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Letters
April 25, 2007

Effect of 10 Days of Bed Rest on Skeletal Muscle in Healthy Older Adults

Author Affiliations
 

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2007;297(16):1769-1774. doi:10.1001/jama.297.16.1772-b

To the Editor: Older adults are more likely to be hospitalized and are at risk for functional decline during hospitalization. Bed rest may contribute to this functional compromise. We examined the effect of 10 days of bed rest in healthy older men and women on skeletal muscle protein synthesis, nitrogen balance, lean tissue mass, and lower extremity strength.

Methods

Twelve healthy older adults who were moderately active (mean [SD] age, 67 [5] years; 50% women) were recruited from advertisements and compensated for their participation. They remained in bed continuously for 10 days, except for toileting, and they consumed a eucaloric diet providing the recommended dietary allowance for protein (0.8 g/kg of protein per day). Measurements before and after bed rest included the fractional muscle protein synthesis rate over 24 hours, lean body mass by dual-energy x-ray absorptiometry (DEXA, Hologic Inc, Waltham, Mass), and unilateral knee extension strength (Cybex Strength Systems, Ronkonkoma, NY). Urinary nitrogen balance was determined before and during the bed rest period. Prophylactic measures were performed to prevent deep vein thrombosis, and ultrasound examination results were negative for all participants at the conclusion of the bed rest. One participant was excluded from all analyses due to insufficient protein intake; an additional participant was excluded from the DEXA analysis because a DEXA scan was not administered before bed rest, and another participant's fractional synthesis rate measurement was excluded because of a technical error.

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