ORIGINAL ARTICLES  SPORTS INJURIES AND REHABILITATION 

The Journal of Sports Medicine and Physical Fitness 2014 October;54(5):651-7

Copyright © 2014 EDIZIONI MINERVA MEDICA

lingua: Inglese

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

Tsuchiya Y. ^{1, 2}, Sakuraba K. ^{1, 3}, Ochi E. ⁴ ✉

¹ Graduate School of Medicine, Juntendo University, Tokyo, Japan; ² Laboratory of Growth and Development, Nippon Sport Science University, Tokyo, Japan; ³ Laboratory of Sports Medicine, Juntendo University, Tokyo, Japan; ⁴ Laboratory of Health and Sports Sciences, Meiji Gakuin University, Yokohama, Japan

AIM: This study aimed to investigate the effects of eccentric contractions (ECs) of the biceps brachii muscle on bone metabolism markers.
METHODS: 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).
RESULTS: 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).
CONCLUSION: We conclude that a single bout of ECs of the biceps has a negative effect on bone metabolism in the acute phase.