Bone Resorption Is Induced on the Second Day of Bed Rest: Results of a Controlled Crossover Trial

J Appl Physiol (1985). 2003 Sep;95(3):977-82. doi: 10.1152/japplphysiol.00264.2003.


The aim of the study was to analyze the kinetics of short-term changes in bone turnover. We studied in a randomized crossover design the effects of 6 days of bed rest on eight healthy male subjects (mean body wt: 70.1 +/- 5.7 kg; mean age: 25.5 +/- 2.9 yr). The metabolic ward period was divided into three parts: 4 ambulatory days, 6 days of either bed rest or non-bed rest periods, and 1 recovery day. The diet was identical in both bed rest and non-bed rest phases. Continuous urine collection started on the first day in the metabolic ward to analyze excretion of bone resorption markers, namely C-telopeptide (CTX) and N-telopeptide (NTX), creatinine, urea, and 3-methylhistidine. On the second ambulatory day and on the fifth day of bed rest or during the non-bed rest phase, blood was drawn to analyze bone formation markers and amino acid concentrations. Urinary calcium excretion was increased as early as the first day of bed rest (P < 0.01). CTX and NTX excretion stayed unchanged during the first 24 h of bed rest compared with the non-bed rest period. However, already on the second day, both resorption markers had increased significantly. NTX excretion increased by 28.7 +/- 14.0% (P < 0.01), whereas CTX excretion rose by 17.8 +/- 8.3% (P < 0.001). Creatinine, urea, and 3-methylhistidine excretion did not change. We conclude that 24 h of bed rest are sufficient to induce a significant rise in osteoclast activity in healthy subjects.

Publication types

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

MeSH terms

  • Adult
  • Amino Acids, Essential / metabolism
  • Bed Rest / adverse effects*
  • Biomarkers
  • Body Weight / physiology
  • Bone Resorption / pathology*
  • Calcium / urine
  • Collagen / urine
  • Collagen Type I
  • Creatinine / urine
  • Cross-Over Studies
  • Diet
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Kinetics
  • Male
  • Methylhistidines / urine
  • Muscle, Skeletal / anatomy & histology
  • Muscle, Skeletal / physiology
  • Osteogenesis / physiology
  • Peptides / urine
  • Time Factors
  • Urea / urine
  • Urodynamics / physiology


  • Amino Acids, Essential
  • Biomarkers
  • Collagen Type I
  • Methylhistidines
  • Peptides
  • collagen type I trimeric cross-linked peptide
  • Urea
  • Collagen
  • Creatinine
  • 3-methylhistidine
  • Calcium