The influence of the menstrual cycle phase on single-legged balance and jump tests in female football players

Introduction: The different hormonal levels during the female menstrual cycle phases could negatively influence the athletic performance of female athletes, especially during the first (follicular) than the second (luteal) phase. Consequently, this can increase the susceptibility to lower extremity injuries such as anterior cruciate ligament (ACL). [McNulty et al., 2020; Cesar et al., 2011; Hewett et al., 2007] The ability of single-leg balance or jumping are fundamental variables in order to succeed in professional and amateur sports. [Bloch et al., 2019] In addition, single-leg functional performance deficits and interlimb asymmetries during balance or jumping tests have been widely used in literature as lower extremities injury risk factors as well as rehabilitation criteria after ACL injury. [Wilke et al., 2021; Nae et al., 2017] Interlimb asymmetries (Limb Symmetry Index, LSI < 90%) of the lower extremities during the YBT and SLJ have been associated with increased injury susceptibility and unsuccessful rehabilitation. [Wellsandt et al., 2017] In addition, insufficient results in the Y-Balance Test (YBT, Score < 94%) or Single-Leg Jump for Distance Test (SLJ, Score < 70% of body height) might place female athletes at higher risk of lower extremities injuries. [Bloch et al., 2019; Itoh et al., 1998] However, the influence of the female cycle phases on single-legged balance and jumping tests in amateur female football players is not yet clear in literature and should be further investigated. Therefore, to ensure effective prevention strategies during the menstrual cycle phase in female football, the aim of this study was to determine differences in single-legged balance and jumping tests between the two phases of the menstrual cycle (follicular vs luteal) in female amateur football players. Due to the hormonal aspect, a worse functional performance during the first phase of the first cycle (follicular) is to be assumed for both balance and jumping tests. Methods: Cross-sectional study. 17 female amateur football players (26.82 ± 5.39 years) were tested twice during the follicular (T1) and luteal (T2) phase of the menstrual cycle by using the Y-Balance Test (Move2Perform®, Evansville, IN, USA) and the Single-leg Jump for Distance Test (SLJ). The tests were executed on a therapeutic mat (Fuchsius multimedia GmbH, RehaMatte, Munchen, Germany). As for the quantitative performance, the single-legged composite score (CS % = anterior + posterior lateral + posterior medial / 3 x leg length x 100) was calculated for the YBT, while the single-legged jumped distance relative to the participants height (% = jumped distance/height) was calculated for the SLJ. The limb symmetry index (LSI % = non-dom leg/dom leg x 100) was calculated for both tests. [Scinicarelli et al., 2021-A; Scinicarelli et al.,2021-B] The descriptive statistical analysis was carried out using the program "RStudio, Version 1.3.959, 2019-2020 RStudio, PBC". The data were organized as mean value ± standard deviation. The quantitative results of the functional performance tests were included in the analyses. Initially, the data was checked for normal distribution using the Shapiro-Wilk test. Subsequently, t-tests for dependent samples were carried out for normally distributed data and the Wilcoxon test for non-normally distributed data. The significance level was set at α ≤ 0.05. In addition, to illustrate the practical relevance, the effect sizes were calculated using Cohen's d [Cohen, 2013]. Results: The results of this study showed no significant differences in single-leg functional performance between T1 and T2 for both tests: YBT (T1 vs T2: dom, p = .660; non-dom, p = .193; LSI, p = .841) and SLJ (T1 vs T2: dom, p = .200; n-dom, p = .415; LSI, p = .567). Interlimb asymmetries (LSI < 90%) have been found within T1 and T2 for all participants (n = 17) during the YBT and for most of the participants (T1, n = 9; T2, n = 7) during the SLJ. For the YBT, single-leg balance deficits (CS < 94%) were observed in both T1 (n = 12, dom; n = 13, n-dom) and T2 (n = 14, dom; n = 8, n-dom) in more than half of the participants. For the SLJ, single-leg jumping deficits (jumped distance < 70% of participant height) were also observed both at T1 (n=10, dom; n=10, non-dom) and T2 (n=9, dom; n = 9; non-dom) in more than half of the participants. Conclusion: This study contributes to a better understanding of the relation between the female cycle phases and the balance and jumping performance, in order to further advance the planning and designing of prevention and rehabilitation strategies in female football players. The results of this study suggest that the different menstrual cycle phases (follicular and luteal) have no influence on functional performance in balance and jumping tests. Thus, a worse functional balance as well as jumping ability during the first phase of the cycle cannot be demonstrated by this study. However, interlimb asymmetries as well as single-leg balance and jumping deficits were found in the majority of participants in both menstrual cycle phases. This suggests a poor functional performance of the amateur female football players in question, regardless of whether they are in the luteal or follicular phase. Therefore, preventive and individual training programs focused on balance and jump/landing skills would be recommended during the entire menstrual cycle in order to counteract performance deficits and interlimb asymmetries . Finally, further studies should ensure a more valuable injury prevention approach by the inclusion of motion quality analysis during the menstrual cycle phase.