How much does sleep matter for building muscle?

A lot. Adults need at least 7 hours a night, according to sleep medicine experts. In one study, a single night without sleep cut muscle protein building by 18 percent in young adults, and a review found several short nights in a row can lower strength on big lifts like squats and bench press. Regular, sufficient sleep supports your training.

What the research found

• Muscle building: in a 2021 study, one night of no sleep reduced muscle protein synthesis by 18 percent. It also raised cortisol and lowered testosterone the next morning.
• Strength: a 2018 review found a single night without sleep had little effect on strength. Several nights of short sleep in a row reduced force on multi-joint lifts like squats.
• How much: the American Academy of Sleep Medicine and the Sleep Research Society recommend at least 7 hours a night for adults.
• Hormones: the same 2021 study found cortisol rose by about a fifth after the sleepless night, a sign of a more catabolic state.

Better sleep, simply

• Keep the same bedtime and wake time, even on weekends.
• Keep your room dark, quiet and cool.
• Finish hard workouts and caffeine a few hours before bed if they keep you up.
• Put the phone away for the last half hour.

If you snore loudly, stop breathing at night, or feel very sleepy in the day despite enough time in bed, talk to a doctor. Those can be signs of a sleep disorder.