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regulates · 5
Short sleep drags down reaction, attention and judgment first, so skilled actions in sport, which need focus and precision, suffer most. In a meta-analysis that pooled 69 studies, skilled actions got worse by 20.9% on average after short sleep while maximal strength fell by only 2.85%, and the authors put the difference down to the higher demands skill makes on the brain; after one night without sleep, reaction time was also 8% longer.
The talk test and perceived effort read how the body is responding right now, not a fixed pace or weight, so on short sleep they scale the intensity down on their own. In one experiment, 11 men ran for 30 minutes at their own pace after 30 hours awake; their perceived effort was about the same as after normal sleep, yet they covered less distance. If you can still talk in full sentences fairly comfortably, you are below the ventilatory threshold.
On short sleep, reaction and skill decline first, which makes mistakes in contact and complex movements more likely; that is the reason to drop contact, technical work and heavy sets close to failure first on a short-sleep day. In a retrospective study of 112 adolescent athletes, those who slept less than 8 hours a night on average were 1.7 times as likely to have had an injury; that is an observed association and cannot show that short sleep caused it.
In the months after birth when you get up at night to feed, sleep is broken into pieces, and exercise then helps more than the body alone. The American College of Obstetricians and Gynecologists writes that physical activity can be an important factor in preventing postpartum depression, and in a meta-analysis of 12 controlled trials, exercise during pregnancy and after birth lowered postpartum depressive symptoms, more so in mothers who already had them. Returning to training after birth follows the postnatal check and starts again from the lightest level.
←After birth and breastfeeding
In the first months after birth, total sleep each night averages about 7.2 hours, which sounds like plenty, but it is interrupted again and again: the hard part is broken sleep, not short sleep. These months are not the time to force hard training; short, easy activity that you can stop at any moment fits best, and a low mood that has not passed after two weeks may be postnatal depression and calls for a doctor.
contrast · 3
Daytime sleepiness can come from sleeping too little, or from an airway that keeps collapsing during sleep and chops it into pieces, and the two are often taken for the same thing. Sleep that is long enough yet never refreshing, or loud snoring with daytime sleepiness so strong that you fall asleep whenever you sit down, is not something scaling down your training will fix; if you nod off while driving, stop driving and get a sleep study soon.
A walk outside in the daytime is often treated as advice that suits everyone: light travels through the retina to the brain's master clock in the hypothalamus and aligns it with the day. For someone coming off a night shift, though, morning light on the way home pushes the clock the wrong way, so the rule is the opposite. Staying up after a night shift to train is also when you have been awake longest and perform worst: after short sleep, each extra hour awake before exercise lowered performance by about another 0.4% on average.
A strength plateau is often blamed on the training plan, but the cause may be sleep: a systematic review found that one night without sleep had little effect on maximal strength, and only after several nights of short sleep did strength in multi-joint lifts such as the squat fall, while single-joint movements did not.