Resistance exercise training is the most effective and accepted strategy for increasing skeletal muscle mass and strength. There is tremendous individual variability in the adaptive response to exercise and the source(s) contributing to this variability are largely unknown. Recent evidence in the literature supports the notion that capillaries may be a potential target for improving outcomes to chronic resistance exercise. Aerobic exercise training is a proven stimulus for eliciting angiogenesis and increasing capillary content. Therefore, we hypothesize that completing a period of aerobic training prior to resistance training will result in a greater increase in fibre cross sectional area (CSA) compared to resistance training alone. Fourteen participants (8M, 6F) completed 6 weeks of unilateral single leg aerobic training prior to undergoing 10 weeks of bilateral lower body resistance exercise training. Performance and anthropometric measures were completed at baseline, post aerobic training and post resistance training. Skeletal muscle biopsies were obtained from the vastus lateralis and immunofluorescent staining of muscle cross sections was completed to determine fibre CSA and satellite cell content. Following unilateral aerobic training, single leg VO2 work peak (Watts) (p<0.001), and oxygen consumption (O2 mL min-1) (p=.0033) was significantly higher in the aerobically trained limb (EX) versus the control (CTL) limb. Capillary to perimeter fibre exchange index (CFPE) (p<0.05), a measure of microvascular perfusion, was significantly higher in the EX versus CTL limb following unilateral aerobic training. Resistance training resulted in increases in 1-repetition maximum of both squat (p<0.0001) and leg press (p<0.0001). A main effect of time was observed for limb fat free mass (p<0.0001) as determined via DEXA. Type-II fibre CSA of the EX limb was greater (p<0.05) versus CTL limb following resistance exercise training. Type-II fibre associated satellite cell content of the CTL limb was elevated (p<0.01) following resistance training. Results suggest that a period of unilateral aerobic training elevates the aerobic capacity and relative microvascular perfusion of the trained leg significantly in comparison to the non-aerobically conditioned limb. Subsequent resistance training, bilateral leg strength increased post resistance training while type II CSA increased in the aerobically pre-conditioned limb following resistance training. Collectively, these results suggest that a period of aerobic preconditioning may augment the muscle’s ability to respond to a hypertrophic stimulus. / Thesis / Master of Science (MSc) / Resistance exercise training is the most effective and accepted strategy for increasing skeletal muscle mass and strength. Yet, there is tremendous individual variability in the adaptive response to exercise and the source(s) contributing to this variability are largely unknown. Recently, evidence has emerged suggesting that capillaries may be a potential target for enhancing the adaptive response to chronic resistance exercise training. Research has only begun to characterize the extent to which microvascular perfusion (capillarization and blood flow to the muscle) plays a role in muscle health and resistance training outcomes. Currently, it is unknown if elevating microvascular perfusion is enough to facilitate greater accretion (hypertrophy) of muscle mass and strength following resistance training. Therefore, the current study hypothesized that increased microvascular perfusion induced by a pre-conditioning period of aerobic training, lasting 6-weeks, would be sufficient to enhance muscle accretion (hypertrophy) and elevate muscle stem cell content following resistance exercise training. To examine this, a cohort of young men and women performed 6 weeks of unilateral (single-leg) cycling following by 10 weeks of bilateral (both legs) resistance exercise training. Results demonstrated an increased oxidative capacity and capillary perfusion in the aerobically-trained limb following single-leg cycling, as expected. Consistent with our initial hypothesis, we observed superior muscle hypertrophy of type-II muscle fibres (increased fibre cross-sectional area), in the aerobically-conditioned limb following resistance training. The results suggest that muscle capillarization may be a determinant and facilitator of adaptation to resistance training and its outcomes.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25065 |
| Date | January 2019 |
| Creators | Thomas, Aaron |
| Contributors | Parise, Gianni, Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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