How Does Iron Supplementation Affect Training and Performance in Female Collegiate Rowers?
Condition: Iron Deficiency (Without Anemia)
MeSH terms: Anemia; Anemia, Iron-Deficiency; Iron Deficiencies
Study type: Interventional

Summary: 
      The specific aims of the current study were: 1) To determine the prevalence of IDNA in a
      sample of female rowers at the beginning of a training season; 2) To determine how IDNA
      affects endurance training and performance at the beginning of a training season; 3) To
      determine how iron supplementation affects iron status, training and performance in IDNA
      female collegiate rowers. The researchers hypothesized that IDNA affects endurance
      performance in female collegiate rowers both in and outside of the laboratory, and that iron
      supplementation of IDNA rowers will improve iron status, and consequently, training quality
      via increased energetic efficiency.
    

Detailed description: 
      Iron deficiency (ID) is the most common nutrient deficiency in the United States, affecting
      13% of pre-menopausal women, and approximately 30% of physically-active women (1, 2). Iron
      deficiency anemia (IDA) is clinically defined as hemoglobin (Hgb) less than 12.0 g/dl. Iron
      depletion without anemia (IDNA), or low iron stores, is defined as Hgb greater than 12.0 g/dl
      and serum ferritin (sFer) less than 20.0 µg/L. Female athletes are at higher risk of IDNA due
      to their menstrual status, poor dietary intake, and high training volume and intensity (3).
      Consequences of IDNA that may be relevant to athletes include reduced work capacity,
      endurance, and energetic efficiency (4-6); and increased local muscle fatigue (7). The
      mechanism by which IDNA affects endurance and physical performance remains unclear, and the
      functional consequences of IDNA are not fully understood in trained individuals, as studies
      to examine these relationships have been underpowered (8, 9).

      Our lab has previously reported the effects of iron deficiency on physical performance in
      untrained, IDNA women adapting to an aerobic training program. Hinton et al (5) showed that
      the effect of iron supplementation on physical performance was mediated by changes in iron
      status (sFer), and concluded that IDNA reduces the potential benefits of aerobic training on
      endurance. In that study, subjects who were supplemented with iron for 6 weeks during aerobic
      training improved their time to complete a 15-km cycling time trial by 3.4 min compared to
      1.6 min in the placebo group (p<0.05). Given these convincing results, the study of
      highly-trained competitive female athletes training at a high volume and intensity was
      warranted. We expected these significant effects to persist in competitive collegiate
      athletes. However, we expected the magnitude of these effects to be somewhat less due to
      collegiate athletes' advanced training status, and thus a smaller margin of improvement in
      performance due to response of increased body iron stores. The goal of the proposed study was
      to determine whether marginal iron deficiency (IDNA) impairs the ability of moderately- to
      highly-trained female collegiate rowers to increase their training quality, as well as their
      performance in response to 6 weeks of iron supplementation, in addition to their usual
      endurance training.

      This study was conducted in three phases. Phase 1 was a cross-sectional study designed to
      describe the iron status of a diverse sample of female collegiate rowers around central New
      York state. Iron status was screened with a venous blood sample, and demographic and other
      health and self-reported performance data were also collected. One-hundred and sixty-five
      female collegiate endurance athletes were screened to identify IDNA subjects (sFer <20 µg/l,
      Hgb >12 g/dL) for an iron supplementation trial.

      Phase 2 was a cross-sectional study designed to measure and compare the metabolic and
      functional consequences of ID in a sample of highly-trained female rowers across a broad
      range of both fitness levels (novice to varsity)and iron status (normal, ID, and IDNA). This
      cross-sectional study was an analysis of the baseline data for potential RCT participants
      (IDNA) at the beginning of a training season. In addition to those IDNA subjects
      participating in the supplementation trial, we included a sample of non-anemic, non-iron
      deficient rowers. These subjects completed all baseline protocols in the lab, and recorded
      one week of training activities, in addition to all other baseline data collected. This
      cross-sectional study enabled us to investigate potential relationships between iron status
      and early training season performance.

      This plausibility analysis was useful, in light of the putative mechanisms (correlations
      between iron status and physical performance), to explain how iron status may affect physical
      performance. These analyses suggested relationships between iron status and performance, but
      did not provide strong causal evidence, as temporal relationships between iron status and
      performance cannot be determined in a cross-sectional study. We did, however, need to
      identify and control confounding factors related to both iron status and performance to
      control bias.

      Phase 3 was a randomized, placebo-controlled supplementation trial designed to explore how
      IDNA and iron supplementation affect iron status, performance, and training over 6-weeks of
      rowing training. Rowers with normal iron status were included in this study to examine
      training effects (if any) on iron status and performance. This study was designed to
      elucidate the cause-effect relationship(s) between iron status (and iron supplementation),
      training and performance.
    

Intervention name(s): Placebo; Ferrous sulfate
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): 100 mg lactose per day for 6 weeks; 100 mg per day of ferrous sulfate for 6 weeks
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: iron deficiency, physical performance, female athletes