Purpose: To investigate acute changes in biochemical markers of bone and cartilage turnover in response to moderate intensity exercise with and without joint impact in healthy human subjects.

Methods: A randomized, cross-over, exploratory, clinical study was conducted. Twenty healthy subjects with no history of joint trauma completed 30 min interventions of standardized moderate intensity cycling and running as well as a resting intervention 1 week apart. Blood samples were taken immediately before, four times after exercise and again the next day. Urine was sampled, before, after and the next day. On the day of rest, samples were taken at timepoints similar to the days of exercise. Markers of type I (CTX-I), II (C2M, CTX-II) and VI (C6M) collagen degradation, cartilage oligomeric matrix protein (COMP) and procollagen C-2 (PRO-C2) was measured.

Trial registration number: NCT04542655, 02 September 2020, retrospectively registered.

Results: CTX-I was different from cycling (4.2%, 95%CI: 0.4-8.0%, p = 0.03) and resting (6.8%, 95%CI: 2.9-10.7%, p = 0.001) after running and the mean change in COMP was different from cycling (10.3%, 95%CI: 1.1-19.5%, p = 0.03), but not from resting (8.6%, 95%CI: - 0.7-17.8%, p = 0.07) after running. Overall, changes in other biomarkers were not different between interventions.

Conclusion: In this exploratory study, running, but not cycling, at a moderate intensity and duration induced acute changes in biomarkers of bone and cartilage extra-cellular matrix turnover.