Four weeks of IV iron supplementation reduces perceived fatigue and mood disturbance in distance runners.

PURPOSE: To determine the effect of intravenous iron supplementation on performance, fatigue and overall mood in runners without clinical iron deficiency. METHODS: Fourteen distance runners with serum ferritin 30-100 µg · L(-1) were randomly assigned to receive three blinded injections of intravenous ferric-carboxymaltose (2 ml, 100 mg, IRON) or normal saline (PLACEBO) over four weeks (weeks 0, 2, 4). Athletes performed a 3,000 m time trial and 10 × 400 m monitored training session on consecutive days at week 0 and again following each injection. Hemoglobin mass (Hbmass) was assessed via carbon monoxide rebreathing at weeks 0 and 6. Fatigue and mood were determined bi-weekly until week 6 via Total Fatigue Score (TFS) and Total Mood Disturbance (TMD) using the Brief Fatigue Inventory and Brunel Mood Scale. Data were analyzed using magnitude-based inferences, based on the unequal variances t-statistic and Cohen's Effect sizes (ES). RESULTS: Serum ferritin increased in IRON only (Week 0: 62.8 ± 21.9, Week 4: 128.1 ± 46.6 µg · L(-1); p = 0.002) and remained elevated two weeks after the final injection (127.0 ± 66.3 µg · L(-1), p = 0.01), without significant changes in Hbmass. Supplementation had a moderate effect on TMD of IRON (ES -0.77) with scores at week 6 lower than PLACEBO (ES -1.58, p = 0.02). Similarly, at week 6, TFS was significantly improved in IRON vs. PLACEBO (ES -1.54, p = 0.05). There were no significant improvements in 3,000 m time in either group (Week 0 vs. Week 4; Iron: 625.6 ± 55.5 s vs. 625.4 ± 52.7 s; PLACEBO: 624.8 ± 47.2 s vs. 639.1 ± 59.7 s); but IRON reduced their average time for the 10 × 400 m training session at week 2 (Week 0: 78.0 ± 6.6 s, Week 2: 77.2 ± 6.3; ES-0.20, p = 0.004). CONCLUSION: During 6 weeks of training, intravenous iron supplementation improved perceived fatigue and mood of trained athletes with no clinical iron deficiency, without concurrent improvements in oxygen transport capacity or performance.

Intravenous iron supplementation in distance runners with low or suboptimal ferritin.

PURPOSE: Iron deficiency is prevalent in distance runners and may impair endurance performance. The current practice of oral supplementation is slow and often not well tolerated. The aim of this study was to assess the efficacy of intravenous (IV) iron supplementation (ferric carboxymaltose) compared with oral supplementation (ferrous sulfate) on iron status, hemoglobin mass (Hbmass), and physiological indices of running performance in distance runners. METHODS: Twenty-seven highly trained distance runners with low (LOW) (ferritin <35 µg·L(-1) and transferrin saturation <20%, or ferritin <15 µg·L(-1)) or suboptimal (SUB) iron status (ferritin <65 µg·L(-1)) were supplemented with either IV iron (Ferinject®) or oral (ORAL) supplements (Ferrogradumet) for 6 wk. Iron status and Hbmass were assessed before supplementation and at 1, 2, 4, 6, and 8 wk in the four groups (IV LOW, IV SUB, ORAL LOW, and ORAL SUB). In addition, athletes completed a treadmill running test for running economy, lactate threshold, and V˙O2max before and after supplementation. RESULTS: Both forms of supplementation substantially increased ferritin levels in all four groups. IV supplementation resulted in higher ferritin in both IV groups compared with both ORAL groups from week 1 onward. Hemoglobin concentration did not change substantially in any group. Hbmass increased in IV LOW (mean = +4.9%, 90% confidence interval [CI] = 1.1%-8.9%) and was accompanied by an increase in V˙O2max (mean = +3.3%, 90% CI = 0.4%-6.3%) and run time to exhaustion (mean = +9.3%, 90% CI = 0.9%-18.3%. CONCLUSIONS: IV supplementation can effectively increase iron stores in iron-deficient runners within 6 wk and, if Hbmass is compromised, may enhance endurance capacity by facilitating erythropoiesis. Hbmass appears a more sensitive tool for measuring changes in whole body hemoglobin than hemoglobin concentration and may be useful in the diagnosis and follow-up for iron deficiency.

Response of soluble transferrin receptor and iron-related parameters to iron supplementation in elite, iron-depleted, nonanemic female athletes.

OBJECTIVES: To assess the effect of short-term iron supplementation on soluble transferrin receptor (sTfR) and the soluble transferrin receptor/log ferritin ratio in a group of elite, iron-depleted, nonanemic female athletes and to assess the relationship between soluble transferrin receptor and serum ferritin in a group of elite, iron-depleted female athletes. DESIGN: A prospective, interventional study and an observation at 1 point in time. The primary inclusion criteria for each component of the study was serum ferritin less than 30 ng/mL and hemoglobin greater than 12 g/dL. The exclusion criteria were use of iron supplementation within 1 month of the initial assessment, acute or chronic infectious or inflammatory disease, hematological disorders, and recent musculoskeletal injury. SETTING: The Department of Sports Medicine at the Australian Institute of Sport. SUBJECTS: For the prospective study, 51, and for the observational study, 85 elite, iron-depleted (serum ferritin <30 ng/mL), nonanemic (hemoglobin <12 g/dL for the prospective study only) female athletes. Athletes were participants at the elite level in netball, basketball, gymnastics, rowing, volleyball, track and field, soccer, sailing, and cricket. INTERVENTION: Ingestion of 1 iron tablet (325 mg dried ferrous sulfate, equivalent to 105 mg elemental iron) plus one 500-mg tablet of vitamin C each morning for 60 days. RESULTS: Following supplementation, the following changes were statistically significant. Serum ferritin increased (19.7 to 37.4 ng/mL; P < 0.00005), serum transferrin decreased (3.34 to 3.16 g/L; P = 0.023), sTfR decreased (3.46 to 3.16 mg/L; P = 0.006), and sTfR/log ferritin index decreased (1.34 to 1.00; P < 0.00005). If it is assumed that iron stores are depleted when serum ferritin is less than 12 ng/mL and that sTfR could be expected to be elevated below that level of serum ferritin, the following figures can be calculated for the value of sTfR in relation to absent iron stores: sensitivity, 33%; specificity, 96%; positive predictive value, 50%; and negative predictive value, 92%. CONCLUSIONS: Short-term iron supplementation increases iron stores and leads to reductions in sTfR and the sTfR/log ferritin index in elite female athletes. sTfR is not an accurate predictor of serum ferritin less than 12 ng/mL in this group.