Purpose: Studies in animals and humans show a link between iron depletion without anemia (IDNA) and physical performance. Consequences of IDNA relevant to athletes include reduced endurance and energetic efficiency. We conducted this cross-sectional study to investigate the relationships between iron status, performance, and training in nonanemic female rowers.
Methods: Iron status (hemoglobin, serum ferritin, soluble transferrin receptor) of 165 rowers was assessed at the beginning of a training season; 27% (n = 44) of rowers were identified as IDNA (serum ferritin < 20.0 μg·L) and 10% as anemic (n = 16, hemoglobin < 12.0 g·dL). Physical performance of 48 nonanemic rowers (n = 24 normal, n = 24 depleted) was assessed (V˙O(2peak), 4-km time, gross energetic efficiency), and training was recorded. Daily training load was calculated using the session RPE method (training duration × intensity rating).
Results: There were no significant differences between the two groups of iron status in any of the potential confounders of the association between iron status and performance that were tested. Compared with rowers with normal iron status, rowers with depleted iron trained ∼10 min less per day (P = 0.02) and had a 0.3-L·min lower V˙O(2peak) (P = 0.03). Both serum ferritin and training group (high vs low based on a session RPE of 3200) were positively related to V˙O(2peak). Less highly trained rowers with poor iron status had a lower V˙O(2peak) (-0.32 L·min, P = 0.02) and were less energetically efficient (-1.7%, P = 0.09) compared with more highly trained rowers with poor iron status.
Conclusions: Impaired iron status is a prevalent problem among female endurance athletes. The relationship between rowers' iron status and endurance performance varied depending on training load. IDNA may prevent rowers from training as hard, directly affecting their performance.