"Tim Ferriss discusses how there needs to be more of a reason than tissue regeneration for sleep. According to Sapolsky (2004), many scientists and doctors believe we need sleep so the brain can replenish its energy supplies. The brain weighs only about three percent of our total body weight, yet it consumes 25 percent of the total body energy expenditure! Deep wave sleep is when energy restoration occurs (stages three and four REM)."
"It’s very important that you don’t watch television or do things right before bed that stimulate the sympathetic nervous system (SNS). Once in a while, you might stay up for a late game, but you will have no shot at entering deep wave sleep while the SNS is cranking. I always have my athletes stretch, meditate, go for a light walk, or listen to some soothing music before bed. These types of activities help to activate the parasympathetic nervous system (PNS). In order for recovery to take place, you must be in PNS dominant mode."
"If you or your athletes are depriving themselves of sleep, a decrease in stress hormones doesn’t occur. Instead, they increase. To make matters worse, a lack of sleep will cause both growth hormones and sex hormones to decrease."
"As sleep is divided into stages, the roles of sleep likely depend upon the stage in question. Non-rapid eye movement (NREM) sleep appears to play a role in the restoration of the nervous system and energy conservation. Rapid eye movement (REM) sleep seems to be important in local brain regeneration and modulating emotions. REM sleep appears to prepare animals for waking behavior; animals awakened from NREM sleep demonstrate impaired sensorimotor function in comparison to those awakened from REM sleep (Horner et al. 1997)."
"Early work suggested that sleep deprivation could impact variables associated with body composition. One to two nights of complete sleep deprivation was associated with elevated 24-hour urinary nitrogen excretion (Scrimshaw et al. 1966), which might be expected to impair lean body mass accrual. Sleep deprivation also appears to elicit changes in appetite-related hormones that could influence food intake and body composition."
"Four days of sleep extension to ten hours per night reduced daytime sleepiness (Carskadon and Dement 1982), which might be expected to hinder performance. Kamdar and colleagues (2004) also found this as well as faster reaction times and improved moods after sleep extension."
"Sleep deprivation has been shown to impair the immune and endocrine systems (Reilly and Edwards 2007), which are crucial to recovery from exercise. Acute sleep deprivation has been shown to lower testosterone and aggression in men (Cote et al. 2012), which could reduce motivation in training and blunt adaptations due to the stimulatory effect of testosterone on muscle protein synthesis. Disrupted sleep has been associated with reductions in resting heart rate and core temperature (Vaara et al. 2009), aerobic capacity, and aerobic enzyme activity (Vondra et al. 2001)."
"The National Sleep Foundation provides the following generic recommendations:
•Ages 1–3 years old, 12–14 hours per night
•Ages 3–5 years old, 11–13 hours per night
•Ages 5–10 years old, 10–11 hours per night
•Ages 10-19 years old, 8.5–9.25 hours of sleep per night
•Adults, 7–9 hours of sleep per night"
Also look up Chad Aichs. He has written a lot on sleep and lifting.
Perhaps the second article closes the best, "Sleep is something that we should all strive to improve if we value our health and performance."