High force eccentric exercise enhances serum tartrate-resistant acid phosphatase-5b and osteocalcin

We investigated the effects of eccentric contractions (ECs) on bone metabolism markers and the relationship between bone metabolism and skeletal muscle related protein. Seventeen young untrained men were divided into two groups and performed either 60 or 30 maximal ECs. We measured serum levels of osteocalcin (OC), bone alkaline phosphatase, cross-linked N-telopeptide of type I collagen (NTx), and tartrate-resistant acid phosphatase 5b (TRACP-5b), growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Blood samples were collected for up to five days after ECs. OC with 60 ECs were significantly higher than with 30 ECs (2 hours; p<0.05, day 1 and day 5; p<0.01). TRACP-5b with 60 ECs were significantly higher than with 30 ECs (day 3 and day 5; p<0.001). IGF-1 and OC were significantly positively correlated with 60 ECs (2 hours, day 1, and day 5; p<0.05). There were also significant positive correlations between IGF-1 and NTx with 60 ECs (2 hours, p<0.01; day 1, p<0.05). We found that one bout of severe ECs caused increases in OC and TRACP-5b, which promote increased bone metabolism. Our results suggest that contraction-induced IGF-1 may activate OC and NTx in acute response.