I found this interesting article by a high school track coach. He found ferritin depletion common among his athletes, particularly girls.
Very interesting to me. I've been running half marathon distances and have a ferritin level of 22.Iron is lost through sweat and gastrointestinal irritation. It is temporarily lost through "footstrike hemolysis" (bursting blood cells through foot impact with the ground). ... While iron depletion rarely results in the general lethargy associated with true iron-deficiency anemia, distance runners with low ferritin will likely experience abnormal exhaustion, increased blood lactate, slow recovery, declining performances, heavy legs, muscular tightness, loss of motivation, and substantially increased risk of injury ...
Overuse injuries (the type of injuries distance runners get) double with ferritin levels under 20 and triple with levels under 12. I think it's safe to suggest that iron depletion is rarely considered to be the root cause of these injuries. Instead we focus on mileage, running surfaces, shoes and the other usual suspects. If you were nodding your head thinking the previous symptoms sound like a checklist of your most recent season, go get your serum ferritin tested.
StephenB