Activation Of Satellite Cells In Human Skeletal Muscle In Response To Strength Training

Abstract

The activation of satellite cells (SC) in the skeletal muscle may be attributed to muscle growth, hypertrophy and regeneration, and thus may have an important role in muscular adaptation to exercise. Our previous studies show that strength training led to a transformation of myosin heavy chain isoforms along with an upregulation of muscle growth factors. PURPOSE To investigate the activation of SC in human skeletal muscle in response to strength training with different strategies. METHODS 24 male volunteers (mean, age: 25 y; height: 183 cm; body mass: 81 kg) were divided into two groups with regard to the different trainings (6 weeks, 3d/w), in MAX-group (traditional strength training with maximum loads): 5 series, 3 reps (3 RM load); in COMBI-group: 1st day: 5 series, 3 reps; 2nd day: 3 series, 10 ballistic concentric-only throw movement (30%); 3rd day: 3 series, 7 reps, stretch-shorten-typed push-ups. Muscle samples were attained from m. triceps brachii before and at the end of the training using fine needle biopsy technique. The expression of the myogenic factors, MyoD and myogenin, were taken as the markers of activation of SC, and their mRNA levels were essesssed through reverse transcriptional PCR using quantitative real-time PCR technique. RESULTS Strength training resulted in a significant increase in 1RM in both groups, and the combined strength training led an additional improvement in maximum movement velocity. In comparison with that before training (100%), Myo D mRNA increased by 107% in MAX-group, but decreased slightly by 18% in the COMBI-group (NS). The expression level of myogenin mRNA was significantly increased by 90% in MAX-group, but did not change in COMBI-group (by −8%, NS). CONCLUSION A strength training with maximum contractions caused a significant activation of the satellite cells in human skeletal muscle, while strength training with combination strategy did not. The different effects on SC activation may be attributed to the fact that in MAX-group the upregulation of the growth factors (IGF-1 and MGF) war higher than that in COMBI-group. Since an upregulation of growth factors and a transformation of myosin heavy chain isoforms have been previously observed, the activation of SC in response to strength training suggests that the SC activation may have an important role in the muscular adaptation to exercise training.