Effect of eccentric contractions of elbow flexor on bone formation and resorption markers

This study aimed to investigate the effects of eccentric contractions (ECs) of the biceps brachii muscle on bone metabolism markers.

Eight untrained subjects (20.0±0.5 years) performed 5 sets of 6 maximal ECs of the elbow flexors with a 2-min rest interval between each set. Blood samples were collected at 6 time points: before (Pre) ECs, immediately after (Post) ECs, and two hours (2 hours), 1 (day 1), 3 (days 3), and 5 days (days 5) after ECs. We measured the levels of the bone formation marker osteocalcin (OC) and the resorption marker tartrate-resistant acid phosphatase 5b (TRACP-5b). In addition, we measured the isometric tetanic torque and the levels of myoglobin (Mb), creatine kinase (CK), blood lactate, and insulin-like growth factor-1 (IGF-1).

The results showed 1) CK and Mb levels increased significantly by days 3 and 5 (P<0.05); 2) OC levels significantly decreased in Post and 2 hours (P<0.01) and TRACP-5b levels significantly increased in Post (P<0.01); 3) OC positively correlated with the total work output in Post, 2 hours, and days 5 (Post: r=0.79, P<0.05; 2 hours: r=0.82, P<0.01; days 5: r=0.79, P<0.05); and 4) TRACP-5b levels positively correlated with IGF-1 levels (r=0.69, P<0.01).

We conclude that a single bout of ECs of the biceps has a negative effect on bone metabolism in the acute phase.