Interlimb asymmetries of lower limb isometric strength for predicting plantar fasciitis in male amateur marathon runners: a prospective cohort study

Abstract

Background

Plantar fasciitis (PF) is the third most common type of running-related injuries. However, there are few studies on the association between interlimb asymmetry of lower limb isometric strength and PF among marathon runners. The present study aims to investigate whether the interlimb asymmetry of lower limb isometric strength could predict PF in male amateur marathon runners.

Methods

172 male amateur marathon runners were tested for lower limb isometric strength using the MicroFet 3 muscle testing dynamometer and inclinometer. The interlimb asymmetry of the lower limb isometric strength were calculated. Subsequently, the subjects were followed up for 3-month to record the incidence of PF. Statistical analysis was performed using independent-sample t test, logistic regression analysis and receiver operating characteristic (ROC) curve analysis.

Results

During the 3-month follow-up, a total of 12 runners experienced PF. The results of logistic regression analysis showed that the interlimb asymmetry of hip abduction isometric strength was significantly correlated with PF development (OR = 3.646; 95%CI:1.193–11.148; P = 0.023). The ROC curve analysis revealed that the area under the ROC curve was 0.717 (95% CI: 0.544–0.889, P = 0.012), and the sensitivity and specificity of the interlimb asymmetry of the hip abduction isometric strength for diagnosing PF were 0.667 and 0.238, indicating good discrimination. In addition, the Hosmer-Lemeshow fitting test showed that the model has statistical significance (X² = 14.365, P = 0.001).

Conclusions

The interlimb asymmetry of hip abduction isometric strength was associated with a greater likelihood of developing PF, and interlimb asymmetry of hip abduction isometric strength greater than 32.5% was a significant risk factor for the development of PF in male amateur marathon runners. The risk of PF occurence increased by 3.646 times if the interlimb asymmetry of hip abduction isometric strength greater than 32.5%. For clinicians, it is suggested to pay attention to the balanced development of bilateral muscle strength in the process of PF rehabilitation treatment, and regard the improvement of the interlimb asymmetry of hip abduction isometric strength as one of the rehabilitation therapies. Moreover, for runners and coaches, it is suggested that they should appropriately add unilateral or bilateral strength training (such as side-lying hip abduction training, clamshell exercise, supine bridge, etc.) in the daily training to ensure the balanced development of hip abduction strength, so as to prevent the occurrence of PF.

Introduction

Running is one of the most popular types of physical activity worldwide [1]. Current literature suggests that running promotes many health benefits such as reducing risk factors for cardiovascular diseases, increasing cardiorespiratory capacity and improving mental health [2]. However, along with the well-documented health benefits of running, there is also a high prevalence of running-related injuries (RRIs). Epidemiological studies have shown that the incidence of RRIs was 69.8% [3]. The injuries in runners mainly focus on the knee and foot, including patellofemoral pain, iliotibial band syndrome and plantar fasciitis (PF). PF is a chronic degenerative disease caused by repeated high mechanical stress and biomechanical overuse, with typical symptoms of plantar heel pain [4]. A review concerning ankle and foot injuries in sports revealed that PF was the third most common type of RRIs, with an incidence of 7.9%, and the economic burden of PF has reached $376 million [5].

Numerous studies have investigated related risk factors that may lead to PF. Some studies found that people who are overweight (BMI > 25 kg/m²) or obese (BMI > 30 kg/m²) were 1.4 times more likely to develop PF than those with normal BMI [6]. Some studies have suggested that the abnormal shape of the foot directly affected the plantar fascia [7], and a cross-sectional study with a large sample found that high arched foot was significantly correlated with PF [8]. Some studies have suggested that excessive foot pronation during running led to the increase of plantar fascia tension, and repeated collision of the heel led to the compression of the plantar fat pad, which increased the load of plantar fascia [9]. In addition, a higher vertical load rate during running also increased the risk of developing PF [10]. Some studies have suggested that external foot muscles such as internal foot muscles, posterior tibialis muscles and peroneus longus played an important role in supporting the arch of the foot. Weak muscle strength may lead to excessive pressure load on non-contractile structures such as plantar fascia, which may induce PF [11].

In recent years, interlimb asymmetries of lower limb strength has attracted attention as a risk factor for running-related injuries, such as PF [12]. Since running belongs to periodic movements, damage to one limb indicates that one side of the body is exposed to a higher load or has a lower tolerance to the load. There is evidence that bilateral imbalances in strength, structure, or gait biomechanics may lead to an increased risk of injury on one side of the limb [13]. In fact, the interlimb asymmetries of lower limb strength widely exists among athletes in different sports and has been regarded as an important risk factor for sports injury screening and evaluation [14–17]. In the study on the difference between the two sides of runners’ lower limbs, Hanley found that the contact time of long-distance runners in the terminal phase showed significant bilateral asymmetry compared with the initial phase in the 10,000 m running process [18]. The reason is that fatigue caused by long-distance running may increase or exacerbate the asymmetry that is not originally obvious [19]. In addition, studies have also shown that during repeated periodic movements (such as running and cycling, etc.), the lower limbs play different roles. One limb provides stability and support, while the other limb provides propulsion and braking. The difference in the functions of the two limbs will greatly lead to the asymmetry in the functions or strength of the two limbs [20]. The human body’s ability to perform running relies on the intricate coordination of kinetic chain. Kinetic chain inefficiency occurs when there is a defect or disruption at any point within the chain, which affects the transfer of energy or force to nearby segments. The defect in the kinetic chain places additional demands on the remaining segments of the chain to compensate for the energy loss and may increase the risk of injury [21]. Muscle strength imbalance may potentially affect motor control, resulting in impaired movement patterns and affecting sport performance. Therefore, muscle strength balance is crucial for optimizing movement patterns and improving the efficiency and economy of motor output [22].

However, while some studies have reported a significant association between interlimb asymmetries of the lower limbs and the risk of developing PF, no studies have specifically targeted the risk of PF in amateur marathon runners. In addition, based on a previous epidemiological study, male runners are more likely to develop PF than female runners [23]. Therefore, the purpose of this prospective study was to examine the interlimb asymmetries of lower limb isometric strength in male amateur marathon runners and investigate the relationship between difference and PF, in order to provide theoretical support and practical guidance in injury prevention of male amateur marathon runners. It was hypothesized that the interlimb asymmetry of lower limb isometric strength, especially the interlimb asymmetry of the hip abduction isometric strength was greater than 32.5%, could predict PF in male amateur marathon runners.

Methods

Study design

The sample size was determined via G*Power software (v3.1.9.2, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). Odds ratio was set at 3.47 (Medium effect size), Pr(Y = 1|X = 1)H0 was set at 0.15, αwas set at 0.05, power was set at 0.95, yielding a necessary sample size of 61. We ultimately recruited a total of 177 initially uninjured male amateur marathon runners. All subjects were recruited through wechat group, blog and other social communications platforms from universities and running clubs. This study was a prospective longitudinal observational trial that examined the risk factors for PF during a 3-month observational period. The basic information of the subjects was shown in Table 1. Before participation, all participants were required to complete a written informed consent form and a health history screening. All protocols and procedures were approved by the ethics committee of the Department of Physical Education and Sports, Beijing Normal University (IRB approval number: TY2023101002).

Table 1.

Basic information of the subjects (N = 177) (Mean ± SD)

Variables	Age (years)	Height (cm)	Weight (kg)	BMI (kg/m²)
/	20.85 ± 2.28	175.64 ± 6.16	65.22 ± 7.44	21.23 ± 1.99

Subjects

Male amateur marathon runners (N = 177) were enrolled from universities and running clubs in Beijing in October 2023. The inclusion criteria were age 18 to 30 years, running a minimum of ten kilometres per week, completing at least one marathon within one year and no history of injury within 3 months before the start of the study. subjects were excluded if they had a history of cardiovascular illness, previous reconstructive joint surgery or joint replacements. Baseline demographic data were collected during the baseline testing session.

Evaluation

Anthropometric

Baseline demographic, foot arch structure, training behaviour, injury history and dominant leg data were collected during a baseline testing session. Foot arch structure was measured via “footprint analysis” to conduct a simple self-assessment [24]. The participant took a standing posture with bare feet, dipped both feet in water before measurement, stepped on a blank paper in a naturally relaxed state, and formed a positive posture facing forwards with the centre of gravity in the centre of the body; the participant stayed for 3–4 s before leaving the paper, and footprints were obtained. If the water mark of the front foot and the back foot was disconnected, it was considered to indicate a high arch. If the arch impressions were connected but did not exceed the middle toe line of the foot, it was considered to indicate a normal arch. If the foot imprint was connected to the front and back of the foot and was almost the same width, it was considered to indicate a flat foo [24]. The dominant leg was determined by using coeffificients of asymmetry (the mean of the relative differences between the right and left side divided by 0.5, multiplied by the sum of right and left side [25].

Muscle strength test

The isometric strength of muscles was evaluated with MicroFet3 hand-held dynamometer (Hoggan Health Industries, West Jordan, Utah). Previous studies have reported that the reliability for muscle testing in the lower extremity, and reliability coefficients generally ranging from 0.95 to 0.99 [26, 27]. The strength of hip flexion, abduction, internal and external rotation, knee flexion and extension, ankle plantarflexion and dorsiflexion in subjects were tested in a random order. The order is chosen by the subjects themselves (according to their preferences). In addition, in order to ensure consistency in the placement of the dynamometer, all tests were performed by only one person (Daxin Li) who had received professional training on the equipment prior to testing. During the test, the tester held the dynamometer in a fixed position against which the participant performed maximum isometric muscle contractions.

To perform a standardized test, all subjects crossed their arms over their chest during the test. (1) Hip strength. To test the hip internal and external rotation strength, the subjects sat on the edge of a table, kept their upper body upright and crossed their hands in front of chest, the tester placed the dynamometer nearly 2 cm from the lateral and medial malleolus, respectively, the subjects were asked to perform internal rotation and external rotation against the dynamometer and maximum isometric strength was recorded. To test hip extension strength, the subjects were asked to lie prone on a yoga mat, with their hands behind their backs, the tester placed the dynamometer on the the lateral aspect of the distal thigh, nearly 2 cm from the lateral epicondyle of the knee, the subjects were asked to bend their knees 90°against the dynamometer and maximum isometric strength was recorded. To test hip abduction strength, the subjects were asked to lie on their side on a yoga mat, with their legs straight and closed together, the tester placed the dynamometer on the outer side of the distal thigh, 2 cm away from the lateral epicondyle of the knee, the subjects were instructed to lift their legs against the dynamometer [28]. (2) Knee strength. Knee extensor strength was tested with the subjects sat on the edge of a table, keep their upper body upright, cross their hands in front of their chest, bend their hip and knee joints at 90°. The tester placed dynamometer on the anterior aspect of the shank, proximal to the ankle joint, the subjects were instructed to lift their legs forward against the dynamometer. Knee flexion strength with the participant lying prone and hips and knees extended, and their hands behind their backs, the tester placed the dynamometer on the posterior aspect of the shank, proximal to the ankle joint, the subjects were instructed to lift their legs upward against the dynamometer [28]. (3) Ankle strength. Ankle plantar flexors strength was tested with the participant lying supine with the ankle in plantargrade and hips and knees extended, crossed their hands in front of their chest, the tester placed the dynamometer over the metatarsal heads on the sole of the foot, the subjects were instructed to kick the dynamometer and maximum isometric strength was recorded. Ankle dorsiflexors strength was tested with the participant lying supine with the ankle relaxed and hips and knees extended, crossed their hands in front of their chest, the tester placed the dynamometer over the metatarsal heads on the dorsum of the foot, the subjects were instructed to flex their feet back against the dynamometer and maximum isometric strength was recorded [28]. The recorded maximum isometric muscle strength, in newtons, were normalized to body weight (absolute values/ body weight) and accurate to 1%. Each action test was repeated for a total of 3 times with a 15-second rest, and the maximum value of the three tests was analyzed [29]. Calculate the value (dominant side- non-dominant side) as inter-limb asymmetry [30].

Registration of injuries

At the beginning of each month after the baseline demographic test, the training (training mileage, executing regular resistance training and running schedule or not) and injury statuses (the position and side of injury, the time of injuries occurrence and the duration of injury continue) of the subjects in the previous month were recorded. The type of injury included in this study is PF. The diagnostic criteria for PF [31, 32] were as follows: ① plantar medial heel pain that is most noticeable with initial steps after a period of inactivity but also worsens following prolonged weightbearing; ② positive windlass test; and ③ heel pain preventing the runner from executing the original plan for training and requiring a decrease in training speed or distance of more than one week or three consecutive planned running sessions [31]. All injuries included in the analysis were confirmed by experts and professors studying sport injuries. Injuries and sprains caused by engaging in other activities are excluded. If the subject experienced PF more than one time during the monitoring period, this study only included the first injury to avoid potential interference effects from previous injuries [33].

Statistical analysis

The Kolmogorov‒Smirnov test and Levene test were used to test the normality and homogeneity of variance of the continuous data, respectively. The data that does not conform to a normal distribution (the interlimb asymmetries of isometric strength of hip extension, hip abduction and knee extension) was converted using JMP 17.0. The independent-sample t test was used to compare the age, height, weight, BMI, running mileage and all testing indicators of injured and uninjured runners. Descriptive data were presented as mean and standard deviation. Binary logistic regression analysis was used to test the correlation between indicators and the dependent variable (PF), and indicators that may be correlated with PF were selected as the main factors (P < 0.1) for inclusion. Moreover, indicators that were significant (P < 0.05) according to independent-sample t test were also included as the main factors. In addition, multicollinearity between variables was tested via the variance inflation factor (VIF), and a VIF greater than 10 was considered to indicate severe multicollinearity between variables. The main factors screened through regression analysis and the independent-sample t test, as well as confounding factors selected in the multicollinearity test, were included in the final logistic regression analysis through stepwise regression analysis. We adjusted for the selected confounding factors, and the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Finally, ROC curves were generated to evaluate the diagnostic value of the significant predictors.

Results

A total of 177 male amateur marathon runners were included in this study. During the follow-up period, 2 runners suffered accidental injuries (ankle sprains), 3 runners did not complete follow-up and withdrew from the study. Among 172 subjects who completed a 3-month follow-up observation, 12 runners developed PF. The basic information of the injured and uninjured runners is shown in Table 2. No significant differences were observed between the two groups in terms of age, height, weight, BMI (P > 0.05) and significant differences were observed in monthly running mileage (P<0.05).

Table 2.

Basic information of runners with and without PF(Mean ± SD)

	Injured (n = 12)	Uninjured (n = 160)	P
Age (years)	20.50 ± 1.62	21.08 ± 2.86	0.489
Height (cm)	175.00 ± 6.15	175.61 ± 6.30	0.748
Weight (kg)	63.38 ± 5.50	65.43 ± 7.50	0.353
BMI (kg/m²)	20.68 ± 1.31	21.21 ± 2.07	0.391
Monthly Running mileage (KM)	76.43 ± 29.18	108.73 ± 53.04	0.039 #

Note: ^# means P<0.05; BMI: body mass index

The results of the interlimb asymmetries of lower limb isometric strength between the two groups are shown in Table 3. The results revealed that the interlimb asymmetries of hip abduction strength (P = 0.010) and knee flexion strength (P = 0.006) in injured runners were significantly greater than that of uninjured runners.

Table 3.

The interlimb asymmetries of strength in runners with and without PF (N/kg) (Mean ± SD)

Indicators	Uninjured (n = 160)	Injured (n = 12)	P	Effect size (95%CI)
Hip internal rotation	0.02 ± 0.50	0.10 ± 0.52	0.613	0.16(−0.37, 0.22)
Hip external rotation	0.07 ± 0.48	−0.01 ± 0.28	0.580	0.20(−0.20, 0.36)
Hip extension	0.08 ± 0.72	0.41 ± 0.54	0.122	0.52(−0.75,0.09)
Hip abduction	0.03 ± 0.55	0.46 ± 0.58	0.010 ##	0.76(−0.75,−0.11)
Knee extension	0.25 ± 0.90	0.25 ± 0.47	0.996	0.00(0.11, 0.60)
Knee flexion	0.10 ± 0.67	−0.26 ± 0.36	0.006 ##	0.67(−0.03,0.74)
Ankle plantarflexion	0.03 ± 1.51	0.15 ± 0.89	0.789	0.10(−0.99,0.75)
Ankle dorsiflexion	0.01 ± 0.59	0.05 ± 0.42	0.819	0.08(−0.38,0.30)

Note: ^# means P<0.05; ^##means P<0.01

Multiple collinearity diagnosis was performed on the control variables (height, weight, BMI, regular strength training or not, occur other running-related injuries or not, executing running schedule or not and foot arch structure) and main independent variables screened in this study (interlimb asymmetries of hip abduction isometric strength and knee flexion isometric strength), According to Table 4, VIF of the control variables (height, weight, BMI) was greater than 10, indicating the significance of multicollinearity. For other variables included in the study, there was no multicollinearity, which can ensure the stability of the results.

Table 4.

The results of multicollinearity test

Variables	VIF
Hip abduction strength	1.139
Knee flexion strength	1.138
Regular strength training or not	1.290
Occur other running-related injuries or not	1.164
Executing running schedule or not	1.214
Foot arch structure	1.048
Height	116.699
Weight	300.058
BMI	218.085

Significant predictors screened via binary logistic regression analysis and indicators with significance according to the independent-sample t test were analyzed as well as confounding factors (height, weight, BMI) were adjusted using stepwise regression analysis. The results of logistic regression analysis indicated that the logistic model was statistically significant (X² = 14.365, P = 0.001). Among the risk factors included in the model, the difference in the interlimb asymmetry of hip abduction isometric strength was significantly correlated with the risk of developing PF (OR = 3.646; 95% CI: 1.193–11.148; P = 0.023) (Table 5).

Table 5.

Logistic regression analyses for risk factors of PF

Risk factors	OR (95% CI)	P
Interlimb asymmetry of hip abduction strength	3.646 (1.193, 11.148)	0.023 #
Interlimb asymmetry of knee flexion strength	0.987 (0.440, 2.215)	0.975
Regular strength training or not	1.676(0.360, 7.797)	0.510
Occur other running-related injuries or not	1.175(0.302, 4.575)	0.816
Executing running schedule or not	1.523 (0.337, 6.992)	0.990
Foot arch structure	0.681 (0.104, 4.45)	0.688
Height	0.891 (0.266, 2.984)	0.851
Weight	1.13 (0.217, 5.892)	0.884
BMI	0.309 (0.004, 102.717)	0.869

Note: ^# means P<0.05

ROC curve analysis was used to calculate all possible thresholds and determine the optimal operating point for detection. The ROC curve, also known as the receiver operating characteristic curve, is a method to evaluate the merits of diagnostic tests and determine the critical value and is widely used in clinical medicine, epidemiology and other fields [34]. ROC curve analysis takes sensitivity as the vertical coordinate and (1-specificity) as the horizontal coordinate, which is a comprehensive index reflecting the continuous variables of sensitivity and specificity [35]. The ROC curve revealed that the sensitivity and specificity of the interlimb asymmetry of the hip abduction isometric strength for diagnosing PF with cut-off values of 0.325 were 0.667 and 0.238, indicating good discrimination. Morever, the area under the ROC curve was 0.717 (95%CI: 0.544–0.889, P = 0.012) (Fig. 1). According to the medical statistical diagnostic criteria, the diagnostic value is low when the area under the ROC curve is between 0.5 and 0.7, the diagnostic value is moderate when it is between 0.7 and 0.9, and the diagnostic value is good when it is above 0.9 [36].

Fig. 1.

Prediction of ROC curve for PF using interlimb asymmetry of hip abduction isometric strength. (The sensitivity and specificity of the interlimb asymmetry of the hip abduction isometric strength for diagnosing PF with cut-off values of 0.325 were 0.667 and 0.238, and the area under the ROC curve was 0.717, 95%CI: 0.544–0.889)

Discussion

Muscle strength refers to the ability to resist external resistance and is the most important determinant of the efficient movement and control of the body [37]. Muscle strength balance is crucial for muscle recruitment, accurate joint movement, and reduction of sports injuries, while strength imbalance will affect athletes’ muscle length-tension, muscle recruitment ability, motor control and neuromuscular performance [16]. This study is the first study to explored the relationship between the inter-limb asymmetries of muscle strength and PF in male amateur marathon runners and confirmed that the interlimb asymmetry of hip abduction isometric strength is a significant predictor of PF in male amateur marathon runners. Logistic regression analysis showed that the interlimb asymmetry of hip abduction isometric strength was significantly correlated with PF (OR = 3.646; 95%CI:1.193–11.148; P = 0.023). Previous study performed a prospective cohort study in novice conscripts to explore predictors of PF development after 10-week military training, the results indicated that the conscripts with poorer quality of movement and lesser femoral anteversion angle tended to exhibit PF. In addition, the conscripts with a higher level of physical exercise before military training had a reduced risk of presenting with PF [38]. At present, there are few prospective cohort studies on predicting the development of PF. This study is the first to conduct a prospective cohort study on PF in runners, and found that the interlimb asymmetry of hip abduction isometric strength is a significant factor in predicting the development of PF in male amateur marathon runners.

Previous studies have shown that runners with imbalanced hip abduction strength have a higher risk of lower limb injury [39]. By comparing the hip abduction strength of injured runners and uninjured runners, the study found that hip abduction strength of injured runners on the non-dominant side was significantly lower than that on the dominant side, with a difference of 13.5%. It has been demonstrated that weak hip abduction strength will cause the contralateral pelvis to drop, resulting in increased adduction torque of the knee, which in turn increases the ground reaction force upon touching the ground [40]. Abnormal gait can cause limbs to deviate from normal movement patterns [41], such as higher ground reaction forces, especially vertical oscillation, have been shown to be significantly correlated with the occurrence of PF [10]. In addition, previous studies showed that the interlimb asymmetries of strength more than 10% was considered to have asymmetric problems, and the difference of more than 15% will significantly increase the risk of injury [42, 43], which further confirms that the interlimb asymmetry of hip abduction isometric strength found in this study are important risk factors for PF in male amateur marathon runners.

It has been demonstrated that during the performance of bilateral movements, one side of the limb is activated more in overcoming load, in comparison with the other side of the limb—mostly targeting stabilization demands. Furthermore, during bilateral movements, a so-called bilateral deficit (i.e., the difference in the summed force between contracting muscles alone and contracting contralateral homologous muscles in combination) occurs [25]. If the runners have imbalanced muscle strength, their center of gravity will shift during the long running process. The dominant side bears more stress, which will not only increase the strength difference between the two limbs, but also increase the risk of overuse injury of the dominant side, which can further explain why the PF in our study mainly focused on the dominant side (10 cases). In addition, if the training load is too high or recovery is not sufficiently effective, symptoms of fatigue develop quickly. A prolonged imbalance in this relationship leads to functional overreaching and can worsen performance further, which may increase the risk of injury [44]. Therefore, for clinicians, it is suggested to pay attention to the balanced development of bilateral muscle strength in the process of PF rehabilitation treatment, and regard the improvement of the interlimb asymmetry of hip abduction isometric strength as one of the rehabilitation therapies. Morever, for runners and coaches, it is suggested that they should appropriately add unilateral or bilateral strength training (such as side-lying hip abduction training, clamshell exercise, supine bridge, etc.) [45] in the daily training to ensure the balanced development of hip abduction strength, so as to prevent the occurrence of PF.

Although this is the first study to explore a significant relationship between the difference in hip abduction isometric strength and PF, some limitations in this study should be taken into consideration. First, in this prospective study, only twelve runners experienced PF within the three-month observational period, which may affect the robustness of the results and lead to reduced sensitivity and specificity of the diagnosis. An important question for future studies is to investigate a larger sample and follow up a longer period, which can provide stronger evidence for coaches to design specific training programs. Second, only male runners were included; as a result, the findings should only apply to male amateur marathon runners. In the future, prospective studies will be conducted among female runners to establish sex-specific PF prevention model. Third, this prospective study explored the relationship between the interlimb asymmetry of lower limb isometric strength and PF; however, biomechanical factors may also be another key factor leading to PF. Further study will be conducted to screen for biomechanical risk factors closely related to PF in the future.

Conclusions

Based on the current findings, the interlimb asymmetry of hip abduction isometric strength was associated with a greater likelihood of developing plantar fasciitis, and interlimb asymmetry of hip abduction isometric strength greater than 32.5% was a significant risk factor for the development of plantar fasciitis in male amateur marathon runners. The risk of PF occurence increased by 3.646 times if the interlimb asymmetry of hip abduction isometric strength greater than 32.5%. For clinicians, it is suggested to pay attention to the balanced development of bilateral muscle strength in the process of PF rehabilitation treatment, and regard the improvement of the interlimb asymmetry of hip abduction isometric strength as one of the rehabilitation therapies. Morever, for runners and coaches, it is suggested that they should appropriately add unilateral or bilateral strength training (such as side-lying hip abduction training, clamshell exercise, supine bridge, etc.) in the daily training to ensure the balanced development of hip abduction strength, so as to prevent the occurrence of PF. In the future, prospective studies will be conducted among female runners to establish sex-specific PF prevention model and biomechanical risk factors closely related to PF should be explored in the future.

Author contributions

Li Daxin: Investigation, Formal analysis, Writing-Original Draft; Liu Yangli: Investigation, Writing-Review & Editing; Feng Yangya: Investigation, Writing-Review & Editing; Peng Cheng: Investigation, Writing-Review & Editing; Tang Donghui: Writing-Review & Editing, Supervision; All authors approved the final version of the manuscript.

Funding

This study was supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 71874017).

Data availability

To protect the privacy of participants, the data will not be disclosed to the public. If necessary, you can contact the corresponding author.

Declarations

Ethics approval and consent to participate

In accordance with the Declaration of Helsinki, this study received Institutional Ethics Approval from the College of P.E and Sport, Beijing Normal University, China (IRB approval number: TY2023101002). Informed consent was obtained from all subjects involved in the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Clinical trial number

Not applicable.