MOLECULAR SIGNALLING RESPONSE TO SHORT DURATION HIGH INTENSITY/LOW VOLUME RESISTANCE TRAINING IN HUMAN SKELETAL MUSCLE.

Introduction Resistance training (RT) is one of the most important stimuli for muscle hypertrophy, but it may play also an important role on weight loss and fat acid (FA) oxidation increase. It has been largely demonstrated that RT affects anabolic signalling molecule phosphorylation but, considering the numerous variables of RT, the differences between training modalities has been till now poorly investigated. The aim of this study was to assess Akt, 4EBP1, S6 and AMPK, ACC signalling after a single bout of high-intensity resistance training (HIRT) and of traditional resistance training (TRT). Methods 12 healthy subjects performed in two different moments and with different legs HIRT and TRT protocol. HIRT consisted in 2 sets of 6/2/2 reps with incomplete rest between (20”) sets while TRT consisted of 4 sets x15 reps with 1’15” of rest between sets. Biopsies from the vastus lateralis were taken one week before training sessions (pre), immediately after (T0), 6 hours after (T6) and 24 hours after (T24) training. Results No significant differences were found at any of time points after exercise in AKT and 4EBP1 phosphorylation. There was a significant increase in S6 phosphorylation at T6 both in HIRT and TRT. S6-P remained at higher level even at T24. Exercise intensity does not seem to influence the response of AMPK: AMPK-P decreased after both kind of RT, with a greater decrease at T6 during TRT. On the other hand, pACC activity increased immediately after HIRT and decrease after TRT, no significant differences were measured at T6 and T24. mRNA analysis showed that HIRT seems to be more related to mechanical deformation (MGF), while the TRT seems to act on IGF-1 pathway. Discussion Our findings suggest that a less time commitment resistance training technique is, at least, equally effective to induce an increase of S6-P. The increase of the S6-P without a concomitant increase of AKT-P could be explained by an AKT-independent S6 phosphorylation. The increase of the phosphorylated form of ACC in HIRT, but not in TRT, may suggests a greater FA oxidation with high intensity/low volume resistance training compared to traditional technique. This data seems confirm that the manipulation of different variables of RT induces different molecular and metabolic responses related to the activation of specific muscle signaling pathways. References Andersen JL, Aagaard P. (2010). Scand J Med Sci Sports, 20(2), 32-8. Paoli A. AM J Physiol Endocrinol Metab. 2012 302: E387-E387. Paoli A et al. J Transl Med. 2012 Nov 24(10):237. Verdijk LB et al. Am J Clin Nutr. 2009 Feb 89(2):608-16. Paoli A et al. Clin Physiol Funct Imag (in press)