During complete bed rest, what is the approximate weekly loss of bone mass?

During complete bed rest, what is the approximate weekly loss of bone mass?

• A. 0.1% per week
• B. 5% per week
• C. 1% per week
• D. 10% per week

Answer: (C)

Loss of bone mass during complete bed rest occurs because removing weight-bearing mechanical load shifts the balance of remodeling toward resorption. Mechanical strain normally signals osteoblasts to form bone and helps limit osteoclast activity; when loading is eliminated, osteocytes sense the lack of strain and trigger more resorption with less formation, leading to disuse osteoporosis. The typical rate of loss is about 1% of bone mass per week, a rough average that can vary with age, nutrition, hormones, and baseline bone health. The smaller figure (0.1% per week) underestimates the effect, while much larger rates (5% or 10% per week) would imply far more rapid deterioration than is usually seen with standard immobilization.

Loss of bone mass during complete bed rest occurs because removing weight-bearing mechanical load shifts the balance of remodeling toward resorption. Mechanical strain normally signals osteoblasts to form bone and helps limit osteoclast activity; when loading is eliminated, osteocytes sense the lack of strain and trigger more resorption with less formation, leading to disuse osteoporosis. The typical rate of loss is about 1% of bone mass per week, a rough average that can vary with age, nutrition, hormones, and baseline bone health. The smaller figure (0.1% per week) underestimates the effect, while much larger rates (5% or 10% per week) would imply far more rapid deterioration than is usually seen with standard immobilization.