Iron and Muscular Damage: FEmale Metabolism and Menstrual Cycle During Exercise

Iron and Muscular Damage: FEmale Metabolism and Menstrual Cycle During Exercise

This project is an observational controlled randomized counterbalance study. One hundred and three physically active and healthy women were selected to participate in the IronFEMME Study, of which 57 were eumenorrheic, 30 were oral contraceptive users (OCP) and 16 were postmenopausal women. The project consisted on two sections carrying out at the same time: Iron metabolism (Study I) and Muscle damage (Study II). For the study I, the exercise protocol consisted on an interval running test (8 bouts of 3 min at 85% of the maximal aerobic speed), whereas the study II protocol was based on an eccentric-based resistance exercise protocol (10 sets of 10 repetitions of plate-loaded barbell parallel back squats at 60% of their 1RM with 2 min of rest between sets). In both studies, eumenorrheic participants were evaluated at three specific moments of the menstrual cycle: Early-follicular phase, late-follicular phase and mid-luteal phase; OCP performed the trial at two moments: Withdrawal phase and active pill phase. Lastly, postmenopausal women were tested only once, since their hormonal status does not fluctuate. The three-step method was used to verify the menstrual cycle phase: calendar counting, blood analyses confirmation and urine-based ovulation kits. Blood samples were obtained to measure sexual hormones (e.g., 17β-Estradiol, Progesterone), iron metabolism parameters (e.g., Hepcidin, Iron, Ferritin, Transferrin) and muscle damage related markers (e.g., Creatine Kinase, Myoglobin, Lactate Dehydrogenase).

Inclusion Criteria:

Participants were required to meet the following criteria:

• Healthy adult females between 18 and 40 years old for eumerroheic and oral contraceptive groups or under 60 years old for postmenopausal women.
• Presenting with healthy iron parameters (serum ferritin >20μg/l, haemoglobin >115 μg/l and transferrin saturation >16%).
• Performing endurance training between 5 and 12 h per week (study I) or experienced in resistance training performing at least 1 h session two times per week during a minimum of a year (study II).

Exclusion Criteria:

The exclusion criteria included:

• Irregular menstrual cycles.
• Any existing disease and/or metabolic or hormonal disorder.
• Any musculoskeletal injury in the last six months prior to the beginning of the project.
• Any surgery interventions (e.g. ovariectomy) or other medical conditions that would be exacerbated by an eccentric resistance exercise protocol.
• Regular use of medication or dietary supplements that could affect the results (e.g. nonsteroidal anti-inflammatory drugs).
• Taking medication that alters vascular function (e.g. tricyclic antidepressants, α-blockers, β-blockers, etc.).
• Pregnancies in the year preceding.
• Smoking.