Endurance athletes are always looking for a competitive edge; that is why we put so much time and energy in to proper training and state-of-the-art equipment. For those who are serious about their performance (or, more importantly, are serious about their health), you may want to look beyond heart rate data, swim splits, and power numbers. Specifically, you may want to have your iron levels tested.
A study published in the International Journal of Sport Nutrition and Exercise Metabolism reported that rowers who show signs of iron depletion without anemia at the beginning of a training season perform poorer during 2-km time trials than those with a normal iron status; specifically 21 seconds slower on average!
While these findings may be intuitive to some, recent estimations have conclude that 25-44% of female runners as well as 4-13% of male endurance athletes are iron-deficient. Therefore, many athletes may unknowingly be iron-deficient without overt signs of anemia; an effect which (according to the cited research article) can present through impairments in optimal performance.
Hence, this study highlights: a) the importance of knowing one’s iron status prior to and/or during a training season; and b) determining whether an athlete could potentially benefit from iron supplementation.
With regard to research examining iron supplementation, iron-deficient subjects who were supplemented over an 80-day period experienced a 61-97% increase in blood hemoglobin, a reduction in peak exercise heart rates from ~150 beats per minute to ~120 beats per minute (signifying less fatigue), a 15% increase in oxygen delivery to working muscles during exercise, and a significant reduction (~50%) in blood lactate levels immediately after exercise (signifying less fatigue). Indices of iron status can be acquired through blood testing at a general physician’s office and typical iron supplementation regimens include consuming 100-975 mg/day of ferrous sulfate.
NOTE: You should not begin iron supplementation unless it is suggested by a doctor. The only way to find out if iron supplementation is necessary is to have your iron levels checked. Too much iron can lead to health issues.
DellaValle DM, Haas JD. Impact of iron depletion without anemia on performance in trained endurance athletes at the beginning of a training season: a study of female collegiate rowers. Int J Sport Nutr Exerc Metab. 2011 Dec;21(6):501-6.
Lukaski, HC, Vitamin and mineral status: effects on physical performance. Nutrition, 2004. 20(7-8): 632-44.
Gardner, G., et al., Cardiorespiratory, hematological and physical performance responses of anemic subjects to iron treatment. Am J Clin Nutr, 1975. 28(9): 982-8.