Guest guest Posted November 20, 2008 Report Share Posted November 20, 2008 The main finding of the below study was that light load (LL) resistance training (15.5%RM) was sufficient to induce a small but significant muscle hypertrophy in healthy young men. However, LL resistance training was inferior to heavy load (70%1RM) training in evoking adaptive changes in muscle size and contractile strength and was insufficient to induce changes in MHC composition. Changes in muscle size and MHC composition in response to resistance exercise with heavy and light loading intensity J Appl Physiol 105: 1454-1461, 2008. First published September 11, 2008; L. Holm,1 S. Reitelseder,1 T. G. Pedersen,1 S. Doessing,1 S. G. sen,1 A. Flyvbjerg,2 J. L. Andersen,1 P. Aagaard,3 and M. Kjaer1 Muscle mass accretion is accomplished by heavy-load resistance training. The effect of light-load resistance exercise has been far more sparsely investigated with regard to potential effect on muscle size and contractile strength. We applied a resistance exercise protocol in which the same individual trained one leg at 70% of one-repetition maximum (1RM) (heavy load, HL) while training the other leg at 15.5% 1RM (light load, LL). Eleven sedentary men (age 25 ± 1 yr) trained for 12 wk at three times/week. Before and after the intervention muscle hypertrophy was determined by magnetic resonance imaging, muscle biopsies were obtained bilaterally from vastus lateralis for determination of myosin heavy chain (MHC) composition, and maximal muscle strength was assessed by 1RM testing and in an isokinetic dynamometer at 60°/s. Quadriceps muscle cross-sectional area increased (P < 0.05) 8 ± 1% and 3 ± 1% in HL and LL legs, respectively, with a greater gain in HL than LL (P < 0.05). Likewise, 1RM strength increased (P < 0.001) in both legs (HL: 36 ± 5%, LL: 19 ± 2%), albeit more so with HL (P < 0.01). Isokinetic 60°/s muscle strength improved by 13 ± 5% (P < 0.05) in HL but remained unchanged in LL (4 ± 5%, not significant). Finally, MHC IIX protein expression was decreased with HL but not LL, despite identical total workload in HL and LL. ===================== Carruthers Wakefield, UK Quote Link to comment Share on other sites More sharing options...
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