FREDERICKSON, LUCINDA A., JACQUELINE L. PUHL, and WILLIAM S. RUNYAN. Effects of training on indices of iron status of young female cross-country runners.Med. Set. Sports Exerc., Vol. 15, No. 4, pp. 271–276, 1983. Hematological status and selected indices of iron status were assessed in a group of eight high-school female cross-country runners at weeks 0, 1, 2, 4, and 8 of the competitive season and at 1, 5, and 11 wk after the season. Over the season, a training effect occurred, as was shown by a significant decrease (12.8%) in step-test heart rate and a significant increase (7.0%) in &OV0312;O2max(ml·min-1kg-1). The runners experienced “sports anemia” in that their hemoglobin (Hb) concentration and packed red blood cell volume (FCV) declined significantly during the first week of training (8.8 and 8.3%, respectively), whereas changes did not occur in a comparison group of 11 nonrunners who were followed for the first 3 wk of the season. Between weeks 1 and 8 of the season, the runners' Hb and PCV values gradually returned toward preseason values while their serum iron (SeFe) and percent transferrin saturation (% Sat) showed steady, but nonsignificant, declines, and their total iron-binding capacity (TIBC) rose by 9.4% and continued to rise through the first week after the season. Concomitantly, the runners' free erythrocyte porphyrin (FEP) concentrations rose by 15%. By the end of the detraining period, all indices of iron status had returned to initial values except for TIBC, which still was significantly higher than preseason values. With the exception of TIBC, no significant changes occurred in the iron-status indices of the comparison group during the 2 wk they were followed. The results suggest that in young women recovery from sports anemia may impose a demand on body iron reserves and that it would be prudent to assess iron status as well as hematological status in such women before and during aerobic training.