title: Serum concentration of cartilage oligomeric matrix protein (COMP) is sensitive to physiological cyclic loading in healthy adults.
abstract: OBJECTIVE
  To test the hypothesis that physiological cyclic loading during a 30-min walking exercise causes an increase in serum cartilage oligomeric matrix protein (COMP) concentration in a healthy population.
  
  
  METHODS
  Blood samples (5 ml) were drawn from 10 physically active adults immediately before and after, and 0.5h, 1.5h, 3.5h and 5.5h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. On a separate day, blood samples were drawn from the same 10 subjects during 6h while they were resting in a chair. Serum COMP concentrations were determined using a commercial enzyme-linked immunosorbent assay (COMP ELISA). An activity monitor was used to record basic time-distance measurements of gait. Serum COMP concentrations within the exercise protocol and within the resting protocol were compared using separate repeated measures analyses of variance (alpha=0.05).
  
  
  RESULTS
  In the exercise protocol, a first increase (9.7%; P=0.003) occurred immediately after the walking exercise. A second increase in serum COMP concentration (7.0%; P=0.024) occurred 5.5h after the walking exercise. In the resting protocol, the concentration at baseline was significantly higher than at all subsequent time points (8.2%; P<0.050). Serum COMP concentration decreased from the 3.5-h to the 5.5-h sample (-4.8%; P=0.012).
  
  
  CONCLUSIONS
  Even a moderate walking activity can significantly influence serum COMP concentration. The immediate response points to a diffusion time of COMP fragments from cartilage to the blood of 30 min or less. The response at 5.5h indicates a metabolic delay for COMP in the range of 5h to 6h.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, CA, USA. amuender@stanford.edu
authors.forename: Annegret
authors.initials: A
authors.lastname: Mündermann
authors.forename: Chris O
authors.initials: CO
authors.lastname: Dyrby
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Andriacchi
authors.forename: Karen B
authors.initials: KB
authors.lastname: King
mesh_terms: D000328:Adult; D064236:Cartilage Oligomeric Matrix Protein; D002358:Cartilage, Articular / Q000378:metabolism / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000097:blood*; D005260:Female; D005684:Gait / Q000502:physiology; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D008297:Male; D064235:Matrilin Proteins; D012016:Reference Values; D013997:Time Factors; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D064236:Cartilage Oligomeric Matrix Protein; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; C577553:TSP5 protein, human