Abstract
We reported, using a unilateral resistance training (RT) model, that training with high or low loads (mass per repetition) resulted in similar muscle hypertrophy and strength improvements in RT-naïve subjects. Here we aimed to determine whether the same was true in men with previous RT experience using a whole-body RT program and whether postexercise systemic hormone concentrations were related to changes in hypertrophy and strength. Forty-nine resistance-trained men (23 ± 1 yr, mean ± SE) performed 12 wk of whole-body RT. Subjects were randomly allocated into a higher-repetition (HR) group who lifted loads of ∼30-50% of their maximal strength (1RM) for 20-25 repetitions/set (n = 24) or a lower-repetition (LR) group (∼75-90% 1RM, 8-12 repetitions/set, n = 25), with all sets being performed to volitional failure. Skeletal muscle biopsies, strength testing, dual-energy X-ray absorptiometry scans, and acute changes in systemic hormone concentrations were examined pretraining and posttraining. In response to RT, 1RM strength increased for all exercises in both groups (P < 0.01), with only the change in bench press being significantly different between groups (HR, 9 ± 1, vs. LR, 14 ± 1 kg, P = 0.012). Fat- and bone-free (lean) body mass and type I and type II muscle fiber cross-sectional area increased following training (P < 0.01) with no significant differences between groups. No significant correlations between the acute postexercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found. In congruence with our previous work, acute postexercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength. Our data show that in resistance-trained individuals, load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.
Highlights
We provide novel evidence of the effect of lifting markedly different loads during whole-body resistance training on the development of muscle strength and hypertrophy in previously trained persons
Recognizing the high interindividual response variability in hypertrophy and strength gain that occurs with RESISTANCE TRAINING (RT) [13, 27, 28, 48], we conducted the study with a large enough number of participants to allow detection of a 15% difference in hypertrophy via muscle fiber cross-sectional area (CSA) change and a 10% difference in fat- and bone-free body mass change measured by dual-energy X-ray absorptiometry (DXA) with 90% power based on previous work in trained men [33]
Higher- and lower-load per repetition RT programs were effective at inducing skeletal muscle hypertrophy in resistance-trained participants when RT was performed to volitional failure
Summary
We provide novel evidence of the effect of lifting markedly different (lighter vs. heavier) loads (mass per repetition) during whole-body resistance training on the development of muscle strength and hypertrophy in previously trained persons. Current recommendations are that RT with relatively heavy [i.e., at ϳ70 – 85% one-repetition maximum (1RM)] loads (“load” referring to the amount of mass used per repetition) is a prerequisite for maximizing RT-induced hypertrophy [12, 31] It has even been suggested, on the basis of only acute electromyography (EMG) data [despite caution on use of EMG in this manner [10]], that greater motor unit recruitment occurs when lifting heavier loads even if heavier and lighter loads are performed to volitional failure [16, 21]. In contrast to what others have proposed [18, 19, 31], we have demonstrated that resistance exercise-induced increases in circulating hormones play little role in regulating muscle protein synthesis after an acute bout of resistance exercise [51] or skeletal muscle hypertrophy following RT [50]. Our hypothesis was that neither load nor the acute postexercise increase in systemic hormones would determine RT-induced adaptations
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