Effects of Sleep Deprivation on Acute Skeletal Muscle Recovery after Exercise.

Plain-language summary

This study looked at how going without sleep affects muscle recovery after hard exercise. Ten men did 240 hard lengthening contractions of the thigh muscles, then either stayed awake for 48 hours or slept normally for three nights, in both orders. The researchers tracked muscle strength, creatine kinase (an enzyme that leaks out of damaged muscle, so a higher level means more damage), and a panel of hormones and inflammatory signals. Strength came back at the same rate either way, and so did the muscle damage marker. What changed was the hormonal picture: cortisol rose, the ratio of cortisol to testosterone rose with it, IGF-1 rose, and one inflammatory signal, IL-6, went up. Testosterone itself did not move.

Key findings

• Muscle strength recovered at the same rate with or without sleep.
• Creatine kinase, the marker of muscle damage, rose the same amount either way.
• No difference in testosterone was detected between the two conditions.
• Cortisol, the main stress hormone, rose without sleep, and so did the ratio of cortisol to testosterone.
• IGF-1, the body's main anabolic growth signal, also rose without sleep, which cuts against reading the hormone picture as simply catabolic.
• Of every inflammatory signal measured, only IL-6 rose.