Sleep deprivation cuts strength, boosts fat use during exercise

A recent study involving trained young adults found that sleeping only four hours—or none at all—significantly impairs muscle performance. In men, execution speed in bench press and squat fell by 10‑15 %, while women saw a 7‑12 % drop in muscular endurance. The research links these declines to reduced neural coordination rather than muscle loss alone.

The same participants showed a paradoxical shift in fuel utilization during a cycling endurance test: after a night of no sleep, fat oxidation increased by about 15 % and carbohydrate use fell by 14 %. This change is driven by stress responses such as heightened cortisol, lowered insulin sensitivity, and increased sympathetic activity, rather than an improvement in metabolic efficiency. Overall, short‑term sleep loss hampers both strength and cognitive performance, and while the body burns more fat under stress, it does not translate into better athletic output.