Short‐term aerobic conditioning prior to resistance training augments muscle hypertrophy and satellite cell content in healthy young men and women

Abstract

Factors influencing inter-individual variability of responses to resistance training(RT) remain to be fully elucidated. We have proposed the importance of capillarization in skeletal muscle for the satellite cell (SC) response to RT-induced muscle hypertrophy, and hypothesized that aerobic conditioning (AC) would augment RT-induced adaptations. Fourteen healthy young (22 ± 2 years) men and women underwent AC via 6 weeks of unilateral cycling followed by 10 weeks of bilateral RT to investigate how AC alters SC content, activity, and muscle hypertrophy following RT. Muscle biopsies were taken at baseline (unilateral), post AC (bilateral), and post RT (bilateral) in the aerobically conditioned (AC + RT) and unconditioned (RT) legs. Immunofluorescence was used to determine muscle capillarization, fiber size, SC content, and activity. Type I and type II fiber cross-sectional area (CSA) increased following RT, and when legs were analyzed independently, AC + RT increased type I, type II, and mixed-fiber CSA, where the RT leg tended to increase type II (p = .05), but not type I or mixed-fiber CSA. SC content, activation, and differentiation increased with RT, where type I total and quiescent SC content was greater in AC + RT compared to the RT leg. Those with the greatest capillary-to-fiber perimeter exchange index before RT had the greatest change in CSA following RT and a significant relationship was observed between type II fiber capillarization and the change in type II-fiber CSA with RT (r = 0.35). This study demonstrates that AC prior to RT can augment RT-induced muscle adaptions and that these differences are associated with increases in capillarization.

Aerobic conditioning alters the satellite cell and ribosome response to acute eccentric contractions in young men and women

“…Work in middle-aged women has also demonstrated that endurance training is able to alter the acute SC response to a bout of resistance exercise ( 39 ). The participants in the present study experienced an increase in V̇ o 2 peak and skeletal muscle capillarization following single-legged AC ( 28 ), which was associated with an augmented type-I SC content, further supporting the notion that training status and specifically capillary content can impact SC function.…”

“…Another study in sedentary middle-aged individuals that completed 12 wk of aerobic conditioning also reported an increase in type-I SC content, however, this was also accompanied by an increase in type-I fiber CSA ( 42 ). Although the participants in our study did not increase type-I CSA following aerobic conditioning ( 28 ), previous work by our laboratory has demonstrated an increase in activated SC following aerobic conditioning, which may act as an anticipatory response for future stimuli ( 34 ).…”

“…Participants underwent 6 weeks of single-legged aerobic conditioning on a randomized leg (Aerobically Conditioned, "AC") where the other acted as a non-conditioned control (CTL) (28). Participants underwent resting (Pre) skeletal muscle biopsies from the vastus lateralis of both the AC and CTL legs according to Tarnopolsky et al, (2011) at least 1 week following the last AC bout.…”

“…Baseline participant characteristics have previously been described by Thomas et al ( 28 ) and are summarized in Table 1 .…”

Resistance Training Diminishes Mitochondrial Adaptations to Subsequent Endurance Training

“…In addition, while several studies have investigated the effects of concurrent training, when both RT and ET are combined within the same training session or program, no study to date has employed a design that investigated RTonly followed by ET-only. This is especially relevant considering a recent study reported that prior ET facilitated adaptations to a subsequent period of RT (16).…”