The basic rest–activity cycle (BRAC) is a physiological arousal mechanism in humans proposed by Nathaniel Kleitman,[1] hypothesized to occur during both sleep and wakefulness.
When awake, brainwaves are faster during the first half of the cycle which corresponds to feeling alert and focused.
Kleitman hypothesized that the short-term 50 minute ultradian cycle of infants observed by researchers Denisova and Figurin ensured that a newborn infant would have frequent opportunities to respond to the stimulus of hunger pangs by waking up and crying, and would therefore get adequate nutrition.
[3] Kleitman concluded that BRAC tended to lengthen with age based on research published from Ohlmeyer and Brilmeyer.
[5] Despite research centering on the nocturnal evidence, the BRAC is often used as a time management and productivity tool.