Bone mineral density in flatwater sprint kayakers

To elucidate the possible skeletal benefits of the muscular contractions an d the nonweight-bearing loading pattern associated with kayaking, we invest igated the bone mineral density (BMD, g/cm(2)) of 10 elite kayakers, six ma les and four females, with a median age of 19 years. Each subject was compa red with the mean value of two matched controls. BMD of the total body, hea d, ribs, humerus, legs, proximal femur (neck, wards, trochanter), spine, lu mbar spine, and bone mineral content (BMC, g), of the arms was obtained usi ng a dual energy X-ray absorptiometer (DXA). Body composition was also asse ssed. The kayakers had a significantly (P < 0.05-0.01) greater BMD in most upper body sites: left and right humerus (10.4% and 11.7%), respectively, r ibs (6.4%), spine (10.9%). and a greater BMC of the left and right arm (15. 7% and 10.6%, respectively). No significant differences in the BMD of the t otal body, head, or any of the lower body sites were found, except for the pelvis, which was significantly greater in kayakers (5.1%). The controls ha d a significantly lesser lean body mass (10.4%) and greater percentage of b ody fat (19.5%) than the kayakers. Bivariate correlation analysis in the co ntrols demonstrated significant and strong relationships between BMD in upp er body sites and lean body mass, weight, and fat; the effects of training seem to outweigh most such relationships in kayakers. In conclusion, it see ms that the loading pattern and muscular contractions associated with kayak ing may result in site-specific adaptations of the skeleton.