Sex-based comparisons of muscle cellular adaptations after 10 weeks of progressive resistance training in middle-aged adults

Abstract

Resistance training combined with adequate protein intake supports skeletal muscle strength and hypertrophy. These adaptations are supported by the action of muscle stem cells (MuSCs) which are regulated, in part, by fibro-adipogenic progenitors (FAPs) and circulating factors delivered through capillaries. It is unclear if middle-aged males and females have similar adaptations to resistance training at the cellular level. To address this gap, 27 (13 males, 14 females) middle-aged (40-64 years) adults participated in 10-weeks of whole-body resistance training with dietary counselling. Muscle biopsies were collected from the vastus lateralis pre- and post-training. Type II fibre cross-sectional area increased similarly with training in both sexes (P = 0.014). MuSC content was not altered with training; however, training increased PDGFRα+/CD90+ FAP content (P < 0.0001) and reduced PDGFRα+/CD90- FAP content (P = 0.044), independent of sex. The number of CD31+ capillaries per fibre also increased similarly in both sexes (p<0.05). These results suggest that muscle fibre hypertrophy, stem/progenitor cell, and capillary adaptations are similar between middle-aged males and females in response to whole-body resistance training.

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

“…In contrast with the current study, past research has reported female muscle fiber hypertrophy resulting from resistance and concurrent training programs (Bell et al, 2000;Binet et al, 2023;Roberts et al, 2020;Spiliopoulou et al, 2021;Staron et al, 1990). Although sex-specific muscle fiber hypertrophy has been reported following resistance training interventions (Bamman et al, 2003;Martel et al, 2006;Moesgaard et al, 2022), a recent meta-analysis concluded that there is no difference in the hypertrophic response to resistance training between men and women (Roberts et al, 2020).…”

Sex-based differences in Muscle Stem Cell Regulation Following Exercise

“…Similarly, previous work has found that males had a greater MuSC content in type II fibers compared with females, with no differences in type I fibers (20,21). These findings are supported by work from our laboratory finding that showed a trend for more MuSCs in males compared to females (22). Contrastingly, several studies have found no sex effect on MuSC content (23)(24)(25).…”

“…Discrepancies in the existing literature could be further related to differences in age, habitual training status, small number of biological samples, and hormonal variations between participants. Additionally, it has been shown that males have a greater myonuclear content and a greater myonuclear domain compared to females (20,22). This is of importance as myonuclear content and larger myonuclear domains are positively correlated with MuSC content (29,30).…”

Influence of sexual dimorphism on satellite cell regulation and inflammatory response during skeletal muscle regeneration

“…Conflicting findings have been reported on the number of Pax7 + cells in men and women at steady state. While several studies showed no difference in SC number between men and women in the vastus lateralis and tibialis anterior muscles (Binet et al, 2023;Fortino et al, 2022;Kadi et al, 2004;Roth et al, 2000), other investigations reported that men had more Pax7 + SCs in type II myofibers as compared with women (Abou Sawan et al, 2021;Horwath et al, 2021). In vitro investigations showed similar proliferation and fusion rates between sexes in four different muscles (i.e., tensor fasciae, vastus lateralis and medialis and rectus femoris) (Bonavaud et al, 1997).…”