The Effect of Vigorous Running and Cycling on Novel Markers of Knee Joint Function

Abstract

To date, no study has been undertaken to compare the effects of running (weight-bearing) and cycling (non-weight bearing) exercise on biomarkers of knee joint loading. PURPOSE: To investigate knee articular cartilage deformation and changes in serum oligomteric matrix protein (COMP) and lubricin in response to vigorous recreational exercise. We tested the hypothesis that the mode of biomechanical loading of the knee joint (weight-bearing versus non-weight bearing) would influence the nature of the responses. METHODS: 11 male runners (age: 40±6 years; weight: 76±8 kg; VO2max: 4.3±0.3 L/min mean±SD) and 11 male cyclists (35±12 years; 75±5 kg; 4.4±0.6 L/min) were investigated. Venous blood samples and supra-patellar ultrasound imaging scans were obtained at baseline rest, immediately after, and 30 minutes after, vigorous exercise (time trial: either 10 km run or 25 km cycle). Knee cartilage thicknesses and serum COMP and lubricin (ELISA) were determined for each time point. Statistical analyses were performed using two-factor repeated measures (group x time) ANOVA. RESULTS: At baseline rest, there were no significant differences between groups for cartilage thicknesses measured at the intercondyle notch, medial condyle and lateral condyle. Vigorous exercise did not result in significant change in any of the cartilage thicknesses for either group. There were no significant differences between runners and cyclists for COMP (runners: 804.1±87.5 ng/ml; cyclists: 693.0±84.7 ng/ml) and lubricin (runners: 104.0±19.8 ng/ml; cyclists: 119.1±23.9 ng/ml) at baseline. For both groups, vigorous exercise was generally accompanied by an increase in both serum COMP (cyclists: 32.1%; p < 0.05; runners: 14.2%; p = 0.14) and lubricin (cyclists: 39.4%; p < 0.05; runners 56.9%; p < 0.05). Following 30 minutes of rest, serum COMP and lubricin decreased towards baseline values in both groups (p < 0.05). CONCLUSIONS: In the absence of ultrasonographic evidence of knee cartilage deformation, responses of lubricin following an acute bout of vigorous exercise is not influenced by the modality of knee joint loading, and may reflect a temporary increase in joint lubrication. However, changes in cartilage metabolism following exercise, as measured by serum COMP, may be dependent on the exercise modality.