It is well know that heavy resistance training (RT) promote skeletal muscle hypertrophy (Andersen &Aagaard 2010). In particularly some studies have shown that this kind of training tends to decrease the expression of MHC IIx and MHC I and, at the same time, increase the expression of MHC IIa. But gender differences in such kind of changes are not known. The aim of this study was to analyse the differences in gender response after two months of RT. Furthermore, we wanted to compare the changes in latissimus dorsi muscle fibres characteristics with the mechanical measurement of fibres. Methods: Eighteen healthy volunteers participated in 8-week progressive resistance training for upper limbs muscles. One repetition maximal test was performed and mechanical and myosin characterization (Pietrangelo et al. 2009) of latissimus dorsi muscle fibres were analysed pre and post- training. We used a fine needle biopsy technique that allowed us to obtain about 4 mg of muscle sample (Paoli et al. 2010). Results: The increase in 1RM after 8-weeks of training was significantly greater in women (+24%) compared to men (+13%). The electrophoretic analysis of muscle fibers showed some changes in MHC expression. We observed an increased in MHC IIa (male +13% and female +33%) and a decrease in MHC IIx (male -8% and female -26%) while the MHC I expression in male tends to decrease (-5%) and in female tends to increase (+6%). Interestingly, the two-way ANOVA analysis (time x gender) showed a gender significant difference for female only in MHC IIa expression. The mechanical analysis of single fibres showed that training increased significantly the cross sectional area (CSA) and fibre strength in male and muscle fibre tension both in male and female. Discussion: The greater increase of 1RM performance with a substantial unchanged fibre CSA in female subjects could be explained by an improved motor units recruitment whilst males response to training seems oriented to hypertrophy. Moreover also myosin changes showed a gender related difference. Taken together our results suggest that resistance training effects on muscle are gender specific and more work is needed to explain this difference.
© Copyright 2012 17th Annual Congress of the European College of Sport Science (ECSS), Bruges, 4. -7. July 2012. Veröffentlicht von Vrije Universiteit Brussel. Alle Rechte vorbehalten.