FIGURE 2.

The entrainment of circadian rhythms by light and exercise. The central clock oscillator, which regulates rhythms of melatonin and body temperature, is located within the suprachiasmatic nucleus (SCN), while oscillators governing the sleep-wake cycle may exist in brain regions beyond the SCN (Yamanaka and Waterhouse, 2016; Yamanaka, 2020). Two potential pathways for entraining the central circadian rhythm through exercise are depicted: 1, exercise entrains the central clock directly; 2, exercise entrains oscillators in extra-SCN brain regions, which then transmit signals to the SCN. It is important to note that light serves as the most significant zeitgeber. The regulation of circadian rhythms by exercise can be influenced by the intensity of light, as exercise can impact the function of light perception or the entrainment process related to light.