Effects of a training intervention tailored to the menstrual cycle on endurance performance, recovery and well-being in female recreational runners – A randomized-controlled pilot study
Authors: Kubica Claudia , Ketelhut Sascha , Nigg Claudio R. 
Published: February 2023

Introduction
Female endurance athletes, such as runners, show a high prevalence of menstrual cycle (MC) related symptoms and diseases (Dusek, 2001). Almost one in four runners and 65% of long-distance runners are suffering from secondary amenorrhea (Dusek, 2001) and consecutive symptoms, such as an increased risk of injury, reduced bone mass, and a higher risk for cardiovascular diseases (Ihalainen et al., 2021). Causes for MC-related symptoms or diseases are multifactorial but in sports, a relationship to the training load, recovery, and sufficient energy availability exists (Redman & Loucks, 2005). Evidence is growing that the MC phases affect endurance performance development, training response, and recovery in eumenorrheic women (with normal or regular menstruation), and adaptions of the training program to the MC could reduce risk factors for MC-related symptoms and diseases (Ihalainen et al., 2021; McNulty et al., 2020; Oosthuye & Bosch, 2010). This assumption is based on the changes in steroid hormone concentrations of estrogen and progesterone and their interactions (Pitchers & Elliott-Sale, 2019) during the MC. Five phases usually describe the MC: the early follicular phase, beginning with the onset of menses; the late follicular phase; ovulation; early-, mid-, and late luteal phase (Janse de Jonge et al., 2019). High estrogen levels characterize the late follicular phase and ovulation. In comparison, during the mid-luteal phase, progesterone is the dominating hormone (Janse de Jonge et al., 2019). Current findings in resistance training support the idea that responses to follicular phase-based training are superior to luteal-phase-based or regular training (Thompson et al., 2020). Adaptions of a traditional training program, such as polarized training (Kenneally et al., 2018), to the individual MC phases may impact training response, adaptation, and recovery in female runners (Ihalainen et al., 2021). To our knowledge, no study has investigated the impact of a polarized training intervention tailored to the MC on performance, recovery, and well-being in eumenorrheic women. Therefore, this study aimed to assess the effectiveness of polarized training in female runners and polarized training adaption to the MC phases on endurance performance development, recovery, and MC-related symptoms, as a part of well-being.
Methods
Fourteen eumenorrheic, moderately trained female runners (age: 24 ±2.8 years; BMI: 22.3 ±2.6 kg/cm2; 240 ±152 min of moderate to vigorous physical activity/week) took part in an 8-week running training intervention consisting of three weekly training sessions. The participants were randomly assigned to a control and an intervention group. Menstrual cycles and time points of menstruation and ovulation were determined by calendar-based counting. The control group (CG) followed a general polarized training program (Muñoz et al., 2014) consisting of two 4-week mesocycles. The mesocycles included three weeks of progressive training load and one week with a reduced load, not adjusted to the MC. The intervention group (IG) followed the same training. However, the single training sessions were adapted to their MC with a higher training load within the follicular phase, medium training load within the luteal phase, and regeneration during the premenstrual and menstrual phases. Both interventions were load-matched and controlled by the training impulse (TRIMP) of all training sessions. At baseline and following the intervention period, anthropometrics (weight, height, BMI), performance (countermovement jump performance [CMJ] [OptoGait, MicroGait, Italy], and maximum oxygen uptake [VO2peak {treadmill: Quasar, h/p/cosmos, Germany; respiratory gas analyzer: MetaMax 3B, Cortex, Germany}]) were assessed. The TRIMP and rate of perceived exertion (RPE) were collected to determine training loads for each training session. Furthermore, recovery and well-being were monitored using the short version of the Recovery and Stress Questionnaire (SRSS; recovery subscale: rSRSS; stress subscale: sSRSS) in the baseline assessment and at the end of the training intervention. The premenstrual assessment form (PAF) was used to determine MC-related symptoms at the same time points.
Results
Seven females were each randomly assigned to the IG (age: 22.4 ±1.2; BMI: 22.7 ±2.9 kg/cm2; VO2peak: 41.1 ±4.4 ml/min/kg; CMJ: 26.7 ±6.2; PAF: 23.1 ±8,4; rSRSS: 16.6 ±2.3) and to the CG (age: 24.1 ±3.0; BMI: 21.8 ±2.1 kg/cm2; VO2peak: 43.6 ±6.1 ml/min/kg; CMJ: 27.1 ±5.9 cm; PAF: 25.6 ±5.8; rSRSS: 14.1 ±2.7). No significant group differences were revealed in the baseline assessment for anthropometrics, performance, recovery, and well-being (p < .05).
A repeated measures ANOVA with a Greenhouse-Geisser correction determined no statistically significant time x group interaction effects in mean performance levels (VO2peak: F(1, 6) = 0.21 p = .890 η² = .003; CMJ: F(1,6) = .691 p = .690 η² = .028). Also no significant time x group interactions effects were found for PAF (F[1,6] = .293 p = .608 η² = .047); rSRSS (F[1,6] = .153 p = .709 η² = .0.25) and sSRSS (F[1,6] = .004 p = .952 η² = .0.001).
A significant time effect was found for VO2peak (F[1,6] = 17.93 p = .005 partial η² = .75), but not for the other parameters (p < .05). No group effect was found for any of the parameters (p < .05).
Discussion, conclusion, and research perspective
An 8-week polarized running training, block-periodized or individually adapted to the MC, is efficacious in improving VO2peak in eumenorrheic female runners. These results are in line with previous findings (Muñoz et al., 2014; Stöggl & Sperlich, 2014). Running training adapted to the menstrual cycle seems to impact performance development in an 8-week training intervention to the same extent as traditional block-periodized training. Our results implicate no further benefits of an MC adapted training on recovery and premenstrual symptoms in recreational runners. However, a post-analysis revealed that in 57% of participants in the CG, training recovery phases of the block-periodized training protocol randomly matched with current recommendations for the late-luteal and early-follicular phase of their MC (Pitchers & Elliott-Sale, 2019).Therefore, the structure of the training protocols between the IG and CG did not really differ. Additionally, the less reliable calendar-based determination of the menstrual cycle (Thompson & Han, 2019) limits the generalization of the results and comparability of the IG and CG. Therefore, we are currently conducting a study with a lager sample size and enhanced study design, including determining the menstrual cycle via changes in basal body temperature and luteinizing hormone occurrence. The control group’s training program will be adapted contrary to the current menstrual cycle training recommendations (Pitchers & Elliott-Sale, 2019) to avoid random matches for the recovery phase. Furthermore, questionnaire-based data assessing recovery, well-being, and (pre-)menstrual symptoms using ecologic-momentary assessment and daily heart rate variability measurements will be included to get an in-depth insight into the well-being of the eumenorrheic women. The follow-up study results will be presented at the conference.
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