More days of either aerobic or strength exercise were associated with higher levels of iron and percent saturation in both men and women. In addition to being important for the production of hemoglobin and new red blood cells, iron is an important constituent of myoglobin and various enzymes. Iron is also important to the metabolic processes involved in exercise and adaptations to exercise training . Athletes may lose iron 20% faster than non-athletes , as iron red blood cells are broken down during exercise by the mechanical stress of muscle contraction . Thus, the higher levels of iron and percent saturation in those with higher activity levels may be due to increased needs for iron during exercise .