Skeletal muscle adaptations to high‐intensity, low‐volume concurrent resistance and interval training in recreationally active men and women

Abstract

This study compared the structural and cellular skeletal muscle factors underpinning adaptations in maximal strength, power, aerobic capacity, and lean body mass to a 12‐week concurrent resistance and interval training program in men and women. Recreationally active women and men completed three training sessions per week consisting of high‐intensity, low‐volume resistance training followed by interval training performed using a variety upper and lower body exercises representative of military occupational tasks. Pre‐ and post‐training vastus lateralis muscle biopsies were analyzed for changes in muscle fiber type, cross‐sectional area, capillarization, and mitochondrial biogenesis marker content. Changes in maximal strength, aerobic capacity, and lean body mass (LBM) were also assessed. Training elicited hypertrophy of type I (12.9%; p = 0.016) and type IIa (12.7%; p = 0.007) muscle fibers in men only. In both sexes, training decreased type IIx fiber expression (1.9%; p = 0.046) and increased total PGC‐1α (29.7%, p < 0.001) and citrate synthase (11.0%; p < 0.014) content, but had no effect on COX IV content or muscle capillarization. In both sexes, training increased maximal strength and LBM but not aerobic capacity. The concurrent training program was effective at increasing strength and LBM but not at improving aerobic capacity or skeletal muscle adaptations underpinning aerobic performance.

Circulating extracellular vesicle characteristics differ between men and women following 12 weeks of concurrent exercise training

“…Importantly, while strength and lean body mass improved during this training program, maximal oxygen consumption did not, suggesting the acute exercise EV increase in trained men was not driven by improved aerobic capacity. The potential explanations for the lack of improvement in aerobic capacity during this concurrent training program have been discussed recently (Sterczala et al, 2024), with the likelihood that the interval intensity was not great enough to elicit strong increases in maximal oxygen consumption despite improvements in endurance performance tests (Sterczala et al, 2023). To interrogate whether the increase in circulating EV abundance following AHRET in trained men was exercise load related we evaluated the absolute and relative intensities of the baseline and 12-week AHRET bouts.…”