Exercise Intensity and Rest Intervals Effects on Intracellular Signals and Anabolic Response of Skeletal Muscle to Resistance Training

Abstract

Moro, T, Monaco, L, Naro, F, Reggiani, C, and Paoli, A. Exercise intensity and rest intervals effects on intracellular signals and anabolic response of skeletal muscle to resistance training. J Strength Cond Res XX(X): 000–000, 2021—Resistance training (RT) is one of the most important stimuli for muscle hypertrophy, and it may play also an important role on weight loss and fatty acids oxidation. Clearly, RT affects anabolic pathways, but the differences among various training techniques has been poorly investigated. We sought to compare the effect of 2 different intensities of training: high-intensity interval resistance training (HIIRT) and traditional resistance training (TRT), on muscle signaling pathway. Nine young healthy subjects performed HIIRT and TRT protocol on 2 different occasions and with different legs on leg extension. High-intensity interval resistance training technique consisted of 3 sets of 6 repetitions (reps) at 6 repetition maximum and then 20 seconds of rest and 2 or 3 repetitions (until exhaustion) repeated for 3 times with 2′30″ rest between sets, whereas TRT consisted of 3 sets of 15 reps with 75 seconds of rest between sets. Biopsies from the vastus lateralis were taken at baseline (pre), immediately (0 hours) at the end of training, and 6 hours (6 h) and 24 hours (24 h) after training. Western blot and real-time polymerase chain reaction messenger RNA (mRNA) analysis were performed to assess muscle signaling pathway activation. In both protocols, rpS6 phosphorylation significantly increased at 6 hours (p < 0.05). Traditional resistance training showed a significant increase at 24 hours of AMPK phosphorylation compared with HIIRT (p < 0.05), whereas no significant differences between groups were found for other proteins. mRNA analysis showed no differences between protocols except for striated muscle activator of Rho signaling. The manipulation of resistance training intensity through incomplete/short recovery does not induce different molecular anabolic and metabolic responses compared with a TRT method. Trial Registration number: NCT04163120 retrospectively registered.