Effects of low ferritin concentration on endurance performance.

To determine the effects of depleted iron stores on endurance performance and blood lactate concentration, eight active women with normal (> 26 ng/ml) and eight with low (< 12 ng/ml) plasma ferritin concentrations were studied while performing a VO2max and an endurance test (80% VO2max) on a cycle ergometer. The low ferritin group had significantly lower serum iron concentration and transferrin saturation and higher TIBC than the normal ferritin group. Mean VO2max was not significantly different between groups. No significant difference was found in total time to exhaustion during the endurance test for low (23.2 min) and normal (27.0 min) ferritin groups; however, the normal ferritin group exercised 14% longer. Blood lactate concentrations following the VO2max and endurance test did not differ significantly between groups. Food diaries revealed lower daily absorbable iron intake by the low ferritin group compared to the normal ferritin group. Ferritin concentration was significantly related to absorbable iron (r = .72) and total iron (r = .70) intake. The results suggest that women with depleted iron stores who are not anemic may have less endurance, but do not have higher blood lactate during exercise than women with normal iron stores.