The female athlete—reliability of body composition analyses during the female menstrual cycle in young women without hormonal contraception

The menstrual cycle (MC) is characterized by rapid changes of female sexual hormone concentrations with consecutive water retention alterations, which in turn might affect underlying parameters of body composition (BC) analyses in terms of air-displacement plethysmography (ADP) or bioelectrical impedance analysis (BIA).

The purpose of this study was to evaluate BC and the assessment’s reproducibility and reliability during the MC.

In a repeated measures design with four time points (t1–t4) and a double testing within 10 min at t1 (t1.1–t1.2) covering a complete MC (t1.1: start of menstruation [t1.2: double testing], t2: late follicular, t3: ovulation, t4: mid-luteal), 17 eumenorrheic women without hormonal contraception (age: 24.8 [18.5–33.1] years, body mass index [BMI]: 23.3 [18.0–27.8] kg/m²) were examined by means of ADP (BODPOD GS‑X, Cosmed, Rome, Italy) and BIA (mBCA 515/514, Seca, Hamburg, Germany) in order to determine reliability (intraclass correlation [ICC_2.1]) and within-subjects variability (standard error of the measurement [SEM], minimal detectable change [MDC], coefficient of variation [CV%]) covering the complete MC (t1–t4).

The CV% showed small variations ranging between 0.8 and 2.7%, except for the BIA reactance (4.2%). Reliability was excellent (ICC_2.1 > 0.9) for all BC parameters and all intervals (t1.1 vs. t1.2, t2, t3, and t4, respectively), except for the reactance (0.7 > ICC_2.1 > 0.55).

Reproducibility and reliability of BC analyses were not influenced by the MC. Thus, BC of female athletes may be determined irrespective of the phase of their MC. Future research might cover more than one MC or consider women with hormonal contraception or males serving as controls.