Research brief · 2026-09-09
What Happens to Muscle During Bed Rest or Immobilisation?
Muscle does not wait weeks to notice it is not being used. A trial designed to measure how fast disuse atrophy begins, by Wall and colleagues in Acta Physiologica in 2013, put twenty-four healthy young men in a full leg cast for either five or fourteen days. After five days, quadriceps cross-sectional area had already fallen 3.5 percent and knee-extensor strength 9 percent. By fourteen days those losses had roughly doubled, to 8.4 percent of muscle area and 22.9 percent of strength.
The exact numbers vary a lot between studies, which is itself a finding. Thom and colleagues in Acta Physiologica Scandinavica in 2001 cast eight young women for ten days and measured an 11.8 percent drop in quadriceps size and a 41.6 percent drop in leg-extension strength, far steeper than the fourteen-day figures above. Differences in sex, sample size and the strength test used are the likely explanations; no study tested them head-to-head.
Countermeasures help, with limits. Oates and colleagues in Muscle and Nerve in 2010 had people wear a non-weight-bearing knee brace for two weeks; those doing a small volume of resistance exercise avoided the significant declines in fibre size and strength seen in the control group. At longer durations protection gets harder. The 2026 BRACE study in The Journal of Physiology tested sixty days of bed rest with cycling, with or without artificial gravity. The artificial-gravity group preserved fat-free mass and resting metabolic rate, but neuromuscular function deteriorated similarly across all groups.
The gaps are important. Nearly every trial enrolled healthy young adults, so the rates may not apply to older people or those recovering from illness. And none followed participants afterwards to see how long recovery takes. Anyone facing a period of immobility should talk with a physician or physiotherapist about what is appropriate for them.
Sources
- Wall BT, Dirks ML, Snijders T, et al. Substantial skeletal muscle loss occurs during only 5 days of disuse
- Acta Physiologica 2013
- Thom JM, Thompson MW, Ruell PA, et al. Effect of 10-day cast immobilization on sarcoplasmic reticulum calcium regulation in humans
- Acta Physiologica Scandinavica 2001
- Oates BR, Glover EI, West DW, et al. Low-volume resistance exercise attenuates the decline in strength and muscle mass associated with immobilization
- Muscle & Nerve 2010
- Martin-Rodriguez S, Mandic M, Laurens C, et al. Artificial gravity during prolonged bed rest preserves resting metabolic rate but not muscle function: Evidence from the BRACE study
- The Journal of Physiology 2026
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