• Iron-deficiency anemia impairs exercise capacity, but whether nonanemic iron depletion decreases endurance performance is unclear. In 14 iron-deficient (serum ferritin level, <20 μg/L [<20 ng/mL]) nonanemic runners, hematologic and treadmill running values were followed up during a competitive season. Following a four-week control period, runners were treated for one month in a double-blind protocol with ferrous sulfate (975 mg/d) or placebo. During treatment, the mean ferritin level rose from 8.7 to 26.6 μg/L (8.7 to 26.6 ng/mL) in those patients taking iron and fell from 10.6 to 8.6 μg/L (10.7 to 8.6 ng/mL) in the placebo group. Treadmill endurance times improved significantly in the iron-treated runners compared with controls. Endurance time declined in all seven controls (range, 0.07 to 1.30 minutes), while six of seven iron-treated subjects improved their performance (range, 0.03 to 1.92 minutes). No significant differences in maximal or submaximal oxygen consumption, ventilation, or heart rate were observed between the groups except for a 4% increase in maximum oxygen consumption during placebo treatment. These data indicate that nonanemic iron deficiency impairs exercise performance but does not influence gas exchange or cardiac measures.
Rowland TW, Deisroth MB, Green GM, Kelleher JF. The Effect of Iron Therapy on the Exercise Capacity of Nonanemic Iron-Deficient Adolescent Runners. Am J Dis Child. 1988;142(2):165-169. doi:10.1001/archpedi.1988.02150020067030