Acute changes in knee cartilage transverse relaxation time after running and bicycling

PURPOSE: To compare the acute effect of running and bicycling of an equivalent cumulative load on knee cartilage composition and morphometry in healthy young men. A secondary analysis investigated the relationship between activity history and the change in cartilage composition after activity. METHODS: In fifteen men (25.8±4.2 years), the vertical ground reaction force was measured to determine the cumulative load exposure of a 15-min run. The vertical pedal reaction force was recorded during bicycling to define the bicycling duration of an equivalent cumulative load. On separate visits that were spaced on average 17 days apart, participants completed these running and bicycling bouts. Mean cartilage transverse relaxation times (T₂) were determined for cartilage on the tibia and weight-bearing femur before and after each exercise. T₂ was measured using a multi-echo spin-echo sequence and 3T MRI. Cartilage of the weight bearing femur and tibia was segmented using a highly-automated segmentation algorithm. Activity history was captured using the International Physical Activity Questionnaire. RESULTS: The response of T₂ to bicycling and running was different (p=0.019; mean T₂: pre-running=34.27ms, pre-bicycling=32.93ms, post-running=31.82ms, post-bicycling=32.36ms). While bicycling produced no change (-1.7%, p=0.300), running shortened T₂ (-7.1%, p<0.001). Greater activity history predicted smaller changes in tibial, but not femoral, T₂. CONCLUSIONS: Changes in knee cartilage vary based on activity type, independent of total load exposure, in healthy young men. Smaller changes in T₂ were observed after bicycling relative to running. Activity history was inversely related to tibial T₂, suggesting cartilage conditioning.