceral fat, -6% ± 21%; [LDL] serum , -4% ± 14%) and muscle tissue characteristics such as fibre type proportions (e.g. IIX, -3% points), myonuclei per fibre (30% ± 65%), total RNA/rRNA abundances (15%/6-19%), and transcriptome profiles (e.g. 312 differentially expressed genes). Vitamin D 3 supplementation did not affect training-associated changes for any of the main outcome domains, despite robust increases in [25(OH)D] serum (∆49% vs. placebo). No conditional effects were observed for COPD vs. healthy or pre-RCT [25(OH)D] serum . In secondary analyses, vitamin D 3 affected expression of gene sets involved in vascular functions in muscle tissue and strength gains in participants with high fat mass, which advocates further study., Conclusions: Vitamin D 3 supplementation did not affect muscular responses to resistance training in older adults with or without COPD., (© 2021 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of Society on Sarcopenia, Cachexia and Wasting Disorders.)