Sweat iron loss of male and female runners during exercise

Male (n = 9) and female (n = 8) collegiate cross-country runners were studied during a training session to determine the amount of iron lost in the sweat. Sweat samples were collected from the arm using polyethylene bags. Total sweat loss was determined by weighing subjects before and after the runs. Average time of sweat collection was 42 min for males and 39 min for females. Sweat rate for the males (717.5 +/- 145.9 g/m2/h) was significantly greater than for the females (460.1 +/- 142.9 g/m2/h); however, the sweat rate per km was not significantly different. Females had a significantly greater sweat iron concentration (0.417 +/- 0.024 mg/l) than males (0.179 +/- 0.011 mg/l). Rate of sweat iron loss was not significantly different for females (0.276 +/- 0.140 mg/h) and males (0.21 +/- 0.13 mg/h). Sweat iron concentration was inversely related with sweat rate (r = -0.64). Our data suggest that although males lose more total sweat than females, the higher sweat iron concentration of females leads to similar rates of iron loss. For female runners, sweat iron loss coupled with a low dietary iron intake may result in a negative iron balance.