The effect of intense physical training on the bone-mineral content of
young adults who are unaccustomed to physical activity has not yet been
established. In this study, 268 male recruits, eighteen to twenty-one years
old, were evaluated before and after fourteen weeks of strenuous physical
training. The bone-mineral content of both legs at the level of the distal
third of the tibia in each individual was measured using single-beam photon
absorptiometry. The subjects started their training with equal values for
bone-mineral content in both legs. During the training period, the average
bone-mineral content of the left leg increased by 11.1 per cent and that of
the right leg, by 5.2 per cent. In the group of subjects who did not
complete the training course, mainly because they incurred stress
fractures, the increase in bone-mineral content was significantly less than
the increase in those who completed the program. This study indicated that
in young adults a high level of loading of bone results in either a stress
fracture or a rapid increase in bone-mineral content.