Effects of different modes of exercise on skeletal muscle mass and function and IGF-1 signaling during early aging in mice

Skeletal muscle mass and function tend to decline with increasing age. Insulin-like growth factor 1 (IGF-1) plays a key role in promoting skeletal muscle growth. Exercise improves skeletal muscle mass and function via the activation of IGF-1 signaling. The aim of this study was to investigate whether different types of exercise can promote muscle hypertrophy, exercise and metabolic capacities, and activate IGF-1 signaling during early aging in mice. We randomly assigned 12 month old male C57/BL6 mice into five groups: control, aerobic exercise, resistance exercise, whole-body vibration and electrical stimulation group. Gastrocnemius muscle mass, myofiber size, levels of IGF-1 signaling, oxidative stress, protein synthesis and degradation, and apoptosis were detected. C2C12 cells were used to explore the mechanism by which exercise exerts its effects. We confirmed that the four modes of exercise increased skeletal muscle mass, exercise capacity, indicators of metabolism and protein synthesis, and inhibited oxidative stress and apoptosis via activation of the IGF-1 pathway. The most effective intervention was resistance exercise. Whole-body vibration promoted muscle hypertrophy better than aerobic exercise. Furthermore, in the in vitro experiment, the importance of IGF-1/IGF-1R-PI3K/Akt signaling for maintaining skeletal muscle mass was confirmed. Aerobic exercise, resistance exercise, whole-body vibration and electrical stimulation increased skeletal muscle mass, exercise capacity, protein synthesis and metabolic enzyme activity, and inhibited protein degradation and apoptosis in mice undergoing early aging via activation of IGF-1 signaling. Of these, whole-body vibration has been shown to be significantly effective and is similar to conventional exercise in promoting muscle hypertrophy.