Do sweat calcium losses affect bone mass during firefighter training?

Although participation in vigorous exercise is associated with increased bo ne mass, recent evidence suggests that loss of calcium in sweat may result in a negative calcium balance and ultimately, a decrease in bone mass. Anth ropometric characteristics, habitual physical activity levels, dietary calc ium intake, bone mineral content, and bone turnover markers were measured i n 42 male recruits before and after 4 months of firefighter training During two strenuous mid-training sessions, sweat calcium concentrations were mea sured; they averaged 1.1 mM. Whole body and total hip bone mineral content increased significantly, as did one marker of bone formation, and were not associated with sweat calcium concentration This study demonstrates that in tense physical training sessions that produce high sweat rates do not have an adverse effect on the bone mineral content of healthy young men.