Search

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 D3 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 (nvariables = 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 D3 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 D3 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 D3 supplementation did not affect muscular responses to resistance training in older adults with or without COPD. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?Do haemoglobin mass and red blood cell volume increase in elite cyclists training in a hot environment compared to a control group training at normal temperature?What is the main finding and its importance?Five weeks of heat training increases haemoglobin mass in elite cyclists. There are small to intermediate effect sizes for exercise parameters favouring heat training. In this study we tested the hypothesis that performing 1 h of regular light exercise in a heat chamber (HEAT; 37.8 ± 0.5°C; 65.4 ± 1.8% humidity) 5 times week−1 for a total of 5 weeks increases haemoglobin mass (Hbmass) and exercise performance in elite cyclists (V̇O2max = 76.2 ± 7.6 ml min−1 kg−1). Twenty‐three male volunteers were assigned to HEAT (n = 11) or CON (n = 12; 15.5 ± 0.1°C; 25.1 ± 0.0% humidity) training groups. Hbmass was determined before and after the intervention period in conjunction with an extensive exercise test protocol (conducted at 16–19°C). HEAT increased (P < 0.05) Hbmass by 42 g from 893 ± 78 to 935 ± 108 g whereas Hbmass remained unchanged (+6 g) in CON. Furthermore, statistical analysis revealed a time–group interaction (P < 0.05). The greater increase in Hbmass in HEAT, however, did not manifest in a greater increase in V̇O2max (225 ± 274 ml min−1 in HEAT and 161 ± 202 ml min−1 in CON). While HEAT reduced (P < 0.05) lactate levels during some of the submaximal exercise tests, there was no statistical difference between other performance parameters. There were, however, small to intermediate effect sizes favouring HEAT for lactate threshold power output (2.8 ± 3.9 vs. −0.4 ± 5.1% change, effect size (ES) = 0.34), gross economy in the fatigued state (0.19 ± 0.42 vs. −0.12 ± 0.49%‐point change, ES = 0.52) and 15 min mean power (6.9 ± 8.4 vs. 3.4 ± 5.1% increase, ES = 0.22). This study demonstrates an increase in Hbmass and small to intermediate effect sizes on exercise variables in elite cyclists following a 5‐week heat training intervention. [ABSTRACT FROM AUTHOR]

Blood volume (BV) is an important clinical parameter and is usually reported per kg of body mass (BM). When fat mass is elevated, this underestimates BV/BM. One aim was to study if differences in BV/BM related to sex, age, and fitness would decrease if normalized to lean body mass (LBM). The analysis included 263 women and 319 men (age: 10-93 years, body mass index: 14-41 kg/m 2 ) and 107 athletes who underwent assessment of BV and hemoglobin mass (Hb mass ), body composition, and cardiorespiratory fitness. BV/BM was 25% lower (70.3 ± 11.3 and 80.3 ± 10.8 mL/kg BM ) in women than men, respectively, whereas BV/LBM was 6% higher in women (110.9 ± 12.5 and 105.3 ± 11.2 mL/kg LBM ). Hb mass /BM was 34% lower (8.9 ± 1.4 and 11.5 ± 11.2 g/kg BM ) in women than in men, respectively, but only 6% lower (14.0 ± 1.5 and 14.9 ± 1.5 g/kg LBM )/LBM. Age did not affect BV. Athlete's BV/BM was 17.2% higher than non-athletes, but decreased to only 2.5% when normalized to LBM. Of the variables analyzed, LBM was the strongest predictor for BV (R 2  = .72, p < .001) and Hb mass (R 2  = .81, p < .001). These data may only be valid for BV/Hb mass when assessed by CO re-breathing. Hb mass /LBM could be considered a valuable clinical matrix in medical care aiming to normalize blood homeostasis., (© 2023 The Authors. American Journal of Hematology published by Wiley Periodicals LLC.)

Heat exercise training may increase exercise performance in athletes. The underlying mechanisms remain partly unresolved, and it is unknown if female and male athletes may experience comparable gains. The aims were to investigate whether heat training (HEAT) increases hemoglobin mass (Hb mass ), skeletal muscle fiber characteristics, and thermoneutral exercise performance in elite female and male endurance athletes. Female ( n = 20; V̇o 2max = 58.2 ± 6.7 mL·min -1 ·kg -1 ) and male ( n = 27; V̇o 2max = 76.4 ± 7.8 mL·min -1 ·kg -1 ) cyclists were studied before and after 5 wk of randomized control or HEAT consisting of five weekly sessions each of 50 min duration, which were included in their normal training regimes. Overall, the observed relative responses to HEAT were largely similar in female and male study participants. HEAT increased ( P < 0.05) Hb mass in females from 650 ± 77 to 675 ± 76 g (4.0 ± 1.6%) and from 1,008 ± 155 to 1,041 ± 147 g (3.5 ± 2.3%) in males. In contrast, skeletal muscle citrate synthase activity, fiber type distribution, and capillary density remained unchanged with HEAT. Lactate threshold, V̇o 2max , and mean power output during 15-min all-out testing were all enhanced ( P < 0.05) following HEAT in female and male study participants. In conclusion, 5 wk of HEAT increases Hb mass in female and male elite cyclists and improves exercise performance in a thermoneutral environment. Based on this, heat training may be recommended to elite female and male athletes aiming to perform in a thermoneutral environment. NEW & NOTEWORTHY We demonstrate in elite female and male cyclists that heat exercise training (5 × 50 min sessions/wk for 5 wk) facilities Hb mass and other hematological parameters more than control exercise training, whereas skeletal muscle properties remain unaltered. Collectively, this coincided with improvements in lactate threshold, V̇o 2max , and 15-min all-out cycling performance.