Biomechanical Adaptations in Foot Characteristics Among Elite Male Weightlifters: A Cross-Sectional Comparative Study

Introduction

In the discipline of weightlifting, the snatch and the clean and jerk constitute the 2 fundamental competitive lifts in which athletes endeavor to elevate maximal poundage for a single repetition [1]. The snatch consists of initiating the lift from a squatting posture and executing a singular, explosive movement to propel the barbell overhead, while the clean and jerk is a biphasic lift, involving an initial movement to raise the barbell to the chest, followed by a subsequent action to hoist it overhead [2]. Both maneuvers demand exceptional coordination and meticulous technique throughout their execution [3]. An examination of weightlifting world records indicates that weightlifters frequently lift loads that are 2 to 3 times their body weight during these lifts [4]. The function of the feet is particularly critical in weightlifting, as they provide a dynamic support base throughout the lifting process, playing an essential role in achieving optimal technical performance [5]. Consequently, elite weightlifters must meet extremely high biomechanical demands and exhibit advanced neuromuscular control throughout these maneuvers, to optimize force transfer and maintain movement stability [6,7].

The research of Hawrylak and Gronowska underscores that the distribution of plantar pressure and foot contact area are critical determinants for optimizing technical performance and training outcomes in weightlifting [2]. Their study, which included 24 national-level competitive weightlifters and 24 physical education students, revealed that under static conditions, the highest plantar pressure was concentrated in the rearfoot of the dominant limb in both groups. Conversely, dynamic lifting phases induced a pressure shift, with both cohorts demonstrating increased pressure concentrations in the forefoot region. Furthermore, the highest average plantar pressure was consistently recorded in the rearfoot of the non-dominant limb across all participants, a phenomenon potentially attributable to the functional shortening of the superficial dorsal line, imbalances in muscular tension across the plantar surface, or contractures of the hamstring musculature. These findings highlight the importance of proper foot placement in both the starting position and subsequent phases of the lift, for maximizing force generation, ensuring stability, and achieving efficient movement execution [2]. While several studies have examined squat techniques as a means of improving lower limb strength in weightlifters [8], there is a notable lack of research investigating the effects of weightlifting on the foot structure and distribution of plantar load among athletes [2]. Understanding these fundamental factors is essential for improving biomechanical efficiency, neuromuscular coordination, and load management throughout the lift, which could lead to the development of more effective training strategies and injury prevention measures for athletes [5,7,9,10].

Previous research has shown that even amateur participation in strength sports can induce morphological changes in foot structure [11]. The feet serve as the foundational element of the lower limb kinetic chain. In addition to functioning as shock absorbers, load-bearing structures, and movement facilitators, they also resist deformation, provide stability, and act as levers to improve propulsion efficiency [12]. Evaluating their functional status both in static and dynamic conditions is essential for identifying asymmetries or deficiencies within an individual’s biomechanical system [13]. Abnormal foot structures can lead to uneven plantar pressure distribution across the sole, thereby compromising stability during lifting maneuvers and increasing the risk of injury to the foot and lower limbs [2,14]. For instance, excessive pressure on the forefoot or heel can result in localized injuries, such as metatarsalgia or plantar fasciitis, particularly under the repetitive and high-intensity loading conditions associated with weightlifting [14]. Research conducted by Pangan and Leineweber indicated that the use of weightlifting shoes significantly enhances the ankle plantarflexion angle while simultaneously reducing trunk lean, thereby effectively redistributing the load across the foot [15]. Additionally, the study highlighted that the practice of elevating the heel with external squat wedges has emerged as a widely adopted rehabilitation technique, which has been shown to yield effects comparable to those achieved with weightlifting shoes. This biomechanical adjustment enhances the activation of the knee extensor, reducing shear forces and mitigating excessive loading on the lumbar spine [16,17]. This interconnected mechanism illustrates how the structural and functional characteristics of the foot directly influence the alignment of the musculoskeletal system, movement efficiency, stability, and susceptibility to injury [18,19]. It underscores the critical role of foot anatomy and biomechanics in optimizing weightlifting performance and minimizing injury risks, highlighting the importance of conducting systematic evaluations of athletes’ foot biomechanics.

Foot posture is intricately linked to weightlifting performance and injury susceptibility [20]. Specifically, rearfoot valgus, a prevalent feature of pronated foot posture, has been demonstrated to augment medial knee contact forces during barbell squats [20] and to increase stress on the plantar fascia [21]. Excessive pronation imposes additional loading on the knee joint, potentially contributing to conditions such as bunions, plantar fasciitis, and heel pain. Such repetitive weight-bearing scenarios are particularly prevalent among weightlifters, resulting in inefficient force transfer and heightened injury risk during lifts such as squats and deadlifts [20,21]. Moreover, abnormal foot posture can disrupt neuromuscular control, resulting in asymmetrical loading patterns during weightlifting. This asymmetry elevates the likelihood of chronic injuries, including iliotibial band syndrome or femoroacetabular impingement, stemming from recurrent strain on specific anatomical structures [14]. Similarly, Hawrylak and Gronowska further found that most weightlifters presented with a neutral pronation foot posture, with only a small proportion exhibiting excessive pronation [2]. The mean calcaneal angle and plantar axis were found to be greatest in the weightlifting cohort for the dominant limb under static conditions [2]. Neutral pronation was the predominant foot posture in both the weightlifting and control groups, a finding consistent with research by Gómez et al [22]. This prevalence might be attributable to the appropriate development of the lateral line of the fascia among most participants [22]. Excessive foot valgus can precipitate knee valgus [23], which increases pressure on the anterior cruciate ligament and results in injury [24]. Consequently, these findings underscore the biomechanical importance of foot posture in weightlifting, revealing a clear association between deviations from neutral alignment and an increased risk of lower-extremity injuries. They further emphasize the necessity of systematically evaluating and considering foot postural alignment within training regimens and injury-prevention strategies [25].

Given the critical role of foot biomechanics in weightlifting performance and injury prevention, previous studies have indicated that high-intensity weightlifting can lead to adaptive changes in the structure and function of the musculoskeletal system [2]. However, comprehensive research on the foot characteristics of weightlifters remains limited. In this study, we aimed to address this gap by comparing the foot arch index (FAI), plantar load distribution (PLD), center of pressure (CoP), and rearfoot posture between 24 elite male weightlifters (77 kg and 85 kg weight classes) and a control group of 32 age- and body mass index (BMI)-matched healthy men. It is hypothesized that elite weightlifters may develop distinctive foot structures characterized by lower arches or flat feet, more commonly than does the general population. These structural adaptations can result in increased PLD in the rearfoot or medial foot, accompanied by a rearfoot valgus posture. Considering that weightlifting involves a bilateral synchronous and equal load-bearing movement pattern, it is further hypothesized that the plantar load and CoP distribution between the left and right feet can exhibit symmetry. The findings of this study are expected to provide a detailed characterization of the foot structure and PLD patterns of weightlifters in their daily lives, thereby offering critical insights into their biomechanical characteristics. Understanding these biomechanical adaptations is essential for optimizing athletic performance, preventing injuries, and guiding the design of weightlifting-specific footwear.

Material and Methods

ETHICS STATEMENT:

This research was conducted in strict adherence to the ethical principles established by the Declaration of Helsinki and its subsequent amendments. The study received approval from the Research Ethics Committee of National Taiwan University, Taipei City, Taiwan, which granted clearance for the research protocol (NTU-REC No.: 201506 ES016). Prior to participation, all participants provided written informed consent after being thoroughly informed about the study’s objectives, methodologies, and requirements.

PARTICIPANTS:

The cross-sectional survey was conducted over a total duration of 26 months, encompassing participant recruitment, experimental implementation, and subsequent data augmentation and analysis at multiple university facilities in Taiwan. A total of 56 healthy Taiwanese male university students were recruited for the study, consisting of 24 elite weightlifters competing in the 77 kg and 85 kg weight classes (weightlifting group) and 32 age-matched undergraduates with no prior experience in weightlifting or other specialized sports (control group). The weightlifting group had a mean age of 23 years (20–24 years), mean height of 176.0 cm (168.0–180.0 cm), and mean weight of 83.7 kg (75.6–85.0 kg). In contrast, the control group had a mean age of 22 years (20–23 years), mean height of 175.5 cm (168.0–180.0 cm), and mean weight of 82.5 kg (75.3–85.0 kg). Due to the weight-class requirements for weightlifting, the number of qualified and eligible weightlifters available for recruitment was limited. These 24 qualified weightlifters were selected from 29 male athletes who had competed in the men’s open division at the National Intercollegiate Athletic Games in Taiwan. All selected weightlifters were identified as right-handed, with their dominant limb as their lifting arm. They also reported having a minimum of 5 years of systematic training and competition experience.

To ensure participant eligibility, this study adhered to the exclusion criteria established in previous research [26–28]. Consequently, 17.2% of potential participants were excluded based on the following criteria: (1) weightlifters in weight classes other than 77 kg or 85 kg; (2) inability to fully participate in the entire experimental protocol; (3) history of ligament tears or lower limb dislocations within the past 6 months; (4) a previous history of fractures or surgical interventions in lower limbs; (5) long-term professional training in sports other than weightlifting; (6) documented lower limb skeletal, joint, or neurological injuries confirmed by a coach or trainer; or (7) current acute injuries or pain affecting gait or standing posture. Since all weightlifting participants had a BMI exceeding the normal adult range defined by the World Health Organization and the Asia-Pacific guidelines (18.5–23.9 kg/m2), the control group participants were selected from 45 male students who met the aforementioned screening criteria and had BMI values comparable to those of the weightlifting group (26.1–27.2 kg/m2). To minimize potential bias, a single-blind design was used for group assignment, thereby ensuring that all participants were unaware of their group allocation. This was primarily to prevent any influence on their responses or behaviors during the study. Specifically, only the researchers responsible for conducting the assessments were aware of the group allocations, as they needed to document participants’ training and competition experiences. All assessments strictly followed standardized protocols, including the use of validated instruments (eg, the JC Mat optical plantar pressure analyzer) and predefined data collection standards. Prior to enrollment in the study, all participants were thoroughly informed by the researchers about the study’s objectives and experimental procedures. Subsequently, each participant voluntarily signed a written informed consent form. At the commencement of the study, basic demographic data and anthropometric measurements, including age, height, weight, BMI, and training history, were recorded. Fundamental anthropometric characteristics were recorded after the experiment and are presented in Table 1.

INSTRUMENTS:

This study used the JC Mat optical plantar pressure analyzer (View Grand International Co, Ltd, New Taipei City, Taiwan), which processed the data at a sampling frequency of 15 Hz during static standing trials. The reproducibility and reliability of this device had been rigorously validated in previous research, and its technical specifications and operational methodologies had also been extensively documented in those studies [26–28]. The analyzer’s integrated FPDS-Pro-V.3.0 software enabled the direct transformation of participants’ barefoot pressure measurements into color-coded footprint images. These images allowed for the extraction of multiple critical parameters associated with foot characteristics and biomechanics, including the bipedal FAI, PLD, CoP, hallux angle, foot dimensions, and line of travel. Furthermore, the pressure curve visualization offered a detailed depiction of load distribution across various plantar regions, thereby providing enhanced clarity in data interpretation.

EXPERIMENTAL PROCEDURES:

To ensure consistency and reliability throughout the experimental procedures, participants in the weightlifting group underwent measurements during their non-training and non-competition periods at their respective schools. To accommodate the majority of participants’ availability outside of class hours, measurement sessions for both groups were uniformly scheduled on Thursday or Friday afternoons between 2: 00 PM and 4: 00 PM. The experimental protocol began with static plantar load measurements, followed by rearfoot postural assessments. Each participant required approximately 20 min to complete the entire experimental process. All foot-related parameters, including FAI, PLD, CoP, and rearfoot posture, were analyzed and determined by the same researcher.

FAI, PLD, AND COP MEASUREMENTS AND ANALYSES:

The primary parameters, including the FAI, PLD, and CoP, were concurrently assessed using the JC Mat optical plantar pressure analyzer while participants maintained a static standing posture. The measurement protocols were primarily based on standardized operational guidelines established in previous research [26–28]. Specifically, the FAI serves as a quantitative indicator of medial longitudinal arch height within the foot structure, making it an effective tool for assessing foot structural characteristics. PLD represents the spatial pattern of pressure distribution across various regions of the plantar surface during weight-bearing activities, thereby facilitating a comprehensive understanding of foot functional mechanics and potential compensatory loading patterns that can develop in response to training adaptations. CoP provides an overall perspective of bilateral PLD, reflecting postural control, bilateral symmetry, and balance stability between both feet during static or dynamic conditions.

During the measurement, participants were instructed to wear shorts and practice barefoot stepping in place on the JC Mat, which featured specific markings and a defined measuring range, prior to stabilizing their stance. Once familiarized with the procedure, participants were formally guided to stand on the JC Mat for measurement. Following the researcher’s instructions, participants were asked to look straight ahead, perform 6 to 8 steps in place with a natural gait, and then assume a natural standing posture, with arms relaxed at their sides and feet shoulder-width apart. They were instructed to maintain stability and avoid body movement while engaging their core and controlling their center of gravity. Once the JC Mat detected stable foot pressure readings, typically occurring after approximately 6 s, it automatically recorded the pressure curve of the static footprints. After completing the measurements, the built-in FPDS-Pro-V.3.0 software calculated the aforementioned key parameters based on the captured footprint images of each participant.

During the analysis procedures, the researcher initially identified and marked 2 specific anatomical landmarks on the color footprint images of each participant displayed on the computer screen: the base of the second toe and the center of the heel. Once these points were confirmed, the built-in FPDS-Pro-V.3.0 software automatically generated a straight line along with 4 perpendicular parallel tangents. These tangents were positioned between the 2 landmark points and encompassed the entire footprint image, excluding the toes. Consequently, the footprint image was subdivided into 6 subregions by these equal-area tangents. These subregions were defined from the anterior medial to the posterior lateral as follows: (1) medial metatarsal, (2) medial longitudinal arch, (3) medial heel, (4) lateral metatarsal, (5) lateral longitudinal arch, and (6) lateral heel. Furthermore, these subregions could be combined with adjacent subregions to form a total of 5 distinct regions: (A) forefoot region (including lateral metatarsal and medial metatarsal), (B) midfoot region (lateral longitudinal arch and medial longitudinal arch), (C) rearfoot region (lateral heel and medial heel), (D) lateral foot region (lateral metatarsal, lateral longitudinal arch, and lateral heel), and (E) medial foot region (medial metatarsal, medial longitudinal arch, and medial heel). Within these 5 regions, the FAI value was calculated according to the definition provided by Cavanagh and Rodgers [29], representing the ratio of the midfoot region (denoted as B) to the total footprint excluding the toes (denoted as A+B+C), expressed as FAI=B/(A+B+C). Based on established thresholds, a normal arch corresponds to FAI values between 0.21 and 0.26, a high arch to FAI values below 0.21, and a low arch to FAI values above 0.26.

The assessment of CoP parameters was primarily based on the percentage of pressure distribution between the entire left and right feet of participants during the static standing measurement. According to established standards, the total pressure distribution for both feet is expressed as a percentage (left foot%+right foot%=100%), with normal balance defined as 50%±5% for each foot.

REARFOOT POSTURAL MEASUREMENTS AND ANALYSES:

The second phase of the experiment focused on evaluating rearfoot posture, which is defined by rearfoot varus or valgus angles and serves as a critical parameter for understanding biomechanical adaptations induced by athletic activities, serving as an important reference indicator for athletic performance and potential injury risk in athletes. The measurement procedures were strictly followed by the standardized operational protocols outlined in prior studies [26–28]. During the assessment, participants were instructed by the researcher to adopt a stable, upright stance on a 30-cm-high platform. Their feet were positioned naturally, spaced approximately 12 to 15 cm apart, ensuring that the rearfoot was aligned on the same horizontal plane. Rearfoot posture images of each participant were captured from a posterior perspective using a stationary digital camera and subsequently analyzed with Biomech 2019 posture analysis software (Loran Engineering SrL, Emilia-Romagna, Italy), which processed the data at a sampling frequency of 100 Hz.

Furthermore, the angles of rearfoot posture were evaluated using the software, which calculated static rearfoot angles from the digital images of each participant’s rearfoot posture based on 3 specific anatomical reference points on the lower limb. These anatomical landmarks, arranged from distal to proximal, included (1) the posterior calcaneal tuberosity, (2) a point located superior to the center of the calcaneus, and (3) the lower third of the leg. After marking these reference points, the software automatically generated 2 lines: the first, a reference line (solid line), connected the lower third of the leg to the center of the calcaneus; the second, an angular line (dashed line), extended from the posterior calcaneal tuberosity to the center of the calcaneus. The angle formed at the intersection of these 2 lines was used to categorize rearfoot posture into 3 classifications: neutral (0° to 5°), varus (<0°), or valgus (>5°) [30].

SAMPLE SIZE DETERMINATION:

The sample size for this study was prospectively determined via an a priori power analysis using G*Power software (version 3.1.9.7, Universität Düsseldorf, Düsseldorf, Germany) [31]. This calculation was predicated on the effect size (Cohen’s d), computed from the mean±standard deviation (SD) of the control group (48.91±4.52) and the weightlifting group (50.21±3.55). To ensure adequate statistical power, the analysis had a significance level (α) of 0.05, statistical power (1−β) of 0.80, and effect size of 0.80, appropriate for an independent samples t test. These parameters indicated a requisite minimum of 54 participants, with 31 allocated to the control group and 23 to the weightlifting group [32].

STATISTICAL ANALYSIS:

The experimental data were analyzed based on their distribution characteristics. Continuous variables were assessed for normality using the Shapiro-Wilk test, with P>0.05 indicating a normal distribution. For normally distributed data, results were presented as mean±SD, while non-normally distributed data were reported as median with interquartile range. Key parameters, including PLD and CoP, were expressed as percentages, and rearfoot angles were reported in degrees. Statistical significance was determined using thresholds of P<0.05 (denoted by *) and P<0.01 (denoted by **), indicating statistically significant differences between groups. Comparative analyses between the elite male weightlifter group and control group were conducted using independent samples t tests for normally distributed data and the Mann-Whitney U test for non-normally distributed data. The choice of statistical test was based on the results of the Shapiro-Wilk test, ensuring that the appropriate method was applied according to the data distribution. All statistical analyses were performed using SPSS statistical software (version 27.0; IBM Corp, Armonk, NY, USA), using the relevant functions for descriptive statistics, normality testing, and hypothesis testing.

Results

ASSESSMENT OF FAI:

The analysis indicated that the FAI values of participants within each group were consistent and symmetrical across both feet (Table 2). In contrast, intergroup comparisons revealed that participants in the weightlifting group exhibited significantly higher FAI values for both feet than did those in the control group (P<0.05). The results suggest that the group of weightlifters exhibited a lower arch type than did the control group.

ASSESSMENT OF PLD ACROSS 5 REGIONS:

The results showed that, compared with the control group, participants in the weightlifting group exhibited significantly higher PLD in the forefoot region of the right foot (P<0.01; Table 3). Conversely, a symmetrical reduction in plantar load was observed in the lateral regions of both feet (P<0.01).

ASSESSMENT OF PLD ACROSS 6 SUBREGIONS:

The distribution of plantar loads across 6 subregions was symmetrical between the left and right feet of participants in the weightlifting group (Figure 1). Specifically, compared with the control group, the weightlifting group exhibited significantly higher PLD under the lateral metatarsals (P<0.05), medial longitudinal arch (P<0.05), and medial heel (P<0.01) in both feet, as well as under the left medial metatarsals (P<0.05). The results indicate that plantar loads are predominantly distributed along the medial aspects of the feet.

ASSESSMENT OF COP:

The CoP values for both feet revealed that participants in each group exhibited comparable and symmetrical distribution patterns (Table 4). Furthermore, no significant intergroup differences were observed, suggesting that the weightlifting group exhibited bilateral CoP symmetry comparable to that of the control group.

ASSESSMENT OF REARFOOT ANGLES:

The findings showed that the rearfoot angles within each group were consistent and symmetrical across both feet (Table 5). Nevertheless, intergroup comparisons revealed that the weightlifting group exhibited significantly greater rearfoot angles (P<0.01) than the control group. The results suggest that the weightlifter group displayed a rearfoot postural alignment indicative of increased heel eversion.

CHARACTERISTICS OF FOOTPRINT IMAGES:

The representative footprint images of the groups were derived by calculating the average plantar load values across 6 defined subregions of each foot for all participants within the respective groups. Intergroup comparisons identified that the footprint characteristics in the weightlifting group illustrated that plantar loads were primarily distributed along the bipedal medial longitudinal arches, medial heels, and lateral metatarsals, as well as the left medial metatarsal (Figure 2).

Discussion

This cross-sectional study investigated the foot characteristics of elite male weightlifters in Taiwan. The findings revealed that elite weightlifters exhibited a low-arched pronated foot posture, characterized by significantly higher FAI values than those of age- and BMI-matched healthy male controls. Specifically, the weightlifters demonstrated a symmetrical PLD primarily concentrated on the lateral metatarsals, medial longitudinal arches, and medial heels of both feet. Additionally, the CoP was symmetrically distributed across both feet, indicating balanced postural control. Notably, the rearfoot angles of the weightlifters were significantly greater, suggesting a rearfoot valgus alignment. Given that both feet serve identical functions and exhibit similar movement patterns during weightlifting, this bilateral symmetry in load distribution aligns with the findings of the present study that elite weightlifters demonstrate symmetrical PLD and CoP patterns, which are crucial for achieving bilateral stability during lifting. This observation is consistent with the arguments proposed by Pirani and Azizi, who suggested that the symmetrical distribution of plantar pressure and force between the left and right feet in elite weightlifters is a predictable outcome [33]. Similarly, Memar and Noori reported comparable findings, noting that wrestlers, due to the absence of a dominant foot and the uniform movement patterns of both feet, exhibited nearly identical distributions of maximum force, peak pressure, contact area, and contact time between their left and right feet [34]. This bilateral symmetry in load distribution mentioned above further echoes the principles observed by Wei et al in their study of foot biomechanics in patients with bilateral clubfoot, emphasizing the importance of symmetrical plantar pressure distribution in maintaining functional balance and reducing the risk of asymmetric loading injuries, foot deformities development, and related complications [35].

The analysis of PLD across 6 subregions in elite weightlifters revealed that higher loads were symmetrically concentrated at the lateral metatarsals, medial longitudinal arches, and medial heels of both feet, as well as at the medial metatarsals of the left foot, compared with that of the control group. Examination of plantar load across 5 broader regions indicated a significant decrease in lateral load on both feet, while the load in the forefoot region of the right foot showed an increasing trend. This distribution pattern is consistent with the findings of Pirani and Azizi, who reported that elite weightlifters exhibit identical pressure distribution patterns in both feet, with increased pressure primarily concentrated in the metatarsal and midfoot regions. The highest pressure and contact times were localized to the third through fifth metatarsals of both feet [33]. Furthermore, a similar load distribution pattern was also observed in previous studies focusing on elite table tennis players, which found that athletes exhibited symmetrical PLD and an increasing trend in forefoot loading [28]. These findings suggest that activities with lower displacement demands on the lower limbs can require enhanced biomechanical coordination of forefoot loading patterns to optimize stability and support during performance. However, prolonged contact times in the forefoot can result from increased flexibility of the medial longitudinal arch and weakened ligaments in that region [36], suggesting a prevalent degree of flatfoot among athletes [33].

In contrast, sports with higher lower limb displacement demands, such as squash and badminton, have shown an increasing trend in symmetrical PLD at the medial metatarsals, lateral longitudinal arch, and lateral heel [26,37]. This contrast highlights the distinct biomechanical adaptations required by different sports: squash and badminton demand rapid directional changes and agile footwork, leading to a forefoot-lateral foot loading pattern, whereas weightlifting necessitates stable bilateral weight support, resulting in a medial loading pattern. Consequently, the findings of the present study reinforce Pangan and Leineweber’s perspective that the primary design objective of weightlifting shoes is to redistribute load from the rearfoot through the incorporation of external squat wedges [15]. This design not only compensates for the medial PLD but also mitigates bodily stress, thereby enhancing the effectiveness of force generation in the limbs.

Furthermore, the analysis of rearfoot angles revealed that weightlifter group exhibited a significantly increased rearfoot eversion angle in both feet, compared with the control group, with values exceeding the normative range for neutral feet. This indicates that weightlifters can be classified as having a rearfoot valgus foot type. Rearfoot valgus is a common characteristic associated with foot pronation. Research by Lu et al has demonstrated that this alteration in foot posture can lead to increased flexion angles at the ankle, knee, and hip joints during barbell squatting, thereby elevating medial knee contact forces. This effect is particularly pronounced under heavy loading conditions, which consequently increases the risk of degenerative changes or acute injuries [20]. The results of the present study are consistent with those of Hawrylak and Gronowska, who observed that the majority of 24 national-level competitive weightlifters exhibited a neutral pronated foot posture [2]. However, similar results were found in a previous study by Cote et al, which showed that weightlifters are prone to excessive foot internal rotation due to the repetitive loading during lifting, consequently increasing pressure on the plantar fascia and leading to conditions such as bursitis and heel pain [38]. This change can also be attributed to increased ankle joint flexibility resulting from long-term regular training, which could lead athletes to adopt a valgus foot posture to accommodate the increased dorsiflexion angle during squatting [39]. A kinematic study found that individuals with valgus feet exhibited significantly higher peak moments in foot pronation, ankle dorsiflexion, ankle abduction, knee adduction, knee external rotation, hip abduction, and hip extension, while knee extension moments were significantly lower than those in individuals with normal feet [20]. During weight-bearing activities, such as squats or the clean and jerk, foot pronation can cause the CoP to shift inward. This medial displacement increases the compressive forces on the medial compartment of the knee joint, which over time can lead to joint degeneration and conditions such as osteoarthritis [40]. Therefore, foot posture plays a pivotal role in determining weightlifting performance and injury susceptibility [25]. Variations from neutral alignment can lead to uneven plantar pressure distribution, thereby compromising stability and increasing the likelihood of lower limb injuries, as supported by existing research. Excessive pronation can disrupt lower limb alignment, making it difficult to maintain a stable support base. This can lead to inefficient force transmission and increase the risk of injury during weightlifting movements, such as squats and deadlifts [20,41]. Consequently, maintaining proper foot alignment and stability during weightlifting is essential for optimizing performance and mitigating injury risks.

The structural characteristics of the foot, including arch height and foot shape, significantly influence overall body balance and stability across various contexts, even among amateur participants in strength sports [11]. Notably, the findings reveal that elite weightlifters, despite exhibiting a low-arched foot type, demonstrate comparable and symmetrical CoP values in both feet. This outcome is consistent with that of previous research on the foot characteristics of indigenous populations in Taiwan, which found that male indigenous students, who are generally recognized for their excellent physical performance, often present with low arches while still exhibiting strong performance and effective CoP control [27]. These findings suggest that through extensive and specialized core training, these athletes have developed exceptional bilateral balance control capabilities to meet the demands of their sport skills. Isaka et al previously reported similar results, indicating that weightlifters exhibit greater symmetry than do football players [42]. This symmetry is crucial for facilitating balanced force production and minimizing the risk of injury during the weightlifting process [43].

We acknowledge several limitations of this study. First, the cross-sectional design focused exclusively on male weightlifters in the 77 kg and 85 kg categories, which limits the generalizability of the findings to other weight classes. This restriction was necessary to ensure a sufficient sample size while controlling for BMI-related influences on foot musculoskeletal alignment. Second, the study included only male participants, and the inherent differences in foot structure and strength performance between sexes mean the results may not be directly applicable to female weightlifters. Third, the cross-sectional nature of the study precludes causal inferences regarding whether the observed low-arched and pronated foot postures were due to elevated BMI or adaptations from weightlifting training. Fourth, the JC Mat optical plantar pressure analyzer, while validated for static measurements, does not capture dynamic foot biomechanics during weightlifting movements, which can differ significantly from static conditions. Similarly, the rearfoot postural analysis relied on static images, which may not reflect dynamic alignment during lifting. Future research should incorporate dynamic assessments and include diverse weight classes and both sexes to provide a more comprehensive understanding of foot biomechanics in weightlifting.

In summary, the foot characteristics identified in this study of male weightlifters in Taiwan can be characterized as a low-arched pronated foot posture, with plantar loads primarily concentrated on the medial aspect of both feet. In contrast to the general population with flat feet, a notable distinction found in this study was the higher load distribution at the lateral metatarsals among weightlifters. This distribution pattern may be interpreted as a compensatory mechanism by athletes to compensate for the excessive medial PLD resulting from their low arches and excessive rearfoot pronation. Consequently, this adaptation increases the load on the lateral forefoot, thereby maintaining foot stability and lower limb balance, which is crucial for effective bilateral balance control in weightlifting activities.

Conclusions

This study investigated the foot characteristics of elite male weightlifters in Taiwan, revealing a low-arched pronated foot posture with symmetrical PLD concentrated along the medial longitudinal arches, medial heels, and lateral metatarsals of both feet. The CoP was symmetrically distributed across both feet, reflecting adaptive changes in foot biomechanics due to specialized weight training. However, the observed increase in rearfoot valgus suggests a potential risk for lower limb injuries. These findings emphasize the importance of systematically evaluating foot biomechanics to optimize athletic performance, prevent injuries, and inform the design of weightlifting-specific footwear.