Introduction:
One possible way of iron loss is sweating. It is unclear how physical activity performed by untrained individuals affects the iron status in sweat.

Objective:
The purpose of this study was to analyse iron concentration in sweat during 4-week exercise training to determine the changes in iron excretion during follow-up exercises.

Material and methods:
43 untrained volunteers participated in the study, 29 of whom completed the full exercise programme. The training programme consisted of exercises on a cycle ergometer and cross-trainer. In the first week, participants exercised for 8 minutes on each device, in the second for 10 minutes, and in the third and fourth weeks they exercised for 15 min on each device. Intensity was submaximal and defined as 85% of maximal heart rate. A sterile sweat patch was placed on the skin between shoulder blades.

Results:
Concentration of iron on the first and the fifteenth day of exercises was comparable and statistically insignificant. Iron concentration was highly increased on the last day of training in comparison with first (p<0.001) and fourteenth day (p<0.006). The median of iron concentration in 29 samples on the first day of sampling was 21.2 ppb, in the fifteenth – 52.5 ppb, and on the twenty-eighth day – 286.2 ppb. In relation with the sodium concentration, the iron content was also increased on the twenty-eighth day of the training programme (p<0.005).

Conclusions:
Iron sweat loss significantly increased during the 4-week exercise programme. A possible explanation may be improvement in the thermoregulation mechanism and secretory activity of sweat glands. Iron sweat loss may be an indicator of iron deficiency observed in active individuals.