Sleep is the training variable you are not periodising

Athletes track load to the kilometre and to the kilogram, then treat sleep as whatever is left over after the day. The evidence says sleep is the largest recovery input you have, and the one most training plans never see.

The injury number

Milewski and colleagues followed 112 adolescent athletes for 21 months. Those sleeping under eight hours were 1.7 times more likely to be injured than those sleeping eight or more, and hours of sleep was one of the two best independent predictors of injury in the whole dataset, ahead of training volume. Adults are not adolescents, but the mechanism, slower reaction time and poorer motor control on short sleep, does not retire at twenty.

The performance number

The Stanford basketball study went the other way: instead of measuring the cost of short sleep, Cheri Mah asked eleven varsity players to sleep as much as they could for five to seven weeks. Free-throw accuracy rose 9%, three-point accuracy 9.5%, and sprint times fell about 5%. No change in training. Just more nights of the thing training is supposed to be converted by.

Five percent on a sprint is the difference between a block of speed work and none. It is a training effect, delivered by a pillow.

Why plans ignore it

Because plans are written in advance and sleep happens afterwards. A block that prescribes threshold on Tuesday cannot know that Monday night was five hours. The runner either does the session badly, or skips it and feels they failed the plan. Neither is what the plan intended.

The fix is a plan that reads last night before it commits to today. That means the coach needs the sleep data, needs a baseline for what your normal night is, and needs the authority to move the session.

How PeakU periodises it

PeakU pulls sleep duration and sleep score from whatever wrote them to Health Connect, scores them against your own baseline, and lets them move the day's call. Two short nights in a row pull quality work later in the week and swap in easy volume; a run of good nights lets the plan hold its ramp. The weekly review names sleep explicitly when it was the thing that slipped, because a plan that quietly absorbs your bad nights teaches you nothing.