Side-to-side differences in bone strength in master jumpers and sprinters

A. Ireland (1), M. Korhonen (2), A. Heinonen (2), H. Suominen (2), C. Baur (3), S. Stevens (1), H. Degens (1), J. Rittweger (1,4)

(1) Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, United Kingdom;
(2) Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland;
(3) Novotec Medical, Pforzheim, Germany;
(4) Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany

Abstract
Introduction: This study evaluated side-to-side difference in tibial bone structure, calf muscle cross-sectional area (CSA) and hopping force in master athletes as a result of training for sports with different magnitudes of inter-leg loading difference. Methods: Tibial bone parameters (at 4%, 14%, 38% and 66% tibial length proximal to distal end), muscle CSA (at 66% tibial length) and hopping forces of both legs of 51 master athletes (conditioned jumpers, conditioned triple jumpers, unconditioned jumpers, hurdlers and sprinters) were examined using pQCT. In epiphyseal 4% slice bone CSA (Ar.tot), total BMC (vBMC.tot), trabecular BMC (vBMC.tb) cortical BMC (vBMC.ct), and trabecular BMD (vBMD.tb) were measured. In diaphyseal slices, Ar.tot, vBMC.ct, cortical density (vBMD.ct), cross-sectional moment of inertia (CSMI) and calf muscle CSA (MuscA) were examined. Results: In conditioned jumpers, side-to-side differences in favour of take-off leg were found in 4% slice in vBMC.tb (+4.1%) (P<0.05). A side-to-side difference was found in 66% slice vBMC.ct and CSMI (both P<0.05), with conditioned jumper (+2.8% and 6.6%) and triple jumper (+2.7% and 7.2%) values higher than other groups. Conclusion: The results suggest that regular training in highimpact sports with uneven lower limb loading results in side-to-side differences in skeletal adaptation independent of age and gender, suggesting that high-impact exercise is effective in maintaining bone strength throughout human lifespan.

Keywords: Ageing, Exercise, Loading, pQCT