The deleterious effects of bed rest on human skeletal muscle fibers are exacerbated by hypercortisolemia and ameliorated by dietary supplementation

Am J Physiol Cell Physiol. 2007 Jul;293(1):C313-20. doi: 10.1152/ajpcell.00573.2006. Epub 2007 Apr 4.


Prolonged inactivity associated with bed rest in a clinical setting or spaceflight is frequently associated with hypercortisolemia and inadequate caloric intake. Here, we determined the effect of 28 days of bed rest (BR); bed rest plus hypercortisolemia (BRHC); and bed rest plus essential amino acid (AA) and carbohydrate (CHO) supplement (BRAA) on the size and function of single slow- and fast-twitch muscle fibers. Supplementing meals, the BRAA group consumed 16.5 g essential amino acids and 30 g sucrose at 1100, 1600, and 2100 h, and the BRHC subjects received 5 daily doses of 10-15 mg of oral hydrocortisone sodium succinate throughout bed rest. Bed rest induced atrophy and loss of force (mN) and power (muN.FL.s(-1)) in single fibers was exacerbated by hypercortisolemia where soleus peak force declined by 23% in the type I fiber from a prevalue of 0.78 +/- 0.02 to 0.60 +/- 0.02 mN post bed rest (compared to a 7% decline with bed rest alone) and 27% in the type II fiber (1.10 +/- 0.08 vs. 0.81 +/- 0.05 mN). In the BRHC group, peak power dropped by 19, 15, and 11% in the soleus type I, and vastus lateralis (VL) type I and II fibers, respectively. The AA/CHO supplement protected against the bed rest-induced loss of peak force in the type I soleus and peak power in the VL type II fibers. These results provide evidence that an AA/CHO supplement might serve as a successful countermeasure to help preserve muscle function during periods of relative inactivity.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Amino Acids, Essential / administration & dosage*
  • Bed Rest / adverse effects*
  • Chronic Disease
  • Cushing Syndrome / chemically induced
  • Cushing Syndrome / complications*
  • Cushing Syndrome / pathology
  • Cushing Syndrome / physiopathology
  • Dietary Sucrose / administration & dosage*
  • Humans
  • Hydrocortisone / analogs & derivatives
  • Male
  • Muscle Contraction / drug effects
  • Muscle Fibers, Fast-Twitch / drug effects
  • Muscle Fibers, Fast-Twitch / pathology
  • Muscle Fibers, Slow-Twitch / drug effects
  • Muscle Fibers, Slow-Twitch / pathology
  • Muscle Strength / drug effects
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiopathology
  • Muscular Atrophy / etiology*
  • Muscular Atrophy / pathology
  • Muscular Atrophy / physiopathology
  • Muscular Atrophy / prevention & control*
  • Time Factors
  • Treatment Outcome


  • Amino Acids, Essential
  • Dietary Sucrose
  • hydrocortisone hemisuccinate
  • Hydrocortisone