Association between perimenstrual symptoms and static balance in young women: a preliminary longitudinal observational study

Abstract

Background

Perimenstrual symptoms are physiological and psychological responses to fluctuations in female hormone levels. These symptoms, which include physical discomfort such as lower abdominal pain and emotional changes such as irritability and depression, affect over 80% of women of reproductive age and vary in type and severity depending on the menstrual phase. Static balance, which plays a fundamental role in motor coordination and is influenced by various systems, may be affected by these symptoms. Although changes in balance across menstrual phases have been examined, the relationship between perimenstrual-symptom severity and static balance has not been fully investigated. This study aimed to explore the relationship between static balance and the severity of perimenstrual symptoms during the menstrual, postmenstrual, ovulatory, and premenstrual phases in young women.

Methods

Eighteen women with eumenorrhea were enrolled. Static balance was measured by recording the women’s postures for 30 s while standing on one leg at four time points: during menstruation, postmenstruation, ovulation, and premenstruation. Symptoms during the perimenstrual period were measured with the Menstrual Distress Questionnaire (MDQ), which includes subsections on pain, concentration, behavioral change, autonomic reaction, water retention, and negative affect.

Results

During the menstrual phase, significant correlations were identified between total trajectory length and both pain (r = 0.527, P = 0.025) and concentration (r = 0.500, P = 0.035). In the premenstrual phase, the total MDQ scores were correlated with the total trajectory length (r = 0.570, P = 0.013). No significant correlations were found between the total MDQ scores and trajectory length during the postmenstrual or ovulation phases.

Conclusions

This study first demonstrated a relationship between perimenstrual-symptom severity and static balance. Total trajectory observed a significant correlation with body pain and concentration during the menstrual phase and with MDQ scores during the premenstrual phase. These results suggest that young women with more severe symptoms during their menstrual cycle may have reduced balance ability. Evaluating symptom severity, in addition to menstrual phase, may be useful when assessing performance-related functions such as static balance, but further studies are warranted.

Background

Perimenstrual symptoms are a unique phenomenon related to female hormone fluctuations, with most women experiencing various physical, mental, and social symptoms during their menstrual cycle [1]. Specifically, lower abdominal pain can occur during menstruation, and negative emotions such as depression and irritability often develop before menstruation [2]. According to a previous survey, over 80% of young women experience certain perimenstrual symptoms, [3] which vary in type and severity, depending on the stage of the menstrual cycle. These may represent health problems that affect women throughout the menstrual cycle. In particular, symptoms associated with the menstrual cycle can hinder the maintenance of exercise performance in female athletes [4]. Thus, in a large-scale survey, the prevalence and frequency of menstrual cycle symptoms were shown to be associated with the availability to train and compete in exercising women [4]. Approximately 90% of these female athletes were aware of changes in their menstrual cycles and subjective conditions [4].

Static balance, also referred to as postural control, is a fundamental component of motor coordination,⁵ defined as the ability to maintain the body’s center of gravity within the base of support. It depends on the integration of sensory information from the visual, vestibular, and proprioceptive systems, along with coordinated muscular responses. Alterations in any of these systems, including sensory, musculoskeletal, or cognitive factors, can affect balance [5, 6] Impaired static balance can increase the risk of injury (e.g., anterior cruciate ligament tears and ankle sprains) and reduce performance in stability-dependent movements (e.g., jump landings and directional changes) [7]. It has been reported that 48% of young adults experienced at least one fall over a 16-week period, with 10% suffering injuries from these falls [8]. Notably, women were the only group to experience severe injuries such as fractures or concussions. These findings highlight that falls can occur even in young women during daily, non-sports activities, emphasizing the importance of assessing postural balance in this population.

Fluctuations in hormones, including estrogen and progesterone, are thought to influence gamma-aminobutyric acid (GABA) and monoaminergic pathways and contribute to alterations in postural control across the menstrual cycle [9]. Static balance has been reported to decline during the late luteal (premenstrual) phase in conjunction with changes in blood hormone levels [10]. Several studies have also examined the relationship between menstrual cycle phases and static balance, and a recent systematic review has reported that hormone fluctuations across the menstrual cycle can affect postural control, although findings are not always consistent [9]. Moreover, despite the high prevalence of perimenstrual symptoms and their variation across menstrual phases and individuals, [4] no previous studies have specifically investigated the relationship between perimenstrual symptoms and static balance [9].

This study aimed to investigate the relationship between perimenstrual symptom severity and static balance in each menstrual cycle phase (i.e., during menstruation, postmenstruation, ovulation, and premenstruation). Participants with more severe perimenstrual symptoms were hypothesized to exhibit poorer static balance.

Methods

Study design and participants

This study was conducted as a longitudinal observational study. A longitudinal design was adopted because it allowed each participant to serve as her own control, enabling us to detect intra-individual variations in static balance across different phases of the menstrual cycle.

For participant recruitment, a poster was posted within the university. During the period leading up to the start of the study, interested individuals were provided with an explanation of the study procedures, instructed on how to measure their basal body temperature (BBT), and evaluated to confirm whether they met the inclusion criteria. Participants were recruited exclusively among university affiliates, constituting a convenience sample, and a total of 33 female participants were recruited. This recruitment strategy was adopted primarily for ethical reasons. In this study, the eligibility criteria were as follows: ⅰ) normal menstrual cycle of 25–38 days, ⅱ) age 18–25 years, [11, 12] ⅲ) non-use of low-dose oral contraceptives or other hormone therapy in the previous 6 months, ⅳ) absence of gynecological diseases currently or previously under treatment, v) the biphasic basal body temperature could be confirmed, vi) no regular exercise habits, and vii) no history of orthopedic disorders in the lower limbs within the past 6 months. In general, after ovulation, progesterone secretion increases, leading to a rise in basal body temperature. Therefore, the menstrual cycle can be divided into a low-temperature phase and a high-temperature phase. Failure to observe a biphasic basal body temperature indicates that ovulation did not occur. Participants with irregular menstrual cycles did not meet the inclusion criteria and were excluded before the start of the measurements. In addition, those whose menstrual cycles became irregular during the measurement period were also excluded from the analysis.

The post-hoc power analysis was conducted with G*Power 3.1 software (Kiel University, Germany) using a r of 0.570 for the correlation coefficient between the total Menstrual Distress Questionnaire (MDQ) score and the total trajectory length. The post-hoc power analysis based on a t-test and correlations with a moderate effect size (d = 0.57) and an alpha level of P < 0.05 showed a statistical power of 0.789. All participants received a full explanation of the study procedures and measurements, and written informed consent was obtained. The study was conducted in a single-blinded manner. Although participants were aware of their own menstrual cycles, they received no information about the study’s specific hypotheses or expected outcomes in order to minimize potential bias. Recruitment and scheduling staff had access to information about participants’ menstrual cycles; however, they were not involved in the measurement sessions nor in the data analyses. This study was conducted in compliance with the guidelines of the Declaration of Helsinki and its amendments and was approved by the Ethical Committee for Epidemiology of Hiroshima University (E2022-0192). The study was designed and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines to enhance transparency and reproducibility [13].

Timing of measurements

The participants were given a basal thermometer (Citizen Electronic Thermometer CTEB503L; Citizen Systems Co., Ltd., Tokyo, Japan) and asked to record their basal body temperature. The use of a basal thermometer, which can detect subtle temperature changes with high precision, is widely recognized in clinical and research settings as a standard and reliable method for BBT measurement. They were also administered an ovulation test kit (Doctor’s Choice One Step Ovulation Test Clear; Beauty and Health Research Inc., Torrance, CA, USA) to determine the day of ovulation. Ovulation test kits, which detect the concentration of luteinizing hormones (LH), have been reported to have high concordance with blood LH surge, with many commercially available kits showing over 90% agreement, [14] supporting the reliability of ovulation detection in this study. Perimenstrual symptoms and static balance were measured in the four phases of a single menstrual cycle, i.e., during menstruation, postmenstruation, ovulation, and premenstruation. Measurements for each phase were conducted over approximately one hour. Participants were not subjected to any specific restrictions regarding prior activities. During menstruation, the test was conducted 1–3 days after the start of menstruation; during postmenstruation, 3–4 days after the end of menstruation; during ovulation, 2–4 days after the day when the ovulation test kit showed a positive result; and during premenstruation, within 7 days of the expected start of menstruation. Although the measurement timing was not randomized, the measurements were conducted according to the predefined phases of the menstrual cycle described above. The menstrual cycle in which the measurements started was not unified across participants and varied individually. Because cycle length varied among participants, the timing of measurements was determined relative to each participant’s own cycle using BBT and ovulation test results.

Basic participant information

The following basic information was collected: age, age at menarche, height, and weight. Body mass index (BMI) was calculated using weight and height (kg/m²). The mean and standard deviation values of the patients’ age, age at menarche, height, weight, and BMI were 21.6 ± 1.4 years, 12.8 ± 1.2 years, 158.9 ± 6.1 cm, 52.0 ± 5.3 kg, and 20.6 ± 1.7 kg/m², respectively.

Measurements of perimenstrual symptoms

The severity of perimenstrual symptoms was assessed using the MDQ developed by Moos [15]. The MDQ is used to evaluate perimenstrual symptoms from physical, mental, and social perspectives according to the menstrual cycle phase, and its Japanese version has been validated [16]. Moos classified 46 complaints into eight subscales: “pain,” “concentration,” “behavioral change,” “autonomic reaction,” “water retention,” “negative affect,” “arousal,” and “control.” Thirty-five items were evaluated from six subscales after excluding “arousal” and “control,” which are less common among Japanese people [16]. Participants were asked to answer the MDQ at every measurement. Responses were scored using a 6-point Likert scale, with scores ranging from 1 (no reaction at all) to 6 (acute or partially disabling) and higher scores indicating greater severity of perimenstrual symptoms.

Measurements of static balance

To measure static balance, a force plate (T.K.K.5810; Takei Scientific Instruments Co., Ltd., Japan) with a sampling frequency of 100 Hz was used. Participants were instructed to stand on one leg with bare feet and maintain a stationary posture for 30 s after stabilization, during which oscillations of the center of pressure (CoP), which reflects postural sway as the orthogonal projection of the body’s center of gravity, were recorded (Fig. 1). To prevent auditory stimuli from affecting the measurement results, all measurements were conducted in a quiet room without noise. The measurement position was with the right leg (dominant leg) as the supporting leg, the left leg lifted with the hip and knee joints in a slightly flexed position, and the hands held in front of the chest [17]. The position of the supporting foot was standardized so that the intersection of the second metatarsal bone and the navicular bone was aligned with the center of the force plate. Before the actual measurements, participants practiced the task three times to become sufficiently familiar with the single-leg stance. In addition, considering that fatigue may affect the results, a two-minute rest period was provided between trials, and participants’ subjective fatigue was checked throughout the measurements. Five parameters were measured on the force plate: total trajectory length (mm), center of pressure mean velocity (CoPv) (mm/s), center of pressure surface area (CoPs) (mm²), X-axis trajectory length (mm), and Y-axis trajectory length (mm) [18, 19]. Total trajectory length (mm) is the combined distance between the X- and Y-axis movements. X-axis trajectory length (mm) indicates the distance moved horizontally, and Y-axis trajectory length (mm) denotes the vertical distance covered by a point or object. The CoPv (mm/s) is used to measure the speed of movement. The CoPs (mm²) are the region enclosed by the outermost points. Participants performed three trials for each menstrual phase, and the mean values of the three successful trials were analyzed.

Fig. 1.

Posture used for static balance measurement and plot diagram of the calculation parameters

Statistical analysis

All data were analyzed using IBM SPSS Statistics for Windows (version 29.0; IBM Corp., Armonk, NY, USA). The Shapiro–Wilk test was performed to check the normality of each measured value. Pearson’s or Spearman’s rank correlation coefficient was evaluated to examine the relationship between MDQ scores and static balance outcomes for each menstrual cycle phase. As a sub-analysis, repeated-measures analysis of variance or Friedman’s test was conducted to check for changes in perimenstrual symptoms and static balance outcomes for each menstrual cycle phase, depending on the normality of the data. Since this was a preliminary study, no adjustments were made for multiple comparisons [20]. The level of significance was set at P < 0.05.

Results

Participants who met the exclusion criteria, those who declined participation, and those with measurement data gaps were excluded, resulting in a final participant number of 18 women (Fig. 2).

Fig. 2.

Flowchart of participant recruitment for this study

Table 1. shows the correlation between MDQ scores, which indicate perimenstrual symptoms, and static balance parameters. Figure 3 illustrates a scatter diagram of MDQ scores and total trajectory length, a static balance parameter. These charts show correlations for pain, concentration, and total trajectory length during menstruation (pain: r = 0.527, P = 0.025; concentration: r = 0.500, P = 0.035). In the premenstrual phase, a correlation was observed between the total MDQ score and total trajectory length (r = 0.570, P = 0.013). No correlation was observed between total MDQ scores and total trajectory length in the postmenstrual or ovulation period.

Table 1.

Correlation between MDQ and static balance outcomes

Menstrual phases	Variables		MDQ
			Pain		Concentration		Behavioral change		Autonomic reaction		Water retention		Negative affect		Total
			r	P	r	P	r	P	r	P	r	P	r	P	r	P
During menstruation	Total trajectory length	(mm)	0.527*	0.025	0.500*	0.035	0.460ª	0.055	0.233	0.352	-0.068	0.788	0.439	0.069	0.447	0.063
	CoPv	(mm/s)	0.541*	0.021	0.492*	0.038	0.460ª	0.055	0.245	0.326	-0.060	0.812	0.441	0.067	0.450	0.061
	CoPs	(mm²)	0.317	0.200	0.116	0.646	0.268	0.282	-0.028	0.911	-0.310	0.211	0.314	0.205	0.186	0.460
	X-axis trajectory length	(mm)	0.304	0.221	0.328	0.184	-0.051	0.841	0.198	0.432	-0.005	0.984	0.201	0.423	0.100	0.692
	Y-axis trajectory length	(mm)	-0.126	0.619	0.241	0.335	-0.293ª	0.238	-0.126	0.619	-0.218	0.384	-0.076	0.764	-0.296	0.232
Postmenstruation	Total trajectory length	(mm)	0.062	0.808	0.170	0.500	0.200ª	0.936	0.232	0.355	-0.056	0.824	0.202	0.422	0.067	0.791
	CoPv	(mm/s)	0.062	0.808	0.170	0.500	0.210ª	0.935	0.232	0.355	-0.056	0.824	0.202	0.422	0.067	0.791
	CoPs	(mm²)	0.039	0.879	0.061	0.811	0.285ª	0.252	0.056	0.826	-0.049	0.848	0.119	0.637	0.058	0.820
	X-axis trajectory length	(mm)	-0.249	0.318	-0.303	0.221	-0.532ª*	0.023	0.017	0.946	0.112	0.659	-0.202	0.422	-0.220	0.042
	Y-axis trajectory length	(mm)	-0.082	0.745	0.067	0.791	-0.185ª	0.463	0.462	0.054	0.063	0.804	-0.172	0.494	0.380	0.867
Ovulation	Total trajectory length	(mm)	0.013	0.960	-0.014	0.955	-0.146ª	0.564	-0.038	0.881	-0.104	0.681	0.034	0.893	0.023	0.928
	CoPv	(mm/s)	0.013	0.960	-0.014	0.955	-0.146ª	0.562	-0.038	0.881	-0.104	0.681	0.034	0.893	0.023	0.298
	CoPs	(mm²)	0.030	0.906	0.063	0.804	0.116	0.646	-0.025	0.922	0.000	1.000	0.084	0.740	0.120	0.635
	X-axis trajectory length	(mm)	0.061	0.911	0.530*	0.024	0.242ª	0.333	0.260	0.298	0.027	0.917	0.333	0.177	0.172	0.495
	Y-axis trajectory length	(mm)	-0.117	0.482	-0.057	0.821	-0.372ª	0.129	0.172	0.495	-0.085	0.737	-0.098	0.698	-0.149	0.555
Premenstruation	Total trajectory length	(mm)	0.457	0.057	0.385	0.115	0.408ª	0.093	0.241	0.336	0.160	0.525	0.450	0.061	0.570*	0.013
	CoPv	(mm/s)	0.457	0.057	0.385	0.115	0.408ª	0.093	0.241	0.336	0.160	0.525	0.450	0.061	0.570*	0.013
	CoPs	(mm²)	0.099	0.696	0.050	0.843	0.144	0.569	0.101	0.691	-0.426	0.078	0.090	0.723	0.083	0.744
	X-axis trajectory length	(mm)	-0.018	0.943	0.374	0.236	-0.022ª	0.932	0.164	0.516	0.501*	0.034	0.164	0.515	0.186	0.460
	Y-axis trajectory length	(mm)	-0.219	0.384	-0.363	0.139	-0.447ª	0.063	-0.122	0.630	-0.196	0.436	-0.210	0.403	-0.280	0.261

MDQ Menstrual Distress Questionnaire, CoPs Center of pressure surface areas, CoPv Center of pressure mean velocity

ª was tested with Pearson’s correlation coefficient, and the other items were tested with Spearman’s rank correlation coefficient

*P < 0.05

Fig. 3.

Plot diagram of the correlation between the Menstrual Distress Questionnaire total score and the total trajectory length

Table 2 lists all MDQ scores and static balance outcomes for each menstrual cycle phase. MDQ pain, behavioral change, water retention, and total scores showed statistically significant fluctuations with the menstrual cycle (pain, P = 0.010; behavioral change, P = 0.001; water retention, P = 0.044; and total, P = 0.002). No significant changes were observed in static balance outcomes when comparing each menstrual phase for any of the parameters, including total trajectory length (P > 0.05).

Table 2.

MDQ scores and static balance outcomes for each menstrual cycle

			During menstruation	Postmenstruation	Ovulation	Premenstruation	P	Effect size (r)
MDQ	Pain		11.5 [9.0, 15.8]	10.5 [6.3, 13.8]	7.0 [6.0, 9.0]	11.0 [8.0, 15.5]	0.010*	0.151
	Concentration		10,0 [9.3, 11.6]	9.5 [8.0, 12.0]	9.0 [8.0, 9.0]	10.5 [9.0, 14.5]	0.119	0.128
	Behavioral change		11.6 ± 3.4	9.1 ± 2.7	6.5 [5.0, 8.0]	11.6 ± 5.3	0.001*	0.166
	Autonomic reaction		4,0 [4.0, 5.75]	4.0 [4.0, 5.0]	4.0 [4.0, 4.8]	4.0 [4.0, 5.8]	0.516	0.102
	Water retention		7.0 [5.3, 9.0]	4.5 [4.0, 8.0]	6.5 [5.0, 8.0]	6.5 [5.0, 8.0]	0.044*	0.139
	Negative affect		11.5 [9.0, 13,8]	9.0 [8.0, 12.8]	8.5 [8.0, 10.8]	12.0 [8.3, 17.8]	0.075	0.134
	Total		57.0 [49.0, 65.5]	50.0 [39.5, 61.0]	40.0 [37.3, 48.8]	58.0 [43.3, 77.5]	0.002*	0.163
Static balance	Total trajectory length	(mm)	839.2 ± 210.3	768.9 ± 207.1	806.6 ± 220.7	798.2 ± 196.8	0.299	0.262
	CoPv	(mm/s)	28.1 ± 7.0	25.7 ± 6.9	27.0 ± 7.4	26.7 ± 6.6	0.298	0.262
	CoPs	(mm²)	584.6 [458.3, 670.8]	507.7 ± 159.8	578.8 [450.4, 646.9]	565.2 [478.9, 607.3]	0.133	0.279
	X-axis trajectory length	(mm)	9.6 [7.7, 12.5]	7.3 ± 6.1	10.0 ± 5.9	9.0 [5.4, 12.6]	0.435	0.195
	Y-axis trajectory length	(mm)	−7.5 ± 29.6	0.7 ± 25.7	−5.1 ± 26.1	6.6 ± 27.3	0.050	0.376

Repeated-measures analysis of variance was conducted for total trajectory length, CoPv, and Y-axis trajectory length. Friedman’s test was used for all MDQ scores, CoPs, and X-axis trajectory length 

Data are expressed as mean ± standard deviation or median [1st quartile, 3rd quartile]

MDQ Menstrual Distress Questionnaire, CoPs Center of pressure surface areas, CoPv Center of pressure mean velocity

*P < 0.05

Discussion

This study investigated the relationship between perimenstrual symptoms and static balance during the four phases of the menstrual cycle. The results revealed a correlation between perimenstrual symptom severity and static balance, with a relationship also confirmed between MDQ subscales, such as pain and concentration during menstruation, and static balance. These findings offer novel insights into perimenstrual symptom severity in relation to static balance. In contrast, no significant variation in static balance was observed across menstrual cycle phases in this study, adding data to prior studies with mixed findings on the influence of menstrual cycle phase on balance.

The relationship between menstrual pain and static balance was examined. During menstruation, MDQ pain symptoms are strong, which are related to the excessive production and release of prostaglandin, a pain-causing substance, in the endometrium [21, 22]. Pain associated with menstruation is considered to be chronic because it recurs approximately once a month, [23] and one of the characteristics of chronic pain is that it increases by catastrophizing [24]. Previous research has shown that people with a greater tendency to experience pain catastrophizing tend to overestimate the severity of painful stimuli, which leads to increased muscle tension in the trunk and avoidance of excessive spinal movement [25]. Moreover, people with chronic lower back pain have a poorer ability to control their posture and a slower rate of trunk muscle contraction than those without [26]. Furthermore, people with a strong tendency to experience pain catastrophizing and high pain severity have poorer static balance [27]. Thus, those with more severe menstrual pain may experience an increase in catastrophizing and a decline in trunk postural control, leading to poorer static balance. However, the interpretation that catastrophizing leads to impaired trunk postural control and reduced static balance ability is highly tentative and should be considered with caution.

The relationship between the premenstrual total MDQ score and static balance was also considered. During the premenstrual period, progesterone, which increases after ovulation, rapidly decreases, and this hormonal change may influence GABA receptor function in the central nervous system [28, 29]. GABA receptors are also involved in motor control by the cerebellum and vestibular system, contributing to static balance [30]. While our data showed an association between the premenstrual total MDQ score and balance, it cannot be directly attributed to emotional symptoms such as anxiety or depression or to central nervous system sensitivity. It is noteworthy, however, that negative affect in participants tended to be higher during the premenstrual phase compared with other phases, even though the differences were not statistically significant. Therefore, although the findings suggest a potential link between overall symptom burden and static balance, interpretations regarding underlying physiological or emotional mechanisms should be made cautiously.

One possible explanation for the absence of significant differences in static balance across menstrual phases is that the central nervous system may rapidly adapt to systemic changes, including hormonal fluctuations. Although fluctuations in estradiol may influence the mechanical properties of connective tissues, human studies suggest that such peripheral changes do not necessarily translate into behavioral alterations such as voluntary movement or postural control [31, 32]. Therefore, the present findings support the notion that postural control remains robust against short-term hormonal fluctuations, possibly due to rapid compensatory mechanisms within the central nervous system [33]. At the same time, the observation that significant correlations were found between individual symptom severity (e.g., pain and concentration) and balance measures, despite the absence of group-level menstrual phase differences, should not be considered contradictory. Thus, these results suggest that some participants may experience transient symptom-related changes in balance during menstruation or the premenstrual phase. However, group-level comparisons require consistent and robust effects across all participants. Given the substantial variability in symptom manifestation and severity among individuals, within-phase fluctuations may occur without producing statistically significant between-phase differences. Taken together, our findings support the view that static balance is robust against short-term hormonal fluctuations at the group level, while individual differences in symptom severity can still influence balance performance.

This study investigated the impact of perimenstrual symptoms on female performance by focusing on static balance. In addition, no changes in static balance were observed throughout each menstrual cycle in the sub-analysis, consistent with previous findings [34]. The relationship between the menstrual cycle and performance fluctuations has also been discussed in other studies [35, 36]. Previous large-scale research has demonstrated that the prevalence and frequency of menstrual cycle symptoms are associated with reduced availability to train and compete in exercising women [4]. Moreover, recent evidence suggests that perceived negative menstrual cycle symptoms, rather than fluctuations in estrogen or progesterone, are directly related to impaired race performance in female athletes [35]. Therefore, this study highlights the need to evaluate not only fluctuations in the performance of the overall menstrual cycle but also individual factors including symptoms. The severity and type of perimenstrual symptoms vary greatly from person to person; however, few previous studies on the relationship between the menstrual cycle and static balance have investigated specific symptoms for each menstrual cycle phase. The results of this study suggest that attention should be paid to individuals experiencing severe pain and concentration difficulties during the menstrual phase, and to those with a generally high overall symptom burden during the premenstrual phase. The subjective condition of female athletes associated with their menstrual cycle has been noted to worsen during and before menstruation, [4] corresponding to the period when a correlation is observed between perimenstrual symptoms and static balance. The absence of a relationship between perimenstrual symptom severity and static balance in the postmenstrual and ovulation periods may have been because, unlike during and before menstruation, there was no range of symptom severity among the participants. In addition, the correlation coefficients between perimenstrual symptoms and total trajectory length (r ≈ 0.50–0.57) indicate moderate relationships. These correlations correspond to approximately 25–32% of the shared variance (r² ≈ 0.25–0.32), suggesting that while a portion of the variability in balance outcomes is associated with perimenstrual symptoms, other factors also contribute. The clinical significance of these moderate correlations remains to be determined, highlighting the need for further research to assess their implications regarding the risks for falls and injuries.

This study has several limitations. The first limitation concerns the study design and sample size. Thus, the sample size was small, making the statistical power inadequate, and multiple comparison corrections not possible to perform considering the risk of statistical false errors. Given that multiple correlation analyses were conducted without corrections for multiple comparisons, the present study should be considered exploratory in nature. The results should be interpreted with caution, and replication in larger, adequately powered samples is required to confirm the observed associations. Moreover, athletes were not included among the participants, making direct extrapolation to athletic populations difficult. In addition, in this longitudinal study, factors other than perimenstrual symptoms, such as sleep, stress, fatigue, and exercise habits that cause fluctuations, may not have been standardized for each participant. The second limitation concerns the constraints of measurement and assessment. In this study, only static balance was evaluated, and tasks closer to actual sports movements, such as dynamic balance, were not conducted. Moreover, static postural balance was assessed using a single test condition. A more comprehensive evaluation would require assessments under several sensory manipulation conditions (e.g., eyes open, eyes closed, and on firm or foam surfaces) and in different postures (e.g., bipedal, unipedal, semi-tandem, and tandem). In addition, the extent to which changes in CoP reflect clinically meaningful balance alterations remains unclear [37]. Future studies could combine CoP measures with participants’ subjective perceptions of performance fluctuations and physical conditions to better clarify the functional significance of the observed changes in balance. Although participants were asked about a history of orthopedic disorders in the lower limbs within the past 6 months, ankle instability and a history of ankle sprains were not assessed. In addition, perimenstrual symptoms were assessed solely using the MDQ, which may not adequately capture ovulatory-phase symptoms, such as the mittelschmerz. This should be taken into account when interpreting the results from this menstrual phase. The final limitation concerns constraints in data interpretation. Although the MDQ is a widely used and validated tool for evaluating perimenstrual symptoms, interpretations regarding physiological mechanisms, such as emotional dysregulation or central nervous system sensitivity, based solely on MDQ scores are beyond the scope of this study. Finally, gynecological disorders were self-reported and not confirmed by medical examination, and the presence or absence of menstrual pain or premenstrual symptoms prior to participation was not formally assessed. These factors may have influenced both symptom severity and balance outcomes. In the future, this study will be expanded to include more factors and participants and clarify the impact of perimenstrual symptoms on performance.

Conclusions

This study showed that greater perimenstrual symptom severity during and before menstruation was associated with variations in static balance. These preliminary results suggested a potential link between perimenstrual symptoms and factors relevant to women’s exercise performance, although further investigation is warranted. Future research is warranted to explore these associations using more diverse and challenging balance tasks and to examine female athletes doing sports with various specific characteristics in order to better understand the potential impact on exercise performance in women.

Abbreviations

BBT

Basal body temperature

BMI

Body mass index

CoP

Center of pressure

CoPv

Center of pressure mean velocity

CoPs

Center of pressure surface area

GABA

Gamma-aminobutyric acid

ICC

Intraclass correlation coefficient

LH

Luteinizing hormones

MDQ

Menstrual Distress Questionnaire

Authors’ contributions

R.M. contributed to conceptualization, methodology, and writing – original draft. T.T. and S.A. developed the data collection procedures and analysis methods (methodology). S.O., A.I., R.Y., and M.K. were responsible for data curation and formal analysis. N.M. contributed to project administration and supervision. All authors reviewed and approved the final manuscript.

Funding

Not applicable.

Data availability

The data supporting the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was conducted in compliance with the guidelines of the Declaration of Helsinki and its amendments and was approved by the Ethical Committee for Epidemiology of Hiroshima University (E2022-0192). Informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.