Effect of iron supplementation on maximal oxygen uptake in female athletes

Background/Aim. Iron is a vital constituent of hemoglobin, myoglobin, and some mitochondrial enzymes; therefore, body iron deficiency may result in reduced aerobic capacity. The aim of this study was to evaluate the effects of daily oral iron supplementation on body iron status, and the maximal oxygen uptake (VO2max) in female athletes with latent iron deficiency, as well as with iron-deficiency anemia. Methods. A total of 37 female volleyball players were included in the study. Seventeen female athletes had latent iron deficiency, and 20 ones iron deficiency anemia. Both groups were divided into the experimental and the control group. The experimental groups received a daily oral iron supplement (200 mg ferrous sulfate), for a two-month training course. Iron status was determined by scrum parameters as follows: red blood cells count, hemoglobin concentration, serum iron and ferritin levels, an unsaturated iron binding capacity, total iron binding capacity and transferrin saturation. VO2max was determined by an indirect test. Results. Statistical difference between the latent iron deficient group versus the iron deficient anemic group was found regarding VO2max (p < 0.001). There were correlations between hemoglobin concentration and VO2max in the latent iron deficient group, as well as in the iron deficient anaemic group (p < 0.05). After two months, there was a significant increase in VO2max in all groups (from 7.0% to 18.2%). Values of VO2max at the end of training period were significantly different (45.98 +/- 1.76 vs 42.40 +/- 1.22 mL/kg/min; p < 0.001) between the experimental and the control group only in female athletes with iron deficiency anemia. After the supplementation, markers of iron status were significantly higher in supplemented groups than in the controls. Conclusion. VO2max was significantly lower in the iron deficient anemic group versus the latent iron deficient group. Iron supplementation during a two-month training period significantly improved body iron status in the iron deficient female athletes with or without anemia, and significantly increased VO2max only in the subjects with iron deficiency anemia.