Abstract
Iron plays a fundamental role in biochemical processes underpinning key physical capacities required for sports performance. Athletes, particularly regularly menstruating biological females, are predisposed to biological, lifestyle, and environmental factors that exacerbate iron losses. Team sport athletes often need a combination of physical attributes, including aerobic endurance, muscular strength and power, speed, and the ability to perform repeated sprints. However, the effects of iron deficiency on a diverse suite of physical capacities beyond endurance performance and maximal aerobic capacity remain largely unexplored. This doctoral thesis aimed to 1) identify the iron knowledge of female athletes and affiliated sport science staff, 2) explore the factors underpinning the categorisation and treatment of iron deficiency in athletes by dietitians and iron experts, and 3) assess variations in seasonal iron and vitamin D concentrations, and how iron deficiency impacts physical performance measures in team sport athletes.A systematic review on iron and female athletic performance reported that iron deficiency can impair endurance capacity, reduce energy efficiency, lower maximal work rates or velocities, and alter blood lactate levels. However oral iron supplementation (FeSup; ≤100 mg/day of elemental iron for ≤56 days) can improve these outcomes. Reductions in maximal aerobic capacity appear to align with the severity of iron deficiency, whereas strength performance showed a more variable response. A cross-sectional study using a two-part web-based questionnaire assessing iron-related knowledge in athletes and key support staff (e.g., strength and conditioning coaches, physiotherapists, and performance analysts) found that iron knowledge scores ranged between 21% to 88% for female athletes (46% ± 13%; mean ± SD) and key staff (60% ± 16%; p=0.002). Among dietitians and iron experts, up to 56% of them applied widely ranging established diagnostic criteria for iron deficiency, with FeSup protocols varying up to five-fold for early-stage deficiency and three-fold for anaemia.
Two prospective longitudinal studies across the 2023 National Rugby League Women’s (NRLW) and 2024 Australian Football League Women’s (AFLW) seasons established iron deficiency (sFer <40 μg/L) prevalence peaked at ~55% in both teams occurring at the start of pre-season in NRLW players and at the end of the season in AFLW players. Differences in external load measures between iron deficient (ID) and iron sufficient players were mainly trivial to small, with stronger contributions from moderating variables playing position and change in weekly training loads. Heightened iron status (players who reported unmeasured iron supplementation) had an inconsistent association on external load (e.g., total distance, highspeed running) and strength and power measures (e.g., countermovement jump, Nordic hamstring curl) in AFLW players with performance changes ranging between -47% to +19% between the end of preseason (week 10) and end of season (week 24). Strength and power performance (bench press, squat, hip thrust, countermovement jump) declined by up to 15% in ID AFLW players throughout the preseason, while sprinting performance (maximal velocity and 10-m sprint) declined by 1% to 2%.
Iron deficiency is as prevalent in team sport athletes as it is in endurance athletes. However, factors such as player position and weekly training load fluctuations appear to have a greater impact on external load performance than serum ferritin concentration. Compound strength (e.g., bench press, squat, hip thrust) performance appears to be affected by iron status, but not strength and power measures typically employed to screen injury risks and limb asymmetries (e.g., Nordic hamstring curl, hip adduction). Routine iron monitoring (e.g., quarterly or biannually if feasible) is essential in female team sports to mitigate potential performance decrements and adverse health outcomes.
| Date of Award | 2025 |
|---|---|
| Original language | English |
| Supervisor | Naroa ETXEBARRIA (Supervisor) & Kate PUMPA (Supervisor) |