Iron plays a significant role in the body, and is specifically important to athletes, since it is a dominant feature in processes such as oxygen transport and energy metabolism. Despite its importance, athlete populations, especially females and endurance athletes, are commonly diagnosed with iron deficiency, suggesting an association between sport performance and iron regulation. Although iron deficiency is most common in female athletes (~15-35% athlete cohorts deficient), approximately 5-11% of male athlete cohorts also present with this issue. Furthermore, interest has grown in the mechanisms that influence iron absorption in athletes over the last decade, with the link between iron regulation and exercise becoming a research focus. Specifically, exercise-induced increases in the master iron regulatory hormone, hepcidin, has been highlighted as a contributing factor towards altered iron metabolism in athletes. To date, a plethora of research has been conducted, including investigation into the impact that sex hormones, diet (e.g. macronutrient manipulation), training and environmental stress (e.g. hypoxia due to altitude training) have on an athlete's iron status, with numerous recommendations proposed for consideration. This review summarises the current state of research with respect to the aforementioned factors, drawing conclusions and recommendations for future work.

This study explored the relationship between serum ferritin and hepcidin in athletes. Baseline serum ferritin levels of 54 athletes from the control trial of five investigations conducted in our laboratory were considered; athletes were grouped according to values <30 μg/L (SF<30), 30–50 μg/L (SF30–50), 50–100 μg/L (SF50–100), or >100 μg/L (SF>100). Data pooling resulted in each athlete completing one of five running sessions: (1) 8×3 min at 85% vVO2peak; (2) 5×4 min at 90% vVO2peak; (3) 90 min continuous at 75% vVO2peak; (4) 40 min continuous at 75% vVO2peak; (5) 40 min continuous at 65% vVO2peak. Athletes from each running session were represented amongst all four groups; hence, the mean exercise duration and intensity were not different (p>0.05). Venous blood samples were collected pre-, post- and 3 h post-exercise, and were analysed for serum ferritin, iron, interleukin-6 (IL-6) and hepcidin-25. Baseline and post-exercise serum ferritin levels were different between groups (p<0.05). There were no group differences for pre- or post-exercise serum iron or IL-6 (p>0.05). Post-exercise IL-6 was significantly elevated compared to baseline within each group (p<0.05). Pre- and 3 h post-exercise hepcidin-25 was sequentially greater as the groups baseline serum ferritin levels increased (p<0.05). However, post-exercise hepcidin levels were only significantly elevated in three groups (SF30–50, SF50–100, and SF>100; p<0.05). An athlete's iron stores may dictate the baseline hepcidin levels and the magnitude of post-exercise hepcidin response. Low iron stores suppressed post-exercise hepcidin, seemingly overriding any inflammatory-driven increases.

Measuring pretraining subjective wellness may provide information about players' capacity to perform in a training session and could be a key determinant of their response to the imposed training demands American college football. Hence, monitoring subjective wellness may aid in the individualization of training prescription in American college football players.

This study investigated the effect of regular postexercise cold water immersion (CWI) on muscle aerobic adaptations to endurance training. Eight males performed 3 sessions/wk of endurance training for 4 wk. Following each session, subjects immersed one leg in a cold water bath (10°C; COLD) for 15 min, while the contralateral leg served as a control (CON). Muscle biopsies were obtained from vastus lateralis of both CON and COLD legs prior to training and 48 h following the last training session. Samples were analyzed for signaling kinases: p38 MAPK and AMPK, peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), enzyme activities indicative of mitochondrial biogenesis, and protein subunits representative of respiratory chain complexes I-V. Following training, subjects' peak oxygen uptake and running velocity were improved by 5.9% and 6.2%, respectively (P < 0.05). Repeated CWI resulted in higher total AMPK, phosphorylated AMPK, phosphorylated acetyl-CoA carboxylase, β-3-hydroxyacyl-CoA-dehydrogenase and the protein subunits representative of complex I and III (P < 0.05). Moreover, large effect sizes (Cohen's d > 0.8) were noted with changes in protein content of p38 (d = 1.02, P = 0.064), PGC-1α (d = 0.99, P = 0.079), and peroxisome proliferator-activated receptor α (d = 0.93, P = 0.10) in COLD compared with CON. No differences between conditions were observed in the representative protein subunits of respiratory complexes II, IV, and V and in the activities of several mitochondrial enzymes (P > 0.05). These findings indicate that regular CWI enhances p38, AMPK, and possibly mitochondrial biogenesis.

PurposeTo investigate the influence of daily oral iron supplementation on changes in hemoglobin mass (Hbmass) and iron parameters after 2–4 weeks of moderate altitude exposure.MethodsHematological data collected from 178 athletes (98 males, 80 females) exposed to moderate altitude (1,350–3,000 m) were analysed using linear regression to determine how altitude exposure combined with oral iron supplementation influenced Hbmass, total iron incorporation (TII) and blood iron parameters [ferritin and transferrin saturation (TSAT)].ResultsAltitude exposure (mean ± s: 21 ± 3 days) increased Hbmass by 1.1% [-0.4, 2.6], 3.3% [1.7, 4.8], and 4.0% [2.0, 6.1] from pre-altitude levels in athletes who ingested nil, 105 mg and 210 mg respectively, of oral iron supplement daily. Serum ferritin levels decreased by -33.2% [-46.9, -15.9] and 13.8% [-32.2, 9.7] from pre-altitude levels in athletes who supplemented with nil and 105 mg of oral iron supplement daily, but increased by 36.8% [1.3, 84.8] in athletes supplemented with 210 mg of oral iron daily. Finally, athletes who ingested either 105 mg or 210 mg of oral iron supplement daily had a greater TII compared with non-supplemented athletes (0 versus 105 mg: effect size (d) = -1.88 [-2.56, -1.17]; 0 versus 210 mg: effect size (d) = -2.87 [-3.88, -1.66]).ConclusionOral iron supplementation during 2–4 weeks of moderate altitude exposure may enhance Hbmass production and assist the maintenance of iron balance in some athletes with low pre-altitude iron stores.