Serum concentration of cartilage oligomeric matrix protein (COMP) is sensitive to physiological cyclic loading in healthy adults

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. Blood samples (5 ml) were drawn from 10 physically active adults immediately before and after, and 0.5 h, 1.5 h, 3.5 h and 5.5 h 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 6 h 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 ( α = 0.05). 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 5.5 h 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). 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 5.5 h indicates a metabolic delay for COMP in the range of 5 h to 6 h.