Comparative Study of Plantar Load and Foot Posture Characteristics in Male Elite Squash Players and Non-Athletes in Taiwan

Introduction

Squash is a highly competitive and technically demanding sport that necessitates athletes to possess rapid and agile footwork, particularly in terms of quick acceleration and deceleration, repeated sprinting capability, and the ability to change directions swiftly [1]. Due to the necessity for squash players to frequently execute lunging and side-stepping movements, they often undergo rapid alterations in both the direction and speed of their movements [1]. This dynamic activity can impose significant stress on the lower limbs, potentially resulting in acute soft tissue injuries or overuse injuries affecting the knees and ankles [2–4]. A study examining injuries across various sports, including squash, gymnastics, and fencing, found that squash had the highest incidence of injuries, averaging 8.5 injuries per athlete [5]. A significant proportion of the injuries (67%) involved the lower extremities, with the foot and ankle identified as the most frequently affected regions (22%) [5]. Furthermore, these injuries were predominantly observed in male athletes, accounting for 80% of the cases [5,6]. Knee injuries were predominantly linked to overuse, while foot and ankle injuries were generally attributed to acute mechanisms [5].

Previous research has suggested that prolonged participation in racquet sports, such as badminton, can induce adaptive changes in the structural and functional characteristics of the feet [7]. Research by Mei et al reported that elite badminton players experience elevated peak pressure and force-time integrals on the forefoot and hallux during right-forward lunging steps [8]. Similarly, Valldecabres et al observed that, during lunge tasks performed under fatigue, elite badminton players exhibit a medial shift in plantar pressure on the midfoot of the non-dominant limb, indicating reduced stability and an increased risk of injury [9]. Yu et al further highlighted that badminton players demonstrate significantly higher peak forefoot pressure during the toe-off phase of left-forward and right-forward lunging steps, as well as during backward revolutions leading into jumps [10]. Conversely, during the touchdown phase of footwork, plantar pressure is concentrated on the rearfoot and lateral foot for forward lunges, while backward revolution to jump exhibited pressure concentrated on both the forefoot and rearfoot [10]. In tennis, advanced tennis players exhibit an increase in maximal force distribution on the forefoot of their dominant foot while executing a forehand stroke, whereas the opposite trend was noted, with an increase in force distribution on the rearfoot during backhand strokes [11]. Additionally, elite tennis players have been observed to allocate greater plantar loads to the lateral longitudinal arches and heels than to the medial regions during routine gait activities, a pattern that can reflect biomechanical adaptations to tennis-specific skills [12]. Based on these findings, the analysis of plantar pressure distribution emerges as a critical tool for understanding the development of foot patterns in specialized athletes [12–17]. It also facilitates the assessment of athletic performance and movement dynamics, as well as the evaluation of risk factors associated with lower extremity injuries.

With regard to postural control and center of gravity analysis, Du et al investigated the effects of fatigue on the postural stability of badminton players during lunging movements. Their findings revealed that fatigue significantly impaired postural control, as evidenced by notable increases in the area, displacement and distance of the center of pressure across various plantar sub-regions, particularly in the medial-lateral direction [18]. Similarly, studies on tennis players have demonstrated lower center of pressure sway in national-level athletes than in non-athletes, indicating superior postural balance among trained players [19]. Although existing studies highlight the critical role of the center of pressure in enhancing balance correction proficiency during sport performance, particularly in prevalent disciplines such as badminton and tennis, there remains a notable lack of research focusing on the center of pressure dynamics in squash discipline.

Assessment of static foot posture has been extensively used in clinical practice, primarily due to the recognition that pronated and supinated foot alignments are potential risk factors for lower limb injuries or can contribute to their occurrence [20]. For example, a prospective cohort study conducted by Safar Cherati et al demonstrated that abnormal foot postures in professional soccer players could elevate the risk of hamstring and medial collateral ligament injuries, as well as increase the duration of time lost due to lower extremity injuries [20]. In the context of badminton, elevated pressure beneath the medial region of the leading foot during lunging movements has been observed, potentially indicating a greater degree of pronation or arch collapse following fatigue. Such changes can result in a flatter foot posture, thereby increasing the risk of injury [9]. This observation is consistent with findings from previous studies, which reported significantly higher foot posture index scores among elite collegiate athletes participating in high-impact sports, such as badminton, basketball, and volleyball, than among sedentary controls. These findings suggest a potential relationship between engagement in high-impact sports and the development of a more pronated foot posture [21]. Based on a comprehensive analysis of these correlations in the above literature, it is evident that factors such as plantar load distribution (PLD), foot arch index (FAI), center of gravity, and rearfoot posture significantly influence athletic performance, postural balance, movement stability, and injury risk, particularly among racquet sports athletes [7–14]. These factors are closely linked to adaptive modifications in foot structure and function, which arise from prolonged training, competitive activities, fatigue, or overuse. Consequently, in this study, we hypothesized that these biomechanical and structural factors are intricately associated with footwork efficiency and interception skills exhibited by elite collegiate squash players, especially following extended training sessions.

To the best of our knowledge, no published studies have examined the effects of prolonged training and competitive experience on PLD, center of gravity performance, and foot postural characteristics in squash players. Consequently, there is a lack of quantitative data regarding the foot characteristics specific to this athletic population. Therefore, we aimed to compare PLD, FAI, and center of gravity measured using the JC Mat optical plantar pressure analyzer, and rearfoot posture evaluated using static calcaneal angle measurements in 26 Taiwanese elite squash players and 33 age-matched college students who did not play racquet sports. We hypothesized that the PLD and foot postural characteristics of the squash players in this study would exhibit similarities to those observed in tennis, badminton, and other racquet sport athletes, as suggested in previous research [12–14]. Specifically, we anticipated that the forefoot, rearfoot, and lateral foot regions would demonstrate higher load distribution. If the findings support this hypothesis, they could provide a foundation for future research to explore potential associations between the foot adaptations developed through long-term participation in racquet sports and the occurrence of musculoskeletal injuries in specific regions of the lower limbs.

Material and Methods

ETHICS STATEMENT:

This study was conducted in accordance with the principles outlined in the Declaration of Helsinki and its latest amendments and was approved by the Research Ethics Committee of the National Taiwan University, Taipei City, Taiwan, which granted approval for the investigators’ ethics application on June 13, 2015 (NTU-REC No.: 201506 ES016). All patients provided written informed consent before participating in the study.

PARTICIPANTS:

This cross-sectional survey study included 59 healthy male collegiate students recruited from various universities and colleges in Taiwan between June 2016 and July 2021. The study period also included subsequent data analysis and supplementation. Among the participants, 26 were elite squash players (referred to as the squash group), and 33 were college students of comparable age with no prior experience in squash or expertise in other sports disciplines (referred to as the control group). Due to the specific venue requirements for squash, the sport is not widely popular in Taiwan, which limited the number of elite squash players available for recruitment. The eligible squash players were selected from 32 male collegiate students who had participated in the open or general men’s singles and team competitions of the squash championships during the 105th to 110th academic years in Taiwanese universities. All selected players were right-handed, with their dominant limb corresponding to their stroke arm. The survey results indicated that these players had undergone at least 9 years of training and competitive experience. To ensure participant eligibility, the study adhered to exclusion criteria established in previous research [12–17]. As a result, 18.8% of potential participants were excluded based on the following conditions: (1) inability to complete the entire experiment; (2) injuries such as ligament tears or lower limb dislocations within the past 6 months; (3) documented history of fractures or surgeries, as verified by hospital certificates; (4) long-term professional training in sports other than squash; (5) body mass index (BMI) outside the World Health Organization and Asia-Pacific recommended range of 18.5 to 23.9 years; and (6) records provided by athletic trainers or coaches indicating bone, joint, or neuropathic injuries to the lower limbs sustained during training or competition. Similarly, participants in the control group were selected from 40 male collegiate students who met the same eligibility criteria. These students were undergraduates from the same institutions as the squash players.

Prior to the start of the experiment, all participants voluntarily provided written informed consent after being thoroughly briefed by the researchers on the study’s objectives, procedures, and requirements. At the outset of the study, participants’ age, height, weight and BMI, as well as their training and competition experience were documented. Anthropometric data for the eligible participants were subsequently collected after the experiment and are presented in Table 1.

INSTRUMENTATION:

In this study, an optical plantar pressure analyzer combined with the built-in FPDS-Pro-V.2 program (JC Mat; sampling frequency: 15 Hz; sensitivity: 25 sensors per side within the measurement area of 32×17 cm; View Grand International Co, Ltd, Taiwan) was used to record plantar pressure values across different regions of each participant’s foot during the experimental procedures. Prior to data collection, the device’s pressure linearity was calibrated following standardized protocols established in previous studies, to ensure measurement accuracy and consistency [12–17,22–24]. The JC Mat analyzer operates in conjunction with an external notebook computer, facilitating the acquisition of color-coded footprint images during both static standing and dynamic walking tasks without spatial or temporal constraints. Additionally, the FPDS-Pro-V.2 program supports the analysis of key parameters relevant to this study, including the PLD, FAI, and the center of gravity for each recorded footprint image.

PLANTAR LOAD MEASUREMENT AND ANALYSIS:

The study was conducted outside of the competition period of the squash championships during the academic years of the University in Taiwan. All experimental procedures were systematically scheduled in the afternoon on the participants’ campus, to ensure consistency. Prior to the commencement of the study, informed consent was obtained from each participant to ensure voluntary participation throughout the research process, and their demographic characteristics were thoroughly documented. To minimize external variables, the feet of all elite squash players were measured uniformly either 3 days before or after competitions or training sessions. The measurements were performed under controlled conditions, with researchers supervising and guiding each participant through the entire process. The standardized measurement protocol using the JC Mat optical plantar pressure analyzer was as follows. (1) Each participant received comprehensive instructions from the same researcher to ensure consistency in measuring the preliminary dataset of plantar load distribution. (2) Participants were required to wear short sportswear and stand barefoot on the sensor mat, which was marked with specific indicators and measurement ranges for the JC Mat. (3) They were instructed to maintain a relaxed and stable static standing posture. During the measurement process, participants were asked to adopt their most comfortable and natural stance until the foot pressure readings detected by the device stabilized without significant fluctuations. (4) At this point, the JC Mat immediately recorded the pressure profiles of the static footprints. Subsequently, researchers used the integrated FPDS-Pro-V.2 program on the JC Mat to derive various parameters from the participants’ authentic barefoot footprints, including FAI, PLD, and center of gravity, all correlated with the color-coded footprint images. (5) After completing the measurements, the same researcher conducted an assessment of rearfoot postural alignment at the same location. The entire experimental process required approximately 20 min per participant [12–17,22,23].

During the subsequent data analysis, the researcher used the software to identify and connect 2 fixed reference points on each collected footprint image: the base of the second toe and the central base of the heel. The software then automatically segmented the footprint image (excluding the toes) into 6 equal-area subregions, each corresponding to specific anatomical structures of the foot. Based on prior research, these 6 subregions, arranged from anteromedial to posterolateral, were defined as the medial metatarsal, lateral metatarsal, medial longitudinal arch, lateral longitudinal arch, medial heel, and lateral heel. Furthermore, the forefoot region included the medial metatarsal and lateral metatarsal, the midfoot region included the medial longitudinal arch and lateral longitudinal arch, and the rearfoot region included the medial heel and lateral heel. The lateral foot region was defined by the lateral metatarsal, lateral longitudinal arch, and lateral heel, while the medial foot region consisted of the medial metatarsal, medial longitudinal arch, and medial heel. For each subregion, the software calculated the area occupied and the plantar load borne by the footprint image. Additionally, the FAI was estimated using the formula proposed by Cavanagh and Rodgers, which calculates the ratio of the midfoot area to the total footprint area (including the forefoot, midfoot, and rearfoot), while excluding the toes [25]. The PLD for the 6 subregions, as well as the center of gravity for both feet, were also determined based on the loads recorded in these subregions [12–17,22,23].

REARFOOT POSTURAL ALIGNMENT ASSESSMENT AND ANALYSIS:

To assess rearfoot pronation and supination behavior, participants were instructed to stand upright on a 30-cm high platform with their feet naturally spaced approximately 12 to 15 cm apart. Once the participants were stable on the platform, it was ensured that the rearfoot of both feet was aligned on the same horizontal plane. At this point, the researcher used a fixed-point digital camera to capture images of each participant’s rearfoot posture from a posterior perspective. Subsequently, the Biomech 2019 postural analysis software (Loran Engineering SrL, Emilia-Romagna, Italy; sampling frequency of 100 Hz) was used to calculate the rearfoot static angle by connecting 3 anatomical points identified in the digital photographs. These landmarks, listed from inferior to superior, included (1) the posterior calcaneal tuberosity, (2) a point above the center of the calcaneus, and (3) the lower third of the leg. After marking these points, the software automatically generated a standard straight line (solid line) representing the lower extremity, extending from the lower third of the leg to the center of the calcaneus. Additionally, a second line (dotted line), referred to as the flip angle line, was drawn from the posterior tubercle of the calcaneus to the center of the calcaneus. The intersection of these 2 lines defined the flip angle, which was used to classify calcaneal angles as normal (0° to 5°), varus (<0°), or valgus (>5°) [12,15,22,23].

SAMPLE SIZE ESTIMATION:

The sample size estimation was performed using a priori power analysis software (G*Power version 3.1.9.7, Universität Düsseldorf, Düsseldorf, Germany). For the effect size, Cohen’s d was calculated through the mean±standard deviation (SD) of the center of gravity values of the groups (control group: 51.36±5.57; squash group: 49.42±6.02), resulting in an effect size of 0.78. With the alpha error probability (significance level) for the independent sample t tests set at 0.05 and a desired statistical power (1-β) of 0.80, the minimum required sample sizes were determined to be 31 participants for the control group and 25 participants for the squash group.

STATISTICAL ANALYSIS:

This study had a cross-sectional design and used descriptive statistics to analyze the participants’ anthropometric data. The Shapiro-Wilk test was used to examine the normality of the data distribution and the homogeneity of variances, with P>0.05 indicating a normal distribution. Statistical analyses were conducted under the assumption of normality, with results reported as either mean±SD for normally distributed data or median with interquartile range (IQR) for non-normally distributed data. Comparative statistical analyses between the 2 groups were performed using the independent sample t test for normally distributed data or the Mann-Whitney U test for non-normally distributed data. A significance level of P<0.05 was established for all statistical determinations. All analyses were executed by a single researcher, using SPSS software (version 27.0, IBM Corp, Armonk, NY, USA) for Windows operating system.

Results

FOOT ARCH INDEX ASSESSMENT:

The results showed that the participants in both groups had symmetrical FAI values, with no significant differences observed between the feet within each group. The static FAI for each group was within the normal range (Table 2), suggesting that the participants could be classified as having normal arches.

PLANTAR LOAD DISTRIBUTION ASSESSMENT:

The PLD in elite squash players exhibited significantly higher loads on the left forefoot (23.93±6.96, P=0.001) and right midfoot (12.13±12.31, P=0.004), while experiencing lower loads on the bipedal lateral foot (left: 20.71%±7.54%, P=0.002; right: 21.18%±7.51%, P=0.027) than the control group (Table 3). An analysis of the 6 subregions of the plantar surface of both feet revealed that the plantar loads in the squash group were symmetrically distributed. The load distributions at the medial metatarsals (left: 23.68%±7.74%, P=0.005; right: 21.64%±7.73%, P=0.040) and lateral longitudinal arches (left: 20.49%±9.11%, P=0.000; right: 23.20%±7.33%, P=0.047) of both feet of the squash group were more symmetrical than those of the control group, whereas the loads at the lateral metatarsals (left: 24.18%±6.22%, P=0.005; right: 23.37%±8.07%, P=0.003) and lateral heels (left: 17.47%±5.45%, P=0.040; right: 16.96%±5.22%, P=0.041) were comparatively lower (Figure 1). This loading pattern indicated that static plantar loads in elite squash players are primarily concentrated in the forefoot and midfoot regions.

CENTER OF GRAVITY ASSESSMENT:

The results showed that the participants in both groups exhibited symmetrical center of gravity, with no significant differences observed between the groups. Additionally, there were no notable differences in the center of gravity of both feet within each group (Table 4).

REARFOOT POSTURAL ALIGNMENT ASSESSMENT:

The findings showed that the calcaneal angles of both feet in the groups were symmetrical and fell within the normal range of 0° to 5°. No significant differences were observed between the feet of participants within each group. Furthermore, the calcaneal angles of participants in the squash group (left: 2.63°±3.42°, P=0.000; right: 2.57°±3.46°, P=0.000) were significantly greater than those of the control group (Table 5). These results suggest that elite squash players had increased calcaneal valgus angles.

FOOTPRINT IMAGE CHARACTERISTICS ANALYSIS:

The footprint image for a representative participant from each group was determined by averaging the PLD across all participants within each group. A significant concentration of plantar loads was observed at the medial metatarsals and lateral longitudinal arches of both feet in the squash group, compared with that of the control group (Figure 2).

Discussion

The primary findings of the study are as follows. (1) The static FAI of both feet in each group was symmetrical and within the normal range, with no statistically significant differences observed between the groups. (2) The squash group exhibited symmetrical increases in PLD at the medial metatarsals and lateral longitudinal arches of both feet. From an overall perspective, the plantar loads were predominantly concentrated in the left forefoot and right midfoot regions. (3) Elite squash players maintained a symmetrical center of gravity on both feet during static stance. Finally, (4) the static rearfoot angles of both feet in each group were symmetrical and in a neutral position, while the valgus angles in the squash group were significantly greater than those in the control group.

Consistent with previous studies on elite table tennis and badminton players [13,14], the present study showed that the FAI of elite squash players aligns with the normal arch patterns observed in other racquet sport athletes [12]. A recent study by Sedaghati et al showed that individuals with normal arches exhibit superior postural control, compared with those with high arches or flatfoot deformities [26]. Similarly, Rdzanek and Wychowański reported that individuals with well-formed arches are more adept at maintaining balance during bipedal standing [27]. Huang et al reported no significant asymmetry in PLD between the left and right feet of badminton players [7]. These findings echo our previous research on elite table tennis players [13], collectively reinforcing the results of the present study, which demonstrate that elite squash players exhibit symmetrical and well-balanced centers of gravity on both feet [7].

Regarding the findings on PLD, elite squash players exhibited symmetrical loading patterns across the medial metatarsals and lateral longitudinal arches of both feet. From the perspective of the 5 plantar regions, it was observed that the forefoot and midfoot regions had higher load distributions, while the lateral regions had relatively lower load distributions than did the medial regions. This loading pattern partially supports our hypothesis and aligns with findings from other studies on racquet sports, which indicate that athletes predominantly concentrate their plantar loads in the forefoot and midfoot regions [5,28]. Similarly, as previously noted in elite table tennis players, their plantar loads during static standing were symmetrically distributed across the lateral metatarsals of both feet [13]. He et al observed that during dynamic movements in table tennis, players experience greater force loading on the forefoot than on the rearfoot, which they posited was necessary to maintain the ankle in a plantar flexion position [29]. Also, Zhao and Li demonstrated that professional badminton players exhibited significantly greater forefoot loading, particularly in terms of the pressure-time integral at the first metatarsal head, than did amateur players during the execution of a backcourt forehand clear stroke [30]. Huang et al reported significant increases in peak pressure, pressure-time integral, and contact area at the hallux, as well as the medial and lateral heels of badminton players while walking [7]. This pronounced forefoot loading pattern agrees with earlier findings by West et al, who suggested that squash players, skiers, and dancers are at an elevated risk of developing acute metatarsal bursitis at the first metatarsal and chronic inflammatory arthritis affecting the second to fourth metatarsals [31]. Notably, Aboriginal Australians exhibit similar foot characteristics. Research by Charles indicates that while Aboriginal Australians possess superior physical fitness and athletic ability, they also demonstrate higher peak pressure around the first to third metatarsal heads and the big toe, alongside elevated peak pressure and/or higher pressure-time integral in the midfoot [32]. Increased peak pressure in the midfoot has been associated with a higher incidence of knee and back injuries [32]. Excessive forefoot loading tends to prolong and intensify weight-bearing on the forefoot, which can diminish the range of motion of the ankle, potentially leading to conditions such as plantar fasciitis, Achilles tendinitis, and midfoot arthritis [33]. The metatarsals serve as the primary structural components of the forefoot, fulfilling critical roles in load-bearing and maintaining the body’s center of gravity. They are pivotal in providing support and facilitating propulsion of the foot and ankle during movement [13]. Prolonged engagement in long-distance running has been shown to alter foot kinematics, leading to a redistribution of plantar loads across the forefoot. Specifically, this redistribution often results in increased pressure beneath the medial metatarsals and decreased pressure beneath the lateral metatarsals, potentially contributing to the development of a more pronated foot posture from an initial midfoot strike pattern [34]. Furthermore, research suggests that during extended running, the dynamic functionality of the toes diminishes over time. This is evidenced by a progressive shift in loading and plantar temperature from the hallux to the medial metatarsal regions [35,36]. Also, in a retrospective study on the biomechanics of long-distance running, Kim et al reported that runners’ feet tend to shift their landing technique from a heel-toe to midfoot landing strategy due to the need to compensate for local muscle fatigue after long-distance running [37].

As for the results of rearfoot postural alignment analysis, although the calcaneal angles of both feet in elite squash players fell within the neutral range, the mean values were significantly different than those of the control group. These findings are somewhat consistent with those reported by Huang et al, who found that the mean foot posture index values for male and female badminton players were 5.2±1.95 and 5.7±1.15, respectively, while those for individuals who do not regularly play badminton were 1.5±1.73 and 1.7±4.16. This indicates that regular badminton players tend to exhibit a higher degree of foot pronation [7]. Furthermore, a recent study by Christina highlighted that athletes in squash, karate, and baseball are more susceptible to foot pronation than is the general population [38]. It is important to note that foot pronation is a natural component of gait and plays a crucial role in executing dynamic tasks, such as running [39]. Pronation not only facilitates shock absorption, aiding the foot in adapting to ground surfaces and preventing excessive loading on the lower limbs, but also contributes to the locking of the tarsal joints, allowing the foot to function as a rigid lever during the late stance phase [40–42]. Additionally, pronation helps to unlock the midtarsal joints, enhancing the flexibility and pliability of the forefoot during various activities [43]. Regarding the relationship between pronated foot and PLD, previous research has suggested that pronation can help evenly distribute loads across the various anatomical structures of the foot and leg during initial exercise training, thereby preventing excessive stress on specific structures [44]. Conversely, a pronated foot can also diminish postural stability and elevate the risk of sports injuries. For instance, as noted earlier, professional soccer players with pronated feet have an increased risk of hamstring and medial collateral ligament injuries, resulting in greater time lost due to lower extremity injuries [20]. Additionally, foot pronation can lead to misalignment in the lower extremities, primarily caused by excessive internal rotation of the tibia and hip during activities such as walking and running [45]. This misalignment can further heighten the susceptibility to musculoskeletal injuries [46], emphasizing the necessity of addressing foot posture in injury prevention strategies.

This study aims to provide preliminary insights into the foot characteristics of elite Taiwanese squash players and to elucidate commonalities in PLD and foot postural characteristics across different racquet sports. The findings can contribute to future research exploring potential correlations between PLD and foot posture developed through long-term engagement in squash and the occurrence of musculoskeletal injuries in specific areas of the lower limbs. Ultimately, these findings can serve as a basis for designing or improving squash-specific footwear, such as footwear with metatarsal pads or optimized longitudinal bending stiffness, to evaluate whether impact forces can be distributed more evenly, or if peak impact forces can be dissipated. Additionally, this study can serve as a reference for future research topics concerning the functional comparison of footwear among squash, badminton, and tennis shoes. However, this study is subject to several limitations. First, it primarily used targeted sampling based on participants’ age, BMI, squash-specific training, and competition experience. Furthermore, the limited number of professional squash players in Taiwan, coupled with the predominance of male participants, has resulted in a constrained sample size for this research. A study conducted by He et al indicated that the performance of racket acceleration and maximum swing acceleration influenced by lower limb biomechanics can differ due to gender factors [47]. Consequently, the findings of this study may not be generalizable to female athletes, thereby limiting the broader interpretation of the effects of this sport on foot characteristics. Second, this study is characterized as a cross-sectional investigation that primarily examines the outcomes of long-term training and competition experience on the static PLD and foot posture of elite squash athletes. As a result, it is inherently limited in its ability to track how participants’ foot characteristics evolve over time with prolonged training, thereby restricting the inference of dynamic changes throughout the training process. Third, the application of the JC Mat optical plantar pressure analyzer in this study differs from the footwear-type pressure sensors used in other research, which limits the ability to draw direct and effective comparisons with other sports or methodologies. Finally, this study cannot avoid the limitation of insufficiently accounting for external factors, such as participants’ daily lifestyles, that can influence PLD and foot posture. Despite these inherent limitations, the study draws upon several examples from various racquet sports for comparison with squash players. Future research can build upon the findings of this study regarding static plantar load and foot posture characteristics to further elucidate the complex relationships among dynamic foot and lower limb biomechanics, training programs, and injury prevention strategies related to squash. Ultimately, this will aid in the development of optimized footwear and training prescriptions tailored to the unique demands of this sport.

Conclusions

This study on elite collegiate squash players in Taiwan showed that their feet displayed normal and symmetrical FAI, center of gravity, and rearfoot postural alignment. Increased plantar loads were noted at the medial metatarsals and lateral longitudinal arches, while a decrease in load occurred on the lateral aspect of the foot after prolonged squash training and competition. These results highlight the distinct foot characteristics of squash players, compared with those in other racquet sports, offering a foundation for future research on biomechanical implications and the development of specialized footwear to optimize load distribution and reduce injury risk.