 To address Aims 1 and 2, the investigators will compare energetic efficiency, maximum ability to use oxygen, ventilatory threshold, and blood lactate concentrations at baseline, after supplementation or placebo, and after exercise training or no training. The 3x2 study design will allow for the determination of whether subjects receiving iron benefit more from exercise training. The investigators will also examine whether participating in exercise training affects iron homeostasis or lowers iron status. 