Effects of iron repletion on VO2max, endurance, and blood lactate in women

To determine the effects of an 8-wk dietary iron supplementation (100 mg.d-1) on low plasma ferritin concentration (< 20 ng.ml-1) and endurance, 20 active women (19-35 yr) were studied while performing a VO2max test and an endurance test (80% VO2max) on a cycle ergometer. Subjects were randomly placed in an iron supplement (IG) or a placebo group (PG) using a double-blind method. After treatment in the IG, ferritin levels were higher (22.5 +/- 3.4 vs 14.3 +/- 2.2 ng.ml-1; P < 0.05), Hb increased (12.8 +/- 0.4 to 14.1 +/- 0.2 g.dl-1; P < 0.05), and TIBC decreased (366.2 +/- 24.8 to 293.8 +/- 14.0 micrograms.dl-1; P < 0.05). Also after treatment the IG's VO2max was significantly greater (P < 0.05) than the PG value and their postendurance blood lactate decreased (5.03 +/- 0.44 to 3.85 +/- 0.6 mM.l-1; P < 0.05). Endurance time to exhaustion increased 38% (37.28 +/- 5.03 to 51.4 +/- 7.45 min) following iron treatment; however, this change was not statistically significant. The results suggest that this level of iron supplementation can reverse mild anemia, increase VO2max, and reduce blood lactate concentration after submaximal exercise.