Pareja-Blanco, F. , Rodriguez-Rosell, D. , Sanchez-Medina, L. , Sanchis-Moysi, J. , Dorado, C. , Mora-Custodio, R. , YAÑEZ GARCÍA, JUAN MANUEL, Morales-Alamo, D. , Perez-Suarez, I. , Calbet, J. A. L. , Gonzalez-Badillo, J. J.
No
Scand. J. Med. Sci. Sports
Article
Científica
3.623
1.541
01/07/2017
000402631100006
We compared the effects of two resistance training (RT) programs only differing in the repetition velocity loss allowed in each set: 20% (VL20) vs 40% (VL40) on muscle structural and functional adaptations. Twenty-two young males were randomly assigned to a VL20 (n=12) or VL40 (n=10) group. Subjects followed an 8-week velocity-based RT program using the squat exercise while monitoring repetition velocity. Pre- and post-training assessments included: magnetic resonance imaging, vastus lateralis biopsies for muscle cross-sectional area (CSA) and fiber type analyses, one-repetition maximum strength and full load-velocity squat profile, countermovement jump (CMJ), and 20-m sprint running. VL20 resulted in similar squat strength gains than VL40 and greater improvements in CMJ (9.5% vs 3.5%, P<0.05), despite VL20 performing 40% fewer repetitions. Although both groups increased mean fiber CSA and whole quadriceps muscle volume, VL40 training elicited a greater hypertrophy of vastus lateralis and intermedius than VL20. Training resulted in a reduction of myosin heavy chain IIX percentage in VL40, whereas it was preserved in VL20. In conclusion, the progressive accumulation of muscle fatigue as indicated by a more pronounced repetition velocity loss appears as an important variable in the configuration of the resistance exercise stimulus as it influences functional and structural neuromuscular adaptations.
Muscle strength; training to failure; muscle hypertrophy; fiber type; magnetic resonance imaging