Effects of resistance training on gait and muscle strength improvement in unilateral transfemoral amputees: a pilot investigation

Abstract

The aim of this study was to evaluate the effectiveness of a commonly used resistance training program in mainland China—characterized by high frequency and short duration—for unilateral transfemoral amputees. We assessed participants before and after the intervention using the Six-Minute Walk Test (6MWT), isokinetic muscle strength testing, and gait parameter analysis. The exercise intervention targeted hip muscle groups (adductors, abductors, and extensors) and consisted of four sets of 15 repetitions, with a 1-minute rest between sets and a 15-minute rest before switching muscle groups to minimize fatigue. Participants completed 6 consecutive days of training, followed by assessments after 1 day of rest. A total of 15 patients from the Prosthetics and Orthotics Department (P&OD) with unilateral transfemoral amputation were initially screened for eligibility. 12 of them were recruited; one was excluded for personal reasons, resulting in a final sample of 11. All participants had used their prosthesis for more than 1 year prior to the study. Post-training, significant improvements were observed in hip abductor and extensor strength on the amputated side at angular velocities of 60°/s and 180°/s. Walking distance increased significantly (p = 0.006), and hip abduction angle during the swing phase also increased significantly. This pilot study demonstrates that high-frequency resistance training can substantially improve specific aspects of muscle strength and walking ability in a short period for unilateral transfemoral amputees. These findings provide preliminary evidence to inform rehabilitation strategies for transfemoral amputees in resource-limited settings.

Chinese clinical trial registry: Registration number：ChiCTR2500103608, Date of Registration：03-06-2025, https://www.chictr.org.cn/showprojEN.html?proj=268907

Chapter 1. Introduction

Background

Lower limb amputation and transfemoral amputation

Transfemoral amputation (TFA) is a major subtype of lower limb amputation (LLA). Surgical alterations to musculature often result in imbalances among hip muscle groups, leading to reduced hip abductor function during the stance phase and poor adductor control during the swing phase¹. These anatomical changes frequently lead to residual limb deformities and measurable gait deviations, including reduced step frequency, larger step width, and increased stride length^2–4. Current rehabilitation guidelines prioritize active engagement of the hip extensors over reliance on the prosthesis for knee stabilization, as muscle weakness directly impairs prosthetic control in complex environments⁵. Targeted hip strengthening is therefore critical for optimizing gait coordination and energy efficiency.

Resistance training

Rehabilitation training is an important part of the rehabilitation process among amputees, the benefits of resistance training in amputees, as well as in non-amputees, seem to outweigh the risks. Due to their objective condition, amputees always face challenges in performing activities of daily living, and resistance training can help improve functional performance in these activities. Exercise has many positive effects on them that’s why the lack of sufficient exercise and the limited use of prostheses are among the major causes of muscular weakness⁶.

Resistance training need body’s muscles working against an opposing force, is also one of the most common methods in clinical training. It requires physiotherapists to plan a suitable content which include sequence, rest time between each set, the number of repetitions and the intensity for exercises to achieve optimal results⁷.

Literature review

There is a great amount of studies that have looked into the issue of resistance training as a means to improve functional outcomes in those with LLA⁸. While they agree on the area of concern, further details on duration, frequency, and content are varied across these studies. Where the duration of training was noted, it ranged from 3 weeks to up to 20 weeks⁶, while the frequency was usually between 1 and 3 per week⁹. Resistance training has been identified with improved muscle strength, balance, and gait efficiency that is very relevant for enhancing prosthetic function and daily mobility¹⁰.

However, the situation in mainland China differs from the ideal conditions presented in the studies. Only a small number of patients have access to long-term rehabilitation in professional institutions, and economic and institutional factors further limit the duration and scope of rehabilitation protocols. Therefore, it is essential to adapt and improve strategies to better address these specific conditions and help individuals with amputations achieve optimal training outcomes¹¹. Currently, research on the design of resistance training programs for amputees in mainland China remains limited.

Through visits to various rehabilitation institutions in mainland China that provide services for individuals with above-knee amputations, a commonly used training model involves 1 week of intensive training, with 6 sessions per week, aimed at achieving rapid functional gains. However, the effectiveness of this approach still requires experimental validation.

Objectives

The primary objective of this study is to determine whether a commonly used resistance training regimen can significantly improve hip muscle strength in individuals with unilateral transfemoral amputation. It is hypothesized that participants will show greater gains in hip muscle strength following the intervention compared to baseline. Secondary objectives include evaluating the effects of the regimen on functional outcomes such as gait and balance, with the expectation that improvements in muscle strength will be associated with enhanced functional performance. The results aim to inform the optimization of rehabilitation strategies and provide clinical reference for similar patient populations.

Chapter 2. Design and methodology

Subjects

Transfemoral amputees from Prosthetics and Orthotics Department (P&OD) were recruited in this study. All study procedures were conducted between December 2023 and December 2024, with approval from the CRRC Ethics Committee and in accordance with ethical standards for human research. All methods were performed in accordance with the relevant guidelines. All procedures were thoroughly explained to participants prior to the study. Each participant was fully informed about the study content, duration, and compensation, and provided written informed consent.

A priori sample size estimation was conducted using G*power software (Version 3.1.9.6). A recommended sample size of 10 participants was estimated, assuming a fixed effect size of 0.8⁶ (large), a power of 0.95, and an alpha of 0.05.

A total of 15 patients were initially screened for eligibility. Of these, two did not meet the inclusion criteria and one declined to participate. 12 participants were subsequently enrolled in the study. Before the intervention began, 1 participant withdrew for personal reasons. Ultimately, 11 participants completed the intervention and post-intervention assessments, and their data were included in the final analysis. The basic information of subjects has showed in Table 1.

Table 1.

Basic information of subjects.

	Amputated side	Sex	Age	Weight [kg]	Height [m]
1	L	Female	19	82	1.68
2	L	Male	51	75	1.72
3	R	Female	28	60	1.6
4	R	Male	53	77.5	1.7
5	R	Female	31	56	1.6
6	R	Male	45	72	1.75
7	R	Male	64	75	1.7
8	L	Male	36	80	1.74
9	L	Male	23	90	1.7
10	R	Male	29	90	1.8
11	R	Male	57	85	1.76
Mean			39.64	76.59	1.70
Std. Deviation			14.37	10.43	0.06

L: Left R: Right

A flow diagram of participant recruitment, exclusion, and retention is presented in Fig. 1.

Fig. 1.

Participant recruitment flow.

Inclusion criteria

Participants were unilateral transfemoral amputees aged 18 to 65 years, with amputation resulting trauma, tumor or other causes. All had clear consciousness, no cardiovascular or cerebrovascular disease, and were able to cooperate with testing. Each participant had been fitted with a prosthesis and had used it for more than one year, with stable residual limb conditions and proficiency in daily prosthesis use. All subjects were recruited from the P&OD, where prosthesis quality was generally consistent. Before the study, each participant’s prosthesis was checked and adjusted by their prosthetist to ensure good fitting.

Exclusion criteria

Exclusion criteria included spinal cord injury or hemiplegia, multiple limb amputations, lack of control of own prosthesis, and any medical or psychological condition that could interfere with participation.

These criteria ensured that participants’ conditions were suitable for obtaining valid and reliable results.

Exercise intervention

The resistance training program lasted for one week and was supervised throughout by the same experienced physiotherapist, who has specialized in amputee rehabilitation for over 20 years, to ensure consistency and safety.

Participants completed the exercise protocol over six consecutive days, followed by assessments after one day of rest. The exercises targeted the hip adductors, abductors, and extensors, aiming to improve hip stability and function for better gait and prosthesis use.

① Adductors (Fig. 2): In the supine position, resistance is provided by an elastic band. One end of the band is fixed to the terminal portion of the residual limb, while the other end is attached to a stable anchor point. The participant performs hip adduction in the horizontal plane and ensure proper engagement of the adductor muscles.

Fig. 2.

Resistance training of adductors.

② Abductors (Fig. 3): The subject lies laterally with the residual limb on top, ensuring the body remains in a straight alignment. The unaffected leg is slightly flexed to enhance stability during the movement. A 2 kg sandbag is placed outside the terminal end of the residual limb to provide resistance during the hip abduction.

Fig. 3.

Resistance training of abductors.

③ Extensors (Fig. 4): In the prone position, the exercise involves placing a 2 kg sandbag on the posterior side of the residual limb’s distal end. The subject then performs posterior extension movements while maintaining an adducted posture of the hip.

Fig. 4.

Resistance training of extensors.

If the subject has developed a hip flexion contracture, it may be necessary to reposition posture to allow the movement to be performed.

Each exercise was performed for 4 sets of 15 repetitions, with a 1-minute rest between sets and a 15-minute rest before switching to the next muscle group to avoid fatigue. All movements were performed at a steady pace, and the protocol was kept consistent for all participants.

At the first training session, resistance (elastic band tension or sandbag weight) was individually adjusted according to each participant’s ability to ensure moderate exertion (Borg scale 12–14). The selected resistance was then kept constant for the remainder of the training period. No participants reported excessive fatigue or adverse effects.

Participants were asked to maintain their usual daily routines and not to engage in additional exercise during the study.

Procedure

Basic information entry and Pre- assessment on functional and physical capabilities was conducted before training. Assessments included isokinetic muscle strength tests of the hip muscles (adductor, abductor and extensor); functional mobility was assessed with the 6MWT; detailed gait parameters, were further monitored with the aid of Inertial Measurement Units (IMUs). All subjects then underwent the same series of post-training examinations after exercise intervention.

Isokinetic muscle strength test

Muscle strength is defined as the maximum force (N) or torque (Nm) generated during maximal voluntary contraction. Dynamic endurance refers to a muscle’s ability to repeatedly contract and relax over time, typically measured by the number of repetitions completed within a specified duration¹². Isokinetic Dynamometer which showed in Fig. 5 serves as the gold standard for quantifying neuromuscular performance, providing precise measurements. Its velocity-controlled mechanism ensures replicable dynamic assessments critical for tracking rehabilitation progress^13,14.

Fig. 5.

Isokinetic dynamometer.

In this study, muscle strength was assessed using the Isokinetic Dynamometer as the average peak torque from five repetitions at an angular velocity of 60°/s. Muscle endurance was evaluated as the mean of peak torque across all repetitions performed at 180°/s. Isokinetic testing was chosen for its ability to provide controlled and standardized measurements, which is particularly important for individuals with transfemoral amputation. Although recent studies have shown that repetition maximum (RM) prediction methods can also be effective for strength assessment¹⁵, direct RM testing may not be suitable for this population due to safety and consistency concerns. Future research may consider combining isokinetic testing with RM prediction approaches to further improve measurement accuracy.

Before each test, all participants completed a standardized warm-up protocol including 5 min of walking with their prosthesis at a comfortable pace, following by dynamic stretching of the hip and residual limb. Familiarization was ensured by allowing participants to perform several practice trials on the device until they felt comfortable with the positioning and movement. During testing, participants wore their prosthesis and were positioned on the dynamometer according to established protocols: the technician carefully aligned the participant’s hip joint axis with the device’s rotation axis and performed LIDO’s standard gravity calibration procedure¹⁶. Consistent positioning and strapping were maintained throughout all tests to ensure reliability, following recommendations for measurement standardization and reliability assessment¹⁷.

During each test, verbal encouragement was provided to motivate participants to exert maximal effort in both speed and force until instructed to stop¹⁸.

Hip strength was measured on both limbs, starting with the intact limb followed by the amputated side.

Gait parameter collection

Noraxon Inertial Measurement Units (Fig. 6), coupled with myoMOTION analytics software¹⁹ were used for this test and following Noraxon’s guidelines to collect optimal data. Before the experiment, a licensed prosthetist verified and readjusted the fit, alignment, and force distribution of the prostheses for all participants to address potential issues related to improper prosthetic use²⁰.

Fig. 6.

Noraxon inertial measurement units.

Sensors were placed on specific anatomical locations which show in figure. As the study focused on trunk and lower limb dynamics, sensors were not applied to the head and hands (Fig. 7).

Fig. 7.

Sensor distribution.

After neutral position and walking calibration, we analyzed the average values from multiple gait cycles during a single walk. The main measured parameters were the hip abduction angle during both the stance and swing phases, the stance phase of amputation side, and the average velocity²¹.

Six-minute walk test

6MWT (Fig. 8) simple yet comprehensive test measures the distance a patient can walk on flat ground during six minutes, thereby offering a practical, real-life assessment of the functional exercise capacity²². The experiments adhered strictly to procedural guidelines. Pre- and post-training assessments were conducted by the same evaluator under identical environmental conditions and at the same time of day to ensure consistency²³.

Fig. 8.

Six-minute walk test²³.

Following the test, the Borg dyspnea and fatigue levels were recorded, along with the number of laps completed. The total distance walked was calculated in meters.

Statistical analysis

Statistical analyses were conducted using IBM SPSS Statistics software (version 29). The descriptive statistics are presented with mean and standard deviation.

The normality of the sample was explored and analyzed using Shapiro-Wilk tests. All explored variables were fulfilled normal distribution (p > 0.05). After confirmation of normality the Paired t-Test was used to compare and analyze whether the differences between pre- and post-training data on muscle strength, gait parameters, and walking ability tests were significant. The Cohen d test was executed to analyze the pairwise effect size.

Chapter 3. Results

All 11 participants completed the full experimental procedure, and data were successfully obtained for analysis.

Muscle strength

Comparative analysis of average peak torque values revealed distinct muscle responses to angular velocities.

The following Table 2 presents the statistical results of peak torque at each muscle group both pre- and post-training. For all muscle groups except the adductors, negative t-values indicated that post-training values were greater than pre-training values. Additionally, for all muscle groups except the adductors, two-tailed p-values were less than 0.05, indicating significant changes.

Table 2.

The peak torque statistic result of Abductors, extensors and Adductors.

Muscle	Correlation test	Mean	Std	t	p (two tailed)	95% CI	Cohen’s d
Abductor (60°/s)	0.90	-8.70	9.55	-3.02	0.01	(-15.12, -2.28)	-0.91
Extensor (60°/s)	0.86	-9.68	12.49	-2.57	0.03	(-18.08, -1.28)	-0.78
Extensor (180°/s)	0.39	-11.24	17.06	-2.28	0.04	(-22.72, 0.24)	-0.66
Adductor (60°/s)	0.64	2.74	19.85	0.46	0.66	(-10.58, 16.06)	0.14

Peak torque of abductor and extensor(60/180degree per second) incressed significantly after training with p=0.01/0.03/0.04.

Gait parameters

We examined the changes in key gait parameters pre- and post-training, focusing on the following aspects: the hip abduction angle during both the support and swing phases, the step length discrepancy between the amputated and sound limbs, the proportion of stance phase duration on the amputated side, and the average walking speed.

Table 3 shows a decreasing trend in mean post-training abduction angle during the mid-stance phase and an increasing trend during the swing phase. The hip abduction angle during the swing phase indicating a statistically significant increase (p = 0.009). On the amputated side, both the duration of the stance phase and mean of average velocity increased. However, the change was not statistically significant.

Table 3.

Statistic result of gait parameters.

Gait parameters	Correlation test	Mean	Std	t	p (two tailed)	95% CI	Cohen’s d
Hip abduction angle (mid stance)	0.88	0.77	1.82	1.40	0.19	(-0.46, 2.00)	0.42
Hip abduction angle (swing phase)	0.87	-2.65	2.88	-3.19	0.01	(-4.59, -0.71)	-0.92
Stance phase (amputation side)	0.12	-2.23	7.83	-0.94	0.37	(-7.49, 3.03)	-0.28
Average velocity	0.83	-0.31	0.61	-1.67	0.13	(-0.71, 0.09)	-0.51

Hip abduction angle during swing phase incressed significantly after training with p=0.01.

Walking distance in 6MWT

According to Lin and Bose²⁴, the 6MWT walking distance is a practical measure of an individual’s ability to ambulate within a community setting. In this study, 10 out of 11 participants demonstrated an increase in their walking distance post-training.

The paired t-test for walking distance showed that the mean post-training value was significantly higher than the pre-training value (t = -3.45, p = 0.006). The result showed in Table 4.

Table 4.

Statistical results of distance.

	Correlation test	Mean	Std	t	p (two tailed)	95% CI	Cohen’s d
6MWT Distance	0.97	-22.46	21.26	-3.50	0.01	(-36.74, -8.17)	1.05

Walking distance of 6MWT incressed significantly after training with p=0.01.

Chapter 4. Discussion, conclusions and perspectives

Discussion

Our protocol was designed as a short-term intervention; therefore, the analysis primarily focuses on the immediate effects of training. Whether these improvements can be maintained or further enhanced over the long term remains to be determined in future studies.

Muscle strength

The gluteal muscles are fundamental in helping amputees maintain balance, stability, and effective prosthetic control²⁵. As such, their rehabilitation deserves particular attention. In addition to refining surgical techniques to optimize muscle fixation, rehabilitation should focus on targeted strengthening of weak muscle groups. Recent randomized controlled trials, such as the study by Agrebi et al.²⁶, have shown that specific resistance training can significantly improve isokinetic muscle strength and correct muscle imbalances. These findings highlight the value of evidence-based resistance training in the rehabilitation of amputees.

Muscles with expected growth

Our results show that the strength of the hip extensors and abductors improved significantly as expected, with the extensors also demonstrating excellent performance in medium- and high-speed tests (Fig. 9). This may suggest that the endurance of the extensors also improved after training.

Fig. 9.

Role of extensor in initial contact.

These results align with findings from pilot studies in adolescent populations, where resistance training led to both physical improvements and enhanced self-perception of progress²⁷. Although our study focused on amputees, the positive perceptual and psychological outcomes reported in other groups highlight the potential for similar benefits in this population. Future research could explore how resistance training influences amputees’ self-efficacy, body awareness, and overall psychological well-being during rehabilitation.

Muscles with non-significant growth

No significant changes were observed in hip adductor strength. Several factors may explain this finding: range of motion limitations, such as contractures of the hip flexors or abductors, may prevent adequate activation of the adductors during exercise. Additionally, imbalances in muscle distribution, with external muscles such as the abductors being better preserved during surgery, may lead to dominance during exercise and reduced adductor engagement. Addressing these challenges in rehabilitation requires strategies focused on reducing contractures, promoting proper adductor activation, and implementing progressive resistance training.

Individual variability

While significant improvements in muscle strength were observed in the abductor and extensor groups, a small number of participants showed no progress or even slight declines. These results may be attributable to individual differences in physical fitness. The experimental design maintained consistent exercise volumes across all participants to ensure uniform testing conditions. However, variations in age, gender, previous exercise history, and amputation level likely affected the outcomes achieved within this standardized approach. Therefore, it is critical to customize training plans based on individual needs.

Gait parameter

In this study, we used gait metrics of healthy individuals as a benchmark, allowing the outcomes of amputees to be evaluated against this standard. Following training, there were some changes in gait metrics for most participants²⁸. A pilot research has shown that training load can influence gait variability, which may explain why certain parameters change significantly while others do not under non-progressive training load training²⁹.

Hip adduction angle (Stance phase)

After training, the significant increase in the strength of the hip abductor and extensor muscle groups improved participants’ ability to control their prostheses. This enhanced control allowed them to confidently use prosthetic side during the single-support phase, facilitating a greater shift of their center of gravity (COG) toward the prosthetic limb. Gait parameters recorded using IMU sensors supported this hypothesis, showing a trend toward increased femoral adduction angles (reflecting a shift in the COG) during mid-stance on the amputation side for most participants, though these changes were not statistically significant. Ryser et al. demonstrating linear increases in abductor strength correlating with femoral angle adjustment. Gravitational compensation revealed 0.97% (0.29–1.5% range) peak torque enhancement per degree of angular change³⁰. That means even a one-degree increase in femoral adduction angle can enhance the strength and function of the hip abductors, thereby improving gait stability. Given the strong correlation between femoral adduction angle and hip abductor activation, we believe the resistance training program achieved promising outcomes in this aspect. Additionally, prosthetic alignment and design play a significant role in gait dynamics³¹. To maintain experimental consistency, no modifications were made during trial. Consequently, the rigid initial alignment may limit to observe changes in femoral adduction angle.

Hip abduction angle (Swing phase)

After training the mean of hip abduction angle in swing phase increased significantly. Comparative data from healthy individuals suggest a decreasing hip abduction angle during the swing phase, from approximately 10° to 7°³². Most subjects in our study continued to deviate from the normative pattern for healthy individuals, exhibiting increased abduction. Notably, among the 11 participants, 5 showed hip abduction angles during the swing phase that exceeded the average range typically reported for transfemoral amputees after the increase, indicating a more pronounced deviation from both healthy and amputee normative values. This deviation is likely due to an imbalance in the strength of the medial and lateral hip muscle groups. To correct the imbalance in hip muscle groups and enhance gait efficiency, recommended that targeted strengthening of hip adductors. Personalized rehabilitation programs of individual muscle strength imbalances and gait deviations may lead to more effective outcomes.

Wissem Dhahbi et al. emphasize the interconnectedness within the kinetic chain, meaning that movement in one joint influences the cranial and caudal adjacent joint patterns³³. However, our training program’s exclusive focus on a single hip joint may disrupt this kinetic chain. Concurrently, the brief duration of the experiment limited participants’ adaptation time, potentially contributing to aberrant performance.

Future training regimens should consider integrating the sound side, trunk and upper limb to optimize entire functional outcomes.

Symmetry of gait

For amputees, ambulation is often characterized by reduced standing duration on the prosthetic side, prolonged swing and step durations³⁴, and lower overall step frequency compared to healthy individuals¹. Upon analyzing the results, it was observed that while most participants demonstrated expected improvements—such as increased weight-bearing duration on the prosthetic side, extended stride length on the intact limb, and higher stride frequency—these changes were not statistically significant. Furthermore, some pre- and post-training results lacked strong correlation.

our findings indicate that resistance training can induce specific changes in gait parameters, but the overall impact on gait symmetry and efficiency may be limited by factors such as training load, duration, and individual variability. Incorporating the assessment of gait variability and adopting a multidisciplinary approach may enhance rehabilitation outcomes for amputees.

Walking ability (6MWT)

The findings from the 6MWT indicated that the subjects demonstrated significant improvements in walking distance, reflecting enhanced functional capacity, balance, postural control, and community ambulation ability²⁴. However, no substantial changes were observed in walking speed data obtained through IMU sensors. This suggests that resistance training primarily enhanced long-distance walking endurance without affecting walking speed. Participants were able to reduce the frequency and duration of breaks within the same six minutes, covering a greater distance at a similar pace.

Conclusion

This study explored the short-term effects of a one-week high-frequency resistance training program in individuals with unilateral transfemoral amputation. The intervention led to measurable improvements in hip muscle strength and walking ability. However, an increase in hip abduction angle during the swing phase was observed, deviating from normative gait patterns and potentially indicating an imbalance between medial and lateral hip muscle groups. The exclusive focus on the hip joint may also have disrupted the kinetic chain. These findings point to the value of individualized rehabilitation programs that address specific muscle imbalances, such as by strengthening the hip adductors and incorporating the sound side, trunk, and upper limb for more comprehensive functional gains.

Features, limitations and perspectives

The study’s limitations include a short intervention period, lack of progressive overload in the training protocol, small sample size, and absence of follow-up, which restrict the ability to draw conclusions about long-term effectiveness and generalizability. The brief duration of the training may not be sufficient to induce lasting physiological adaptations, and the observed improvements might not persist. Participants were not instructed to progressively increase the load during the resistance training program; instead, the same resistance was used throughout the intervention period. Compare with the study of Marinelli et al.³⁵ which designed progressive overload, this protocol may have limited their potential for improvement. Additionally, the limited sample size, although estimated a priori, may not fully capture the variability within the broader amputee population.

Future research should include larger cohorts, extended follow-up, and, where feasible, the incorporation of a control group to assess the durability of training effects and refine rehabilitation protocols, potentially through multicenter collaboration or larger sample recruitment.

Abbreviations

6MWT

Six-minute walk test

P&OD

Prosthetics and orthotics department

TFA

Transfemoral dmputation

LLA

Lower limb amputation

IMUs

Inertial measurement units

RM

Repetition maximum

COG

Center of gravity

Author contributions

Author 1 served as the principal investigator and, with the support of 2, defined the scope and content of the research. Author 3, 6 , and 9 contributed significantly to the development of a feasible operational protocol. Throughout the project, 7, 8, 10 ,11and 12 actively participated and provided valuable insights. Author 5, as the physical therapist, designed the training methods employed in the experiment and was responsible for instructing the participants. Author 4, as the rehabilitation assessor, designed the muscle strength assessment component of the study and conducted the preliminary analysis of the results.

Data availability

The principal investigator will oversee the intra-study data sharing process. All investigators at individual study sites will be given access to the cleaned data sets. Data sets will be housed on the Poly U Research Data Repositor. Investigators will have direct access to their own site’s data sets and will have access to other sites data by request. To ensure confidentiality, any data dispersed to investigators will be blinded of any identifying participant information.DOI https://doi.org/10.60933/PRDR/LHMXYWIf have any problems during obtaining the data, please feel free to contact the first author (23049127 g@connect.polyu.hk).

Declarations

Competing interests

The authors declare no competing interests.