King Grub
2016-04-03, 18:16
We have previously showed that performing resistance exercise (RE) to volitional fatigue, regardless of load, results in similar increases in skeletal muscle mass, fibre size and strength. However, these studies were performed in RE-naïve trainees using unilateral leg exercises. Here we aimed to determine whether the same was true in resistance trained (RT) young men using a whole-body RE regimen. We also aimed to address if there were any associations between post-RE systemic hormone concentrations with changes in skeletal muscle hypertrophy and strength. Forty-nine RT men (mean ± SEM, 23 ± 1 y, 86 ± 2 kg, 181 ± 1 cm) were randomly allocated into a high-repetition-low-load group (HR; 30-50% 1RM: 20-25 repetitions/set, n=24) or a low-repetition-high-load group (LR; 70-90% 1RM: 8-12 repetitions/set, n=25) and performed 12 wk of whole-body RE. Skeletal muscle biopsies, one repetition-maximums, dual-energy X-ray absorptiometry and blood draws in response to an acute bout of HR and LR were all evaluated pre- and post-intervention. Groups were matched at baseline for age, lean body mass, training experience, and strength for leg press, bench press, knee extension and shoulder press (p > 0.05). In response to the 12 wk intervention, muscular strength increased for all exercises in both groups (p <0.01), with change in bench press significantly greater in the LR group (HR; 9 ± 1, LR; 14 ±1 kg, p < 0.05). Lean body mass, type I and type II muscle fibre cross sectional area increased following training (p < 0.01) with no significant differences between groups and no change in fibre type distribution. All hormones (cortisol, free testosterone, total testosterone, dihydrotestosterone, dehydroepiandrosterone, luteinizing hormone, free insulin-like growth factor 1, total insulin-like growth factor 1 and growth hormone) increased as a result of an acute bout of RE (p < 0.001). Bivariate correlations revealed that no hormone at any time point was significantly correlated with the change in hypertrophy or strength. A stepwise multiple linear regression model revealed that three hormones accounted for a significant proportion of variance related to the intervention-induced change in hypertrophy or strength. Pre-intervention, the post-RE AUC for free insulin-like growth factor 1 and cortisol explained 15% and 12% of the change in leg press and type 2 cross sectional area, respectively. Post-intervention, the post-RE AUC of cortisol explained 9% of the change in type 2 CSA. These data show that when RE is performed to volitional fatigue neither repetition-load nor post-RE systemic hormone concentrations are significant determinants of gains in strength or hypertrophy in RT individuals.
The Biomedical Basis of Elite Performance 2016 (London, UK) (2016) Proc Physiol Soc 35, C04. Repetition-load and systemic hormone concentrations do not determine resistance training-mediated adaptations in trained young men.
The Biomedical Basis of Elite Performance 2016 (London, UK) (2016) Proc Physiol Soc 35, C04. Repetition-load and systemic hormone concentrations do not determine resistance training-mediated adaptations in trained young men.