Strength Training Induced Expressiom Of Mechano-growth Factor In Human Skeletal Muscle

Abstract

0390 It has been recently demonstrated that a variant of the insulin-like growth factor named mechano-growth factor (MGF) is upregulated in human skeletal muscle in response to mechanical load. Previous studies have shown that MGF may be involved in the cellular procedure of muscle hypertrophy and muslce regeneration, and therefore may play an important role in the muscular adaptation to physical training. PURPOSE: To investigate the expression of MGF at mRNA level in human skeletal muscle in response to strength training with different strategies. METHODS: 24 male sports students (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 (different external force-speed and muscle-action requirements), 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. Muscls samples were attained from mfitriceps brachii before and at the end of the training using fine needle biopsy technique. Total RNA was extracted from the muscle samples and Oligo primed synthesis of cDNA was performed using MuLV reverse transcriptase. MGF mRNA level was determined using quantitative real-time PCR with relation to internal house-keeping gene (HPRT). RESULTS: Strength training produced a significant increase in 1RM in both groups (5.6 kg for MAX-group and 5.0 kg for COMBI-group, respectively), and the combined strength training led an additional improvement in maximum movement velocity (0.1 m/s, p < 0.05). In comparison with that before training (100%), MGF mRNA was significantly upregulated (565% for MAX-group and 171% for COMBI-group, respectively, p < 0.01). CONCLUSION: It can be demonstrated that MGF mRNA could be significantly upregulated in human skeletal muscle in response to the strength training, and MGF mRNA level can be affected by different training patterns. Because a transformation of myosin heavy chain isoforms has been observed in this study (JAP, 94:2282, 2003), MGF might be involved in this transformation and therefore play an important role in the muscle adaptation to strength training.