In for the long haul: the sleeping-competing connection

As a consequence of the Earth spinning on its axis and orbiting the sun, there are repeating fluctuations in light, warmth and seasons. Having evolved on this planet, it would therefore be amazing if these rhythms were not imprinted deeply into human physiology, and indeed they are. There are many biological rhythms that are integral to human physiology, but of these, the daily 24-hour night/day ‘circadian’ rhythm is the most powerful. The circadian rhythm affects hormone secretions, body temperature, mental alertness and physical performance capacity through the day. To understand just how important this rhythm is, see figure 1, which shows the typical daily variations of melatonin, secretion, core temperature, triacylglycerol, alertness and reaction time as a result of daily circadian fluctuations⁽¹⁾.

Figure 1: Typical circadian rhythm-induced fluctuations in the body