Big vs powerful : molecular signalling responses to hypertrophic and power resistance exercise modalities

Abstract

Introduction: The effects of resistance exercise (RE) loading on molecular signalling proteins, including those involved in protein translation and thus skeletal muscle hypertrophy have been extensively studied. However, there is little research on high power RE loading and molecular signalling proteins, and also on possible relationships between signalling proteins and recovery from RE loading. Methods: 7 young men (31±6 years, 178.9±4cms, 84.6±5 kgs) performed 1 hypertrophy loading session (HYP) (5x10 80% 1RM leg presses (LP)) and 1 power loading session (POW) (10x5 70% 1RM LP), with each session separated by 7 days, in a crossover design, prior and subsequent to 12 weeks of resistance training. Phosphorylated p70S6K1 at Thr389, p70S6K1 at Ser424, p38, ERK, rpS6, 4EBP1 assessed with western blotting of vastus lateralis (VL) tissue microbiopsied immediately post-exercise, but only for the post-training acute loading sessions. Mechanical work performed calculated using video recordings, and the relationship between mechanical work, kinetic energy and potential energy. Recovery from HYP was assessed everyday after exercise for 4 days, and from POW, for 2 days, via maximal isometric leg press force, static jump height, VL muscle thickness. Results: No significant differences in protein signalling within or between HYP and POW conditions. No correlations between mechanical work performed and changes in signalling proteins. Recovery from HYP: changes in static jumps immediately post-exercise correlated with changes in p-p70S6K1 at Ser424 (r=0.793, p= 0.033), p-rpS6 (r=0.821, p=0.023) and p-ERK (r=0.821, p=0.023), changes in muscle thickness inversely correlated with changes in p-p38 (r=-0.786, p=0.036)) and p-ERK (r=-0.786, p=0.023) at 72h. Recovery from POW: changes in isometric LP immediately post-exercise correlated with changes in p-rpS6 (r=0.786, p=0.014), but changes in p-p70S6K at Thr389 (r=-0.929, p=0.003) inversely correlated with static jump height at 48h. Discussion: Lack of any significant differences within and between HYP and POW conditions for phosphorylated proteins might be because of the biopsy time-point, small sample size, or participants’ trained status. Correlations between some phosphorylated proteins and early recovery suggests that quicker recovery from resistance loading is associated with increased phosphorylation of signalling proteins after hypertrophy type loading. Conclusion: No differences in molecular signalling proteins involved in protein translation as a result of HYP versus POW. There were divergent intra and inter-individual signalling responses to HYP versus POW. No relationships between mechanical work performed and changes in signalling proteins. In conclusion, in trained young men, leg pressing 5x10 at 80% of 1RM results in similar acute molecular signalling changes as 10x5at 70% of 1RM.