The influence of walking speed on the mechanoresponsiveness of biomarkers.

PURPOSE: The goal of this study was to examine short-term biomarker responses to walking at three different speeds in healthy individuals. MATERIALS AND METHODS: Healthy participants completed three study visits. At each visit, participants rested supine for 45 minutes, after which blood was collected. Next, participants completed a 30-minute treadmill walk, and another blood sample was collected. Finally, participants rested in a supine position for 45 minutes, after which a third blood sample was collected. At each visit, the treadmill speed was varied so that participants walked at a slow, moderate, or brisk speed. Serum biomarker levels were measured for cartilage oligomeric matrix protein (COMP), matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and lubricin (PRG4). RESULTS: Both COMP (p < 0.0001) and MMP-3 (p < 0.0005) showed significant increases in serum levels between pre- and post-activity measurements. The concentrations of both COMP (p < 0.0001) and MMP-3 (p = 0.04) decreased significantly from the post-activity to the recovery timepoint. Increasing walking speed elicited an increase in both serum COMP and MMP-3 concentrations (p < 0.05). On the other hand, we did not detect alterations in serum IL-6 or PRG4 concentrations due to walking or recovery. CONCLUSIONS: Given the relationship we found between biomarker levels and walking speed, COMP and MMP-3 may be biomarkers reflective of the cartilage response to mechanical loading. Furthermore, these data suggest that mechanical loading through exercise may be a means to detect aberrant mechanical response. Finally, these findings serve as important baseline data for future studies investigating biomarker levels in those at risk for OA.