PHYS-34 · Principle
Will more sleep help my legs? How much do I need?
Lost sleep lowers next-day performance, most clearly after a sleepless night or an early wake-up. Need is individual, with no fixed target for all; many athletes sleep under 7 h.
How the body works, agreed across the reviews below; a study entry shows what one experiment measured.
Practical Application
Will more sleep help my legs? How much do I need? Lost sleep lowers next-day performance, most clearly after a sleepless night or an early wake-up. Need is individual, with no fixed target for all; many athletes sleep under 7 h.
What it means for training: protect the sleep opportunity before any recovery tool; after one short night move the key session or lower its targets (SYNTH-07).
What it does not mean: that effort will feel harder after a short night (judge by output), that a tracker's sleep stages are accurate (PHYS-46), or that weeks of extra sleep are proven to add speed.
Mechanism
Across 69 studies, 6 h or less of sleep lowered performance by a mean 7.6% in every exercise category; total deprivation and waking early harmed consistently, going to bed later not consistently, and each extra hour awake cost about 0.4% (REF-204, 89% men, heterogeneity 98%).
Proposed routes include an autonomic imbalance resembling overtraining and a rise in pro-inflammatory cytokines (Fullagar 2015); sleep problems may raise injury risk and slow recovery from injury (REF-205, narrative); habitual sleep under 7 h raised respiratory-infection risk in the wider population (REF-972).
Common misreading
"Everyone needs 8 hours"; "I feel fine, so the short night cost nothing"; "more deep-sleep minutes on my ring means better recovery".
Backs
SYNTH-07 "Not from a study in this base; the base's own practice: a regular sleep opportunity of 7-9 h a night" (the direction; the hours stay practice) · SYNTH-70 "Lost sleep lowers next-day performance" (the loss; extension stays contested) · SYNTH-07 "one night of ≤6 h costs performance the same day"