Since the discovery of clock gene in mammals, the physiological role of the internal clock, which produces a rhythm of approximately 24 h per day, has been revealed, and it has become clear that a regular life rhythm is important for maintaining good health. Skeletal muscle function is no exception, and has been reported to be regulated by the internal clock. In the skeletal muscle, more than 2300 genes exhibit circadian rhythms and are involved in a wide range of functions, including myogenesis, transcription, and metabolism. In this chapter, we discuss the effects of exercise on the regulation of the skeletal muscle internal clock and its potential timing effects, starting from the regulation of skeletal muscle function by the internal clock.