SITE-SPECIFIC BONE MASS-DIFFERENCES OF THE LOWER-EXTREMITIES IN 17-YEAR-OLD ICE HOCKEY PLAYERS

The purpose of the present study was to evaluate bone mass in the pelv is and lower extremities in young ice hockey players, and especially t o investigate whether any differences are related to the type and magn itude of weight-bearing loading and muscle stress. The ice hockey grou p consisted of 22 boys (mean age 16.9 +/- 0.3) from three different ic e hockey teams training for about 9 hours/week (mean 9.3 +/- 2.0, rang e 6-15). The reference group consisted of 22 boys (age 16.8 +/- 0.3) n ot training for more than 4 hours per week (mean 1.5 +/- 1.5, range 0- 4). The groups were matched according to age, pubertal stage, weight, and height. Areal bone mineral density (BMD) was measured in total bod y, head, pelvis, ala ossis ilii, femoral neck, trochanter, femur diaph ysis, and tibia diaphysis using dual energy X-ray absorptiometry. Isok inetic muscle strength of the quadriceps and hamstrings muscles was me asured using an isokinetic dynamometer. BMDs of the total body, femora l neck, trochanter, and pelvis, but not of the head, ala oasis ilii, f emur diaphysis, and tibia diaphysis, were found to be significantly hi gher (P < 0.05) in the ice hockey group. Muscle strength of the quadri ceps muscles was also found to be significantly higher among the ice h ockey players, but this greater muscle strength did not predict any BM D site significantly. However, in the reference group, there was a gen eral strong relationship between muscle strength and BMD. This study h as demonstrated significantly higher BMD in adolescent ice hockey play ers than in referents on a low or moderate level of physical activity. The differences seem to be site-specific and may be related to the ty pe and magnitude of loading acting on each site, during off-season tra ining and preferentially during ice hockey. The nonsignificant differe nces in BMD of the tibia and femur diaphyses may reflect that the comp ressive forces acting on these sites during ice hockey are not of suff icient magnitude to influence BMD. High muscle stress in itself, witho ut weight-bearing loading, acting on the ala ossis ilii in adolescent boys does not seem to increase BMD, and an increased muscle strength d oes not predict BMD in highly trained adolescent boys.