Skeletal Muscle Growth Responses to Voluminous Resistance Training in Young Men with or without Graded Dosage of Protein Supplementation

Abstract

Purpose: We examined hypertrophic outcomes of weekly graded whey protein dosing (GWP) versus whey protein (WP) or maltodextrin (MALTO) dosed once daily during 6 weeks of resistance training (RT). Methods: College-aged resistance-trained males (training age=5±1 yrs; mean±SE) were assigned to WP (25g/d; n=10), MALTO (30g/d; n=10), or GWP (25-150 g/d from weeks 1-6; n=11). RT occurred 3d/wk (2 upper- and 2 lower-body exercises/d, 10 repetitions/set), and RT volume increased from 10 sets/exercise (week 1) to 32 sets/exercise (week 6). The 6-week RT program implemented was designed to involve higher RT volumes than ever investigated in this timeframe. Tests performed prior to training (PRE) and after weeks 3 (MID) and 6 (POST) included dual-energy x-ray absorptiometry (DXA), vastus lateralis (VL) and biceps brachii ultrasounds, and bioelectrical impedance spectroscopy (BIS). VL biopsies were also collected for immunohistochemical staining. Repeated-measures ANCOVAs were performed, although emphasis was also placed on effect size calculations. Results: The GWP group experienced the greatest PRE to POST reduction in DXA fat mass (FM) (-1.00 kg, d=- 0.24, p<0.05) and increase in DXA lean body mass (LBM) (+2.93 kg, d=0.33, p<0.05). DXA LBM increases (ΔLBM) occurred from PRE to MID (+1.34 kg, p<0.001) and MID to POST (+0.85 kg, p<0.001) across all groups. However, when adjusting ΔLBM for extracellular water changes, a significant increase occurred from PRE to MID (+1.18 kg, p<0.001), but not MID to POST (+0.25 kg; p=0.131). Conclusions: Larger effects on FM and LBM in GWP subjects indicates a need for longer-term investigations with greater sample sizes examining graded WP intakes and RT. Additionally, ECW-corrected LBM gains were largely dampened, but still positive, in resistance-trained subjects when RT exceeded ~20 sets/exercise/wk.