Strength training & menstrual cycle in badminton

The purpose of this section is to enhance comprehension of the menstrual cycle in female athletes, with a specific focus on female badminton players, and provide with some guidance that could be taken into consideration in female badminton players’ routines to optimize their strengthen conditioning.

There is a clear lack of evidence-based recommendations on individualizing strength training according to the menstrual cycle in female badminton athletes.

Nevertheless, it is well established that strength training is a crucial component of performance for badminton athletes, both male and female. It builds muscular strength and endurance, reducing the risk of injuries by stabilizing joints and supporting connective tissues during explosive movements, quick changes in direction, and repetitive motions. Strength training also enhances muscle power and explosiveness, enabling badminton athletes to generate more force in strokes and movements such as smashing, jumping, or lunging. Improved speed and agility are essential for reacting quickly to opponents' shots and maintaining optimal positioning during rallies. Additionally, strength training improves muscular endurance, delaying fatigue onset and enabling sustained performance throughout matches and training sessions. It also contributes to factors such as balance and stability, muscle imbalance correction, and psychological benefits.

For female badminton athletes, optimizing strength training can add value to training and competition, not only for high-performance and elite players but also for younger categories such as junior players. Understanding the physiological changes in their bodies and how they manifest can help players and coaches optimize their training sessions.

While recent research remains unclear regarding whether one menstrual cycle phase offers better strength improvement than another (follicular phase vs. luteal phase), clear physiological patterns play a key role and should be taken into consideration when planning a female badminton player program.

Physiologically, estrogen levels rise during the late follicular and ovulatory phases and remain elevated in the mid-luteal phase. Estrogens induce anabolic and muscle-building processes in females, enabling muscle fibers to generate greater force (Lowe et al., 2010). Additionally, free testosterone levels increase in the late follicular phase, which may be related to increased muscle diameter (Sung et al., 2014). Furthermore, during the late follicular and ovulatory phases, estrogens concentration is not affected by the rise in progesterone concentration, unlike the mid-luteal phase where both hormones remain high, potentially impacting estrogen's anabolic effect negatively due to the catabolic influence of progesterone (McNulty et al., 2020).

Considering these physiological responses, and taking into consideration how the catabolic effect of progesterone can notably influence the estrogens’ role, it could be beneficial to emphasize strength training during the late follicular and ovulatory phases of the menstrual cycle where the estrogens are acting at their highest peak without being influenced. On the contrary, it would make sense to reduce it at the beginning of the follicular phase, just when menses occur and where there is a significant drop in oestrogen and progesterone levels, which could unleash to flooding, reduced energy levels, worry, distraction, fluctuating emotions, and reduced motivation (Findlay et al., 2020). In addition, during the late luteal phase and despite the estrogen’s levels being still high, the effect of progesterone prevails, which might as well reduce the ultimate outcome. Nevertheless, it is important to always bear in mind that a female badminton athlete's performance is multifactorial, influenced not only by the menstrual cycle and its hormones, but also by factors such as sleep quality, personal life, nutrition, lifestyle, previous injuries, training loads, stress, among many other factors. Consequently, it is recommended to adopt a personalized approach based on each female badminton athlete's response to exercise performance across the menstrual cycle, as everyone can have a different response depending on the environment and circumstances that are being faced at a particular time.

Risk of ACL injury in female badminton players and menstrual cycle

The aim of this section is to explain the relationship between hormonal fluctuations in the MC and anterior cruciate ligament (ACL) injuries in badminton players. Additionally, it aims to identify the phase of the menstrual cycle during which women may be more susceptible to sustaining such injuries.

In general, women are estimated to be approximately five times more prone to ACL injuries than men when engaging in comparable levels of exercise. In badminton, one common scenario leading to such injuries is the execution of a single-leg landing task following a backcourt backhand side overhead stroke (Zang et al., 2023). According to Kaldau et al. (2024), data from the Danish National Patient Register, covering patients in Denmark from 2000 to 2018 with a diagnosis of ACL rupture who identified badminton as their primary sport, were analyzed for return to sport (RTS) and return to performance (RTP) after ACL injury. Out of these patients, 396 (63%) returned to playing badminton, but only 117 (19%) regained their pre-injury performance level. Additionally, both RTS and RTP rates were higher in male compared to female badminton players, highlighting the importance of continued investigation into this matter.

Several relevant factors contribute to the origin of ACL injuries, including musculoskeletal and neuromuscular differences. Zang et al. (2023) found that female athletes exhibit significantly lower absolute and normalized leg stiffness, as well as knee stiffness during landing, compared to male athletes. This suggests that female athletes may be more susceptible to non-contact ACL injuries during landing motion due to lower leg dynamic stability and higher knee hypermobility.

Another contributing factor is weak gluteal strength, which predisposes individuals to hip muscle fatigue and subsequent knee instability (Hu et al., 2023). Moreover, Anne Benjaminse et al. highlighted the significant effect of fatigue on ACL injury risk during exercise. This underscores the importance of addressing muscle fatigue, particularly in the gluteal muscles, to mitigate ACL injury risk in female badminton players. Injuries in badminton players, including ACL injuries, are influenced by a variety of factors such as biomechanical, anatomical, environmental, and hormonal aspects.

One hormonal factor that might as well impact the predisposition to ACL injury is the hormonal fluctuations during the menstrual cycle. Although the precise relationship between the menstrual cycle, fluctuation of female sex hormones, and subsequent injuries still remains to be clarified, there are correlations associated with physiological variations resulting from increased estradiol levels. These variations include joint and ligament laxity, reduced strength, and impaired neuromuscular control (Martinez-Fortuny et al., 2023; Khowailed et al., 2015), which are correlated with an increase of injury.

A systematic review of 408 athletes revealed an increased incidence of non-contact ACL injuries during the preovulatory (first half) phase of the menstrual cycle, occurring between the menses (1-5 days) and the ovulation (6-15 days).

The ovulation phase corresponds to the period of highest estradiol levels. However, this factor does not necessarily coincide with the peak risk of injury (Hewett et al., 2007).

In badminton, where injury risk is multifactorial and individual, it is imperative for players and coaches to recognize the physiological variations associated with the menstrual cycle that may affect their neuromuscular control and being able to identify them (in some of the cases), as well as communicate them. Awareness of these factors enables coaches to tailor physical preparation programs, on and off court, to mitigate the incidence of ACL injuries.

By acknowledging the unpredictable nature of badminton and being aware of the phases where the release of certain hormones such as relaxin and estradiol occurs, the coaches and athletes may find it beneficial, (as long as the athlete’s time and schedule allow it) an approach that involves reducing the unpredictability of on-court exercises, to minimize the risk of injury caused by increased joint and ligament laxity combined with impaired neuromuscular control together with a major focus on strength conditioning during the preovulatory phase, and most particularly during the late follicular phase when estrogen levels peak, could be beneficial too.

Emphasizing strength training during this time could be an optimal period to incorporate specialized exercises to reduce the ACL injury risk. Current research suggests that programs including isokinetic strength exercises for knee flexor and extensor muscles might help badminton players with movement control. Furthermore, strengthening the hip and gluteal muscles is crucial, as this can improve knee stability (Hu et al., 2023) and maintain dynamic valgus control (Pournasiri et al., 2023).

By implementing certain adaptations in the athlete’s sessions, coaches could potentially mitigate ACL injury risks and optimize performance, recognizing the physiological nuances that might impact female athlete’s well-being and performance.