What happens to your bones when you lie in bed for a long time?
Prolonged bed rest demonstrably leads to substantial bone loss, particularly in the hip, spine and heel bone. Recovery takes much longer than the period of bed rest itself, so resuming movement as soon as possible is the best thing you can do.
Bones are not static tissue. They are constantly being built up and broken down, and that balance depends heavily on movement and load. During prolonged bed rest, that mechanical stimulus disappears. Bone-forming cells become less active, while bone-breaking cells become more active. The result is measurable bone loss, and it happens faster than most people expect.
After 17 weeks of bed rest, healthy men lost an average of 3.9% of bone mass in the lumbar vertebrae and 4.6% in the hip. The heel bone, which normally absorbs a great deal of load, lost as much as 10.4%. Blood markers for bone breakdown rose clearly during bed rest. Researchers observed the same pattern in pregnant women prescribed bed rest: they lost an average of 4.6% of bone mineral in 20 weeks, compared with 1.5% in women who continued to move normally. The chance of losing more than 5% of bone mass was six times as high.
Recovery after bed rest is slow and far from always complete. After 17 weeks of bed rest and six months of being active again, only the heel bone had largely recovered. The spine and hip showed a positive trend but did not return to their previous level. Prevention is therefore far more effective than trying to recover after the fact.
In the long term, this bone loss increases the risk of fractures, particularly in the vertebrae and hip. Vertebral fractures are the most common complication of osteoporosis and can lead to chronic pain and loss of independence. Diet also plays a role: a diet high in animal protein and low in vegetables or fruit was associated with additional bone loss in the lumbar vertebrae during bed rest. Adequate calcium appears to be protective against this.
Based on multiple human studies, including a controlled 17-week bed-rest study in healthy men, a study in pregnant women, and research into bone markers during bed rest and spaceflight. No large randomised studies on recovery. The strength of evidence is strong for bone loss itself, moderate for recovery and fracture risk.