HIGH THIGH MUSCLE STRENGTH BUT NOT BONE MASS IN YOUNG HORSEBACK-RIDING FEMALES

To evaluate whether the type of weight-bearing loading subjected to th e skeleton during horseback-riding was associated with differences in bone mass and muscle strength of the thigh, we investigated bone mass and isokinetic muscle strength in 20 female horse riders (age 17.9 +/- 0.6 years) who were riding 7.0 +/- 3.4 hours/week, and 20 nonactive f emales (age 17.8 +/- 1.1 years). The groups were matched according to age, weight, and height. Areal bone mineral density was measured in to tal body, head, lumbar spine, right femoral neck, Ward's triangle, and trochanter, the whole dominant and nondominant humerus, and in specif ic sites in the right femur diaphysis, distal femur, praximal tibia, a nd tibia diaphysis using dual X-ray absorptiometry. Isokinetic concent ric and eccentric peak torque of the quadricep and hamstring muscles w ere measured using an isokinetic dynamometer. There were no significan t differences in bone mass between the horseback riders and nonactives at any site measured. The horse riders were significantly (P < 0.05-0 .01) stronger in concentric hamstrings strength at 90 degrees/second a nd 225 degrees/second and in eccentric quadricep and hamstring strengt h at 90 degrees/second. Horseback riding in young females is associate d with a high muscle strength of the thigh, but not with a high bone m ass.