Abstract
While high-load resistance training increases muscle hypertrophy, the intramuscular protein responses to this form of training remains largely unknown. In the current study, recreationally resistance-trained college-aged males (N = 15; mean ± SD: 23 ± 3 years old, 6 ± 5 years training) performed full-body, low-volume, high-load [68–90% of one repetition maximum (1RM)] resistance training over 10 weeks. Back squat strength testing, body composition testing, and a vastus lateralis biopsy were performed before (PRE) and 72 h after the 10-week training program (POST). Fiber type-specific cross-sectional area (fCSA), myofibrillar protein concentrations, sarcoplasmic protein concentrations, myosin heavy chain and actin protein abundances, and muscle tissue percent fluid were analyzed. The abundances of individual sarcoplasmic proteins in 10 of the 15 participants were also assessed using proteomics. Significant increases (p < 0.05) in type II fCSA and back squat strength occurred with training, although whole-body fat-free mass paradoxically decreased (p = 0.026). No changes in sarcoplasmic protein concentrations or muscle tissue percent fluid were observed. Myosin heavy chain protein abundance trended downward (−2.9 ± 5.8%, p = 0.069) and actin protein abundance decreased (−3.2 ± 5.3%, p = 0.034) with training. Proteomics indicated only 13 sarcoplasmic proteins were altered with training (12 up-regulated, 1 down-regulated, p < 0.05). Bioinformatics indicated no signaling pathways were affected, and proteins involved with metabolism (e.g., ATP-PCr, glycolysis, TCA cycle, or beta-oxidation) were not affected. These data comprehensively describe intramuscular protein adaptations that occur following 10 weeks of high-load resistance training. Although previous data from our laboratory suggests high-volume resistance training enhances the ATP-PCr and glycolytic pathways, we observed different changes in metabolism-related proteins in the current study with high-load training.
Highlights
MATERIALS AND METHODSHigh-load resistance exercise involves performing lifts with heavier weights for fewer repetitions [sets consisting of 1–6 repetitions at ≥75% one repetition maximum (1RM)]
Eligible participants had to be free of cardiometabolic diseases or conditions precluding the collection of a skeletal muscle biopsy
Our data suggest 10 weeks of high-load resistance training facilitates the following adaptations in these participants: (a) a robust increase in lower body strength, (b) a modest, but significant decrease in whole body fat-free mass (FFM), (c) a significant increase in type II, but not type I, fiber cross-sectional area (fCSA), (d) a modest, but significant, decrease in skeletal muscle actin protein abundance and a similar statistical trend with myosin heavy chain protein abundance, (e) no changes in muscle fluid content or sarcoplasmic protein concentrations, and (f) marginal alterations in the sarcoplasmic proteome, with only 13 proteins being altered from performed before (PRE) to POST (12 up, 1 down, unadjusted p < 0.05)
Summary
MATERIALS AND METHODSHigh-load resistance exercise involves performing lifts with heavier weights for fewer repetitions [sets consisting of 1–6 repetitions at ≥75% one repetition maximum (1RM)]. There has been recent enthusiasm surrounding molecular signaling events that occur in skeletal muscle in response to higher load versus moderate-to-higher volume resistance exercise (Burd et al, 2010; Haun et al, 2017; Morton et al, 2019). These studies have reported that acute anabolic signaling events do not differ between exercise modalities when lifts are performed to volitional fatigue. The intramuscular protein adaptations that occur in response to each mode of training – changes in myofibrillar protein concentrations, sarcoplasmic protein concentrations, or muscle tissue percent fluid – have been vastly understudied
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