In the present study, hypothesis that short-term exercise may ameliorate the decrease in bone mass observed with confinement was investigated with horses weaned at 4 months of age and placed into box stalls. After 5 weeks adjustment period horses were then divided randomly into three treatment groups: 1) group housed; 2) confined with no exercise; and 3) confined with exercise. The confined and exercised groups were housed in box stalls for the 56-day duration of the trial. The exercised group was sprinted 82 m/day, 5 days/week, in a fenced grass alleyway. The group horses were housed together in a 992-m2 drylot with free access to exercise. On days 0, 28, and 56, dorsopalmar and lateromedial radio-graphs of the left third metacarpal bone were taken to estimate changes in bone mineral content and cortical widths. The overall results of this study indicate that a short-duration exercise protocol might be effective in improving bone mass and therefore skeletal strength in horses.