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Abstract:Sports biomechanics mainly investigates the mechanical laws governing human movement and equipment in sports, and is an important supporting discipline in the scientific research of competitive sports. This review summarizes recent advancements in data collection and computational analysis techniques in sports biomechanics. On this basis, it focuses on the research progress made in 2024 regarding the application of biomechanics in enhancing sports performance, preventing and rehabilitating sports injuries, and developing sports equipment. The aim is to provide a reference for researchers in China, broaden research perspectives, and promote the in-depth application and development of this discipline in the field of competitive sports.

Abstract:The increasingly widespread application of artificial intelligence (AI) technology in the field of sports biomechanics has provided more effective technological support for competitive sports science to help athletes improve their performance. Using AI technologies and methods to obtain athletes’ biomechanical data, analyze the biomechanical characteristics of movement techniques, design training plans, adjust tactical strategies, and prevent sports injuries has become an integral part of high-level competitive sports. This paper summarizes the current applications of AI technology in sports biomechanics through a literature review, including its applications in movement technique analysis for performance enhancement, tactical analysis, and sports injury prevention. The goal is to provide new ideas for further promoting the application of AI technology in sports biomechanics, offer new methods and means for competitive sports science and technology, and create more possibilities for the development of AI technology itself.

Abstract:Objective The combined entropy weight technique for order preference by similarity to an ideal solution (TOPSIS) and rank sum ratio (RSR) method were utilized to rate the protective performance of ice hockey helmets, and the effectiveness and influencing factors of the rating system, as well as the relationship between protective performance and purchase price were explored. Methods The linear acceleration data during impact drops of twenty-four ice hockey helmets were collected using a uniaxial accelerometer in a collision test machine after low and ambient temperature treatments. The protective performance of ice hockey helmets was rated using the STAR model combined with the entropy weight TOPSIS and RSR methods. One-way ANOVA or the Kruskal-Wallis H test was employed to assess the differences in protective performance among helmets across different grade groups. The correlation between different indicators was analyzed by Pearson’s correlation coefficient. Results The comprehensive protective performance ratings of the CCM TACKS 310, IBX, BAUD, and WARRIORS COVERT RS PRO helmets were classified as poor, whereas the BAUER REAKT 150, HYPERLITE, and REAKT 200 helmets were rated as excellent. The remaining helmets were rated as moderate. There was a moderate to high positive correlation between the ambient temperature STAR(A) and Rowson’s STAR values, the comprehensive Ti and low temperature Ti, the comprehensive Ti and ambient temperature Ti (P<0.05). The comprehensive Ti satisfied the homogeneity of variance (P>0.05) and exhibited significant differences among groups (P<0.05). Significant differences were found in the low temperature indicators among different groups (P<0.05), and their weight coefficients ranked among the top three. The ambient temperature indicators were not affected by the protective performance grade (P>0.05). A weak positive correlation existed between the comprehensive Ti and purchase price (P<0.05). Conclusions According to the energy absorption test protocol, the combined entropy weight TOPSIS and RSR methods can efficiently rate the comprehensive protective performance of ice hockey helmets. The effectiveness of using low temperature indicators for the comprehensive evaluation and rating of ice hockey helmet protective performance is superior to that of ambient temperature indicators and purchase price. Consumers are advised not to use price as a criterion for evaluating the comprehensive protective performance of ice hockey helmets.

Abstract:Objective To improve the underwater technique during the start phase of breaststroke swimmers through swimming flume training and assess its effectiveness in enhancing competitive performance. Methods The participants were 14 male swimmers at the short-distance Level 4 category from the Shanghai Swimming Team, and they were randomly divided into the experimental group (n=7) and control group (n=7). The experimental group underwent swimming flume start training, while the control group underwent regular pool start training, and both groups received the training twice a week for 16 weeks. Before and after the 16-week training, a 15-m breaststroke start test was conducted. Repeated measures analysis of variance and paired t-tests were used to compare the changes in kinematic parameters (time, speed, and entry angle) between and within groups. Results After 16 weeks of specialized training, the 15-m performance at the start for the experimental group and control group (F(1,12)=6.52, P<0.05, η2= 0.39）showed an interaction, with the experimental group performing better after training compared to the control group before training (P<0.05). In the experimental group, the duration of the pull out phase (F(1,12)=10.28, P<0.01, η2=0.46) and the second sliding phase (F(1,12)=4.81, P<0.05, η2=0.22) was improved; the distance of the pull out phase (F(1,12)=4.71，P<0.05，η2=0.21) and the second sliding phase (F(1,12)=4.81, P<0.05, η2=0.22) was improved; the speed of the pull out phase (F(1,12)=4.77, P<0.05,η2=0.20) was significantl improved. The within-group statistics showed that the experimental group significantly improved their exit speed (P<0.05). The hand entry angle was optimized (P<0.05), while changes in other joint angles were not significant. Conclusions Swimming flume training reduced the time spent in the pull out and second gliding phases during the breaststroke start, effectively preventing the speed loss during underwater gliding. This provides an experimental evidence for enhancing start performance and optimizing training methods for breaststroke swimmers.

Abstract:Objective The athletic performance and physiological indicators of two top seated cross-country skiers during simulated competitions were analyzed, and the characteristics of exercise intensity and pacing strategies in different terrains were explored, so as to provide a scientific basis for physical fitness allocation and speed rhythm optimization of the athletes. Methods Differential global positioning system and Momentum Technology MT-Sports T2 were used to test athlete A and athlete B with class of locomotor winter 10 (LW 10), who were the first and second runners-up of Beijing Winter Paralympic mid-distance cross-country ski race. The athletes’ real-time gliding speed and heart rate during five consecutive 15-km cross-country skiing time trials were collected, and the time spent on each section, speed and heart rate changes in each course were analyzed. Results The coefficient of variation (CV) of mean heart rate on uphill and flat terrain sections were significantly correlated with total scores. The average gliding speed and average heart rate as a percentage of maximum heart rate (HRmax) of the athletes in three terrains were significantly correlated with total scores. The correlation between the mean time spent on uphill and flat terrain and total performance was stronger than that between the mean time spent on downhill terrain and total scores. Both athletes used a cumulative acceleration speed rhythm. Conclusions Uphill and flat terrain time are critical to race performance. Athletes adopt a progressive pacing strategy, gradually increasing speed in the first half, maintaining stable output in the mid-race, and finishing the last lap at a high-speed. Heart rates are mainly distributed between 70%–90% HRmax, and balancing high-intensity efforts on uphills with recovery on downhills helps optimize energy expenditure.

Abstract:Objective To analyzed the surface electromyography (sEMG) characteristics of high-level male speed climbers using Tomoa skip technique, and provide a theoretical basis for the determination of special strength training methods and means. Methods Ten male speed climbers at national first level or above were recruited, and their kinematics and sEMG signal data using Tomoa skip technique during climbing the official route were collected. Results For using Tomoa skip technique, the order of the main muscle contribution rate of high-level male speed climbers was biceps brachii, triceps brachii, flexor digitorum superficialis, latissimus dorsi, anterior tibial, vastus lateralis, gluteus maximus, medial head of gastrocnemius muscle. The sum of all muscles contribution rates of the left side, the contribution rate of biceps brachii and triceps brachii were significantly lower than that of the right side (P<0 05). The contribution rate of medial head of left gastrocnemius muscle was significantly higher than that of right side (P<0 05). The level of activation of the left biceps brachii was significantly lower than that of the right (P<0.05). The co-contraction indexes of left elbow joint and ankle joint, right elbow joint and ankle joint were 0.93 ± 0.21,1.33 ± 0.14,0.72 ± 0.10, 2.08 ± 0.59, respectively. The co-contraction level of left elbow joint and ankle joint was significantly higher than that of the right side (P<0.05). Conclusions High-level male speed climbers using Tomoa skip technique showed obvious sEMG characteristics, the contribution rate of upper limb muscles and latissimus dorsi were higher than that of lower limb. The activation mode of elbow joint was dominated by biceps brachii, and that of ankle joint was dominated by anterior tibial muscle. There exsited differences between left and right limbs in coordinated movement mode. The difference of contribution rate and activation level of upper limb between the left and right limbs was more than that of the lower limb.

Abstract:Objective To evaluate the test-retest reliability of the ballistic push-up (BPU) test and establish predictive models for upper-limb strength and explosive power in young males. Methods 71 male college students performed assessments of upper-limb bench press maximal strength (1 repetition maximum, 1RM), bench press explosive power, and two BPU tests with a 48-hour interval. BPU test data were recorded using a three-dimensional (3D) force platform and motion capture system to calculate concentric metrics such as peak force (PF) and mean velocity (MV). The intraclass correlation coef?cient (ICC) was used to examine the retest reliability of the BPU test. The Pearson correlation coef?cient was used to evaluate the correlation of the BPU metrics with upper-limb strength and explosive power. Predictive models for upper-limb strength and explosive power were created using stepwise regression analysis. Results BPU metrics showed a good test-retest reliability (ICC = 0.764–0.935). PF and MV, along with body weight (BW), were effective predictors of bench press 1RM in young males: bench press 1RM = 0.109PF-16.772 [R2 = 0.790, standard error of the estimate (SEE) = 8.17 kg]; bench press 1RM = 1.511BW+87.15MV- 110.136 (R2 = 0.767, SEE = 8.60 kg). PF and BW were also predictors of bench press explosive power: bench press explosive power = 2.755BW+0.287PF-17.351 (R2 = 0.620, SEE=46.1 W). Conclusions The BPU test demonstrates a good test-retest reliability, and PF and MV from the BPU test can be used to predict upper-limb strength and explosive power in young males.

Abstract:Objective To investigate the effects of transcranial direct current stimulation (tDCS) combined with resistance training on performance of the college students completing pull-ups, and explore the potential mechanisms underlying the effects of training intervention from the perspective of neuromuscular activity control. Methods A total of 25 male college student volunteers were randomly divided into the tDCS combined with resistance training group (experiment group) and resistance training group (control group). Twelve subjects in the control group received a lat pull-down strength training intervention lasting for 8 weeks, with 4 sets of 12 movement repetitions each, 3 times per week. Thirteen subjects in the experimental group received a 20-minute tDCS before the lat pull-up resistance training intervention. Lat pull-down isometric maximal voluntary contraction (MVC) force, lat pull-down maximal repetitions under 80% one-repetition maximum (1RM) loading, and conventional pull-up exercise were tested before and after the training intervention. Surface electromyography (sEMG) signals of the main exertion muscles of the upper limb were recorded during the pull-up exercise test. Results After the training intervention, the number of pull-ups completed by the experimental group and control group increased by 1.74 times and 1.42 times, respectively. Subjects in both groups showed significant improvements in their MVC and lat pull-down maximal repetitions under 80% 1RM loading. However, there were no statistical differences in these indicators betwenn groups. Activation levels of the agonist muscles brachioradialis, posterior deltoid, and pectoralis major were significantly decreased after the training compared to those before training for both groups. In addition, the coactivation level of the antagonist triceps brachii muscle in the experimental group significantly decreased from 0.50 ± 0.22 to 0.37 ± 0.09 after the training, while there was no significant change in the control group before and after the intervention. Conclusions Eight-week tDCS combined with resistance training and resistance training alone can significantly improve the pull-up performance of college students, which may be related to the fact that both types of training can significantly improve the active muscle contraction capacity. Combined with resistance training, tDCS is more effective in decreasing the coactivation level of triceps brachii during pull-ups and increasing the contraction efficiency of elbow joint muscles.

Abstract:Objective To establish a foot-weightlifting shoe coupling model, investigate the biomechanical effects of midsole material variations during pull phase of the snatch, optimize the key parameters of weightlifting shoes, and reduce the risk of foot and ankle injuries in athletes. Methods The foot-weightlifting shoe finite element model was constructed using the finite element method for simulation. Kinematic and dynamic data of the snatch movement were obtained using sports biomechanics methods. Statistical methods were employed to validate the effectiveness of the model and compare the impact of different midsole materials on foot stress distribution, bone stress, soft tissue stress, and midsole strain of the the athletes during pull phase of the snatch. Results When the midsole thermoplastic polyurethane (TPU) had an elastic modulus of 20 MPa, the peak foot stress was minimized. As the elastic modulus of the midsole TPU increased, the foot stress peak also increased. Bone stress was concentrated in the third, fourth, and fifth metatarsals of the forefoot, with the fourth metatarsal showing the peak stress. As the elastic modulus of the midsole increased, the peak stress in the metatarsal area gradually decreased, the peak stress in soft tissues gradually increased, and the strain in midsole decreased. Conclusions Midsole materials with an elastic modulus between 20–25 MPa have an advantage in reducing foot pressure and preventing bone injuries in the foot and ankle.

Abstract:Objective To explore the motor coordination characteristics of the attack leg of the athletes under scoring actions in the front roundhouse kick of competitive taekwondo, and provide a theoretical basis for coaches o formulate precise training strategies in stages and segments so as to enhance the efficiency and success rate of the athletes’movements. Methods Kinematic data and surface electromyography signals were collected from 15 elite Taekwondo athletes during different phases of the front roundhouse kick. The continuous relative phase (CRP) method was used to calculate the joint coordination and variability of continuous relative phase (VCRP), while non-negative matrix factorization and k-means clustering were used to analyze muscle synergy characteristics. Results The coupling of the neural launch phase was dominated by knee-ankle coupling in coronal axis and hip-ankle coupling in sagittal axis. The coupling of the kicking phase was dominated by hipknee, hip-ankle in coronal axis, and knee-ankle coupling in vertical axis. The coupling of the recovery phase was dominated by hip-knee, hip-ankle coupling in coronal axis, and knee-ankle coupling in sagittal axis. These coupling relationships remained relatively stable around 0 rad. Approximately 80. 0% VCRP remained stableacross all phases, with minor fluctuations occurring at phase transitions. A total of 4, 5, and 4 muscle synergy clusters were identified in neural launch, kicking, recovery phases, respectively. There were significant differences in the mean gap values among phases (P<0. 001). However, there were no significant differences in the mean sparsity values among phases (P>0. 05). Some muscle synergies were shared across phases, while others differentiated to form phase-specific coordination patterns. Conclusions Joint coordination in each phase exhibited 1 - 3 primary stable patterns with flexibility during transitions. Muscle coordination was dynamically adjusted throughout the motion, and a general muscle synergy pattern functioned consistently across different phases, whereas a differentiated muscle synergy pattern fulfilled the phase-specific functional demands. The neural launch and kicking phases should be focused on during training, with the emphasis on controling over critical points to optimize performance.

Abstract:Objective To assess the motor function of school-aged children with congenital muscular torticollis (CMT), and analyze the spatiotemporal parameters of their walking motion as well as the kinematic parameters of the trunk and lower limbs, so as to explore the potential long-term impact of CMT on the growth and development of children. Methods Using three-dimensional (3D) gait analysis technology, the gait of children with CMT was evaluated in detail and compared with that of normal children. The motion angles and ranges of the trunk, pelvis, hip, knee, and ankle joints, along with spatio-temporal parameters, were analyzed. Thirty-one children with CMT aged 6–12 years were recruited into the torticollis group, and 31 normal children of the same age range were included in the control group. The data of the torticollis group were divided into the healthy side and the affected side based on the side of the torticollis. Statistical analysis was performed among the three groups to calculate the differences in kinematic and spatio-temporal parameters. Results Compared with nomal children of the same age in the control group, significant differences were observed in the affected and unaffected sides of the torticollis group in terms of stride length, gait speed, percentage of support phase time, average ankle inversion angle during the swing phase, average ankle inversion angle during the support phase, average foot orientation angle during the support phase, average ankle internal rotation angle relative to the tibia during the stance phase, average knee valgus angle during the stance phase, average shoulder joint elevation, and shoulder joint height at landing. Specifically, the torticollis group had significantly lower stride length, gait speed, ankle inversion angle, knee valgus angle, and foot eversion angle in both the affected and unaffected sides compared to the control group, while the percentage of support phase time and the internal rotation angle of the foot relative to the tibia during the stance phase were higher than those in the control group. Conclusions For school-aged children with CMT, there are still residual manifestations of overall motor development abnormalities. These abnormalities also affect the non-affected side. Children with CMT have a relatively high risk of developing uneven shoulders, their overall walking efficiency is lower than that of normal children of the same age, and they exhibit lower limb motor abnormalities such as insufficient ankle joint stability.

Abstract:Objective To analyze muscle activation intensity in patients with knee osteoarthritis (KOA) during physical activity by applying surface electromyography (sEMG), and investigate the impact of fear of movement on lower limb muscle function in KOA patients. Methods A total of 30 KOA patients were selected and categorized into a high-fear group (n = 16) and a low-fear group (n = 14) based on the TSK-17 scale (Tampa Scale for Kinesiophobia) scores, with 14 healthy individuals serving as the control group. A wireless sEMG system was used to record sEMG signals of different muscles. Test activities included walking at normal speed, stairs ascent, and stairs descent. Muscle activation was normalized to maximal voluntary contraction (MVC) by calculating the root mean square (RMS) of the EMG signals to compare muscle activation under different conditions. Correlation analyses were conducted to evaluate the relationship between muscle activation and TSK-17 scores. Results During normal walking, the healthy limb side of the high-fear group showed significantly greater activation in the rectus femoris (P=0.02), vastus medialis (P<0.01), and vastus lateralis (P<0.01) compared to the affected limbside. Similarly, muscle activation was elevated during stair ascent in the high-fear group, with significant differences in the rectus femoris (P<0.01), vastus medialis (P<0.01), and vastus lateralis (P<0.01). Furthermore, in the high-fear group, the affected limb side exhibited significantly increased activation in the rectus femoris during normal walking compared to the low-fear group and control group. There was a significant positive association between TSK-17 scores and rectus femoris activation on the healthy limb side during stair descent (r=0.952, P<0.01).Conclusions Fear of movement has a significant impact on muscle activation patterns in KOA patients, particularly during stair descent, which places a greater functional demand on the lower limbs. Therefore, great attention should be paid to the intervention of psychological factors in KOA treatment, so as to comprehensively improve both motor function and life quality of the patients.

Abstract:Objective A biomechanical model of cervical kyphosis under the effects of axial traction load and lateral push load was establised, so as to provide a theoretical basis for the treatment of cervical curvature abnormalities, and formulate the most appropriate treatment plan for patients. Methods Based on the CT scan data of patients, the axial data of the cervical spine was extracted to fit the cervical curvature curve. Using the Timoshenko beam theory and the cervical rehabilitation training system, a mathematical model of cervical kyphosis was established for analytical calculations to obtain the recovery curve of the cervical spine under load and the total load required to cure cervical kyphosis, and its rationality was also verified. Results The biomechanical model of cervical kyphosis was established. Under the effects of axial traction load and lateral push load, the cervical spine effectively developed in the direction of physiological bending. The total axial load and lateral load were 353 N and 5 649 N, respectively, and the magnitude of the total axial load increased with the increase in traction angle. The therapeutic moment of the total lateral load decreased as the Bordon value increased. The therapeutic moment of the axial load was smaller than that of the lateral load in the range of normal Bordon value, confirming the rationality of the loads. Conclusions The established biomechanical model of cervical kyphosis can accurately simulate the biomechanical characteristics of the cervical spine, and the analysis results were valid, providing a mechanical theoretical basis for the design of treatment plans for patients.

Abstract:Objective To study the effects of regular Tai Chi exercise on bipedal standing balance control and its cortical electrical activity in older adults. Methods A total of 39 older adults were recruited. Among them, 18 subjects had regular Tai Chi training for 1–3 years (Tai Chi group), and 21 subjects did not have any form of regular exercise training (control group). The subjects in both groups were required to perform bipedal standing balance with their eyes open and closed for 60 s, and the center of pressure (COP) of the body and the electroencephalography (EEG) signals were captured during the balancing process. The sample entropy of COP was also calculated, and the EEG power in different brain regions at δ, θ, α and β frequency bands were calculated, and the correlation analysis of COP sample entropy and EEG power was performed. Results The entropy of the COPY sample of Tai Chi group during bipedal standing balance in eyes-open and eyes-closed states was significantly smaller than that of control group (P<0.05). In eyes-open standing balance task, the frontal-central-parietal region δ-wave and frontal-central region β-wave power of Tai Chi group were significantly higher than those of the control group (P<0.05). In eyes-closed standing balance task, the frontal-central-parietal region δ-, θ-, α-, and β- wave power were significantly higher than those of control group (P<0.05). In eyes-open standing balance task, the frontal (r=0.529), central-frontal (r=0.478), central (r=0.484), and central-parietal (r=0.488) α-wave power of Tai Chi group were positively correlated with the entropy of the COPLen sample (P<0.05), and in eyes-closed standing balance task, the central-parietal (r=-0.484), and parietal (r=-0.491) α-wave power were negatively correlated with COPLen sample entropy (P<0.05) . Conclusion Long-term regular Tai Chi exercise can stimulate more cortical involvement in postural control in older adults, and it can better regulate cortical α-wave rhythms and activities and optimize cortical control for better maintenance of body balance.

Abstract:Objective To investigate the effects of 16-week Tai Chi practice on muscle strength, plantar tactile sensation, kinesthesia, and postural control of older adults at different ages. Methods Thirty-nine older adults were divided into?60–75-year-old group (n=24) and the?76–90-year-old group (n=15), and both groups received Tai Chi practice for 16 weeks. The muscle strength, plantar tactile sensation, kinesthesia, and center of pressure root mean square (CoP-RMS) were measured before and after practice. Results After 16 weeks of Tai Chi practice, the fifth metatarsal head tactile sensation and ankle dorsiflexion/plantarflexion kinesthesia thresholds decreased in the?76–90-year-old group. However, there was no significant change in the 60–75-year-old group. The CoP-RMS in the medial/lateral direction decreased in the 60–75-year-old and 76–90-year-old group. Conclusions After 16 weeks of Tai Chi practice, muscle strength, plantar tactile sensation, kinesthesia, and postural control were improved. Especially for older adults aged over 75 years, Tai Chi practice improved plantar tactile sensation, kinesthesia, and postural control to a greater extent. Tai Chi practice provides a suitable and effective exercise form for older adults over 75 years.

Abstract:Objective To classify the foot types of young Chinese males, extract characteristic indicators of foot types, and construct a standard foot type database. Methods Foot type data from 1 483 healthy young male individuals were collected. Spectral clustering algorithm was utilized to categorize foot types, and a deep neural network (DNN) was employed for training the classification model. Layer-wise relevance propagation (LRP) and the correlation coefficient method were combined to extract foot type features, the differences in various foot type characteristics were compared. Results Spectral clustering yielded 4 distinct foot type categories. Foot type 1 was characterized by a high-arched foot with a prominent big toe, inwardly rotated 5th toe, and a high heel with a wide foot; foot type 2 was characterized by a narrow foot with hallux valgus; foot type 3 was characterized by a low-arched foot with hallux valgus; foot type 4 was characterized by a high-arched foot with a prominent big toe. By integrating interpretable neural networks and the correlation coefficient method, nine indicators were extracted from 27 foot type indicators, including the heel to the sole length, hallux height, navicular bone height, lateral malleolus height, hallux valgus angle, 5th toe angle, dorsal foot circumference, heel angle, and longitudinal arch angle. The classification model constructed with these extracted indicators achieved an overall discrimination accuracy rate of 93.67%, higher than the 86.91% achieved by linear discriminant analysis. Conclusions Chinese young males can be classified into four typical foot types. By examining the rearfoot, midfoot, and forefoot regions, nine key foot morphology parameters, including length, height, circumference, and angle, can be extracted. These parameters provide both theoretical and empirical support for establishing normative data on foot morphology for Chinese young males and for advancing biomechanical research on the foot and ankle.

Abstract:Objective Based on multi-objective optimization, a design method for Voronoi bionic porous scaffolds tailored to different extents of bone defects was proposed. Methods First, the effects of design parameters on mechanical and biological properties of the scaffolds were investigated. The response surface models were then established respectively for the design parameters and performance indicators (specific surface area, elastic modulus, yield strength, and permeability). Using a cubic scaffold with side length of 15 mm as an example (assuming a corresponding bone defect of the same dimension), multi-objective optimization of the scaffold was finally conducted using the non-dominated genetic algorithm-II algorithm, while considering the elastic modulus and permeability ranges of bone tissues as performance constraints. Results The degree of anisotropy in Voronoi scaffolds was influenced by the number of seed points, while the size and scaling factors of the scaffolds exclusively impacted the rod diameter and rod length. Using the design method of this study, the optimal scaffold with specific defect size satisfying mechanical and biological properties was obtained. The optimal scaffold under different strength requirements was obtained by adjusting the yield strength to change the utopia point. Conclusions A design method for Voronoi bionic porous scaffolds based on multi-objective optimization was proposed. This method can be applied to bone defects at different degrees and provides a new idea for the personalized design of bone tissue engineering scaffolds.

Abstract:Objective To explore the characteristics of fluid flow within loaded osteons under different boundary conditions. Methods The COMSOL Multiphysics software was used to establish a three-dimensional (3D) finite element model of osteons with different boundary conditions, and the variation rules of pore pressure and flow velocity of osteons under different inner wall pulsating blood pressure and outer wall elastic constraint conditions were analyzed. Results As the pulsatile blood pressure inside the osteon increased from 0 mmHg (1 mmHg=0.133 kPa) to 300 mmHg, the peak pore pressure within the osteon correspondingly increases from 26 kPa to 68 kPa. As the elastic constraint on the outer wall of the osteon changed from being completely elastic to completely constrained, the peak pore pressure within the osteon increased from 15 kPa to 26 kPa, and the peak flow velocity increased from 0.04 μm/s to 0.07 μm/s. Conclusions This study has clarified the influence laws of the changes in boundary conditions such as the pulsatile blood pressure on the inner wall and the elastic constraint on the outer wall of the osteon on the characteristics of fluid flow within the loaded osteon. These findings are conducive to a deeper understanding of the mechanical response mechanisms of bone tissues in both physiological and pathological states, and provide important theoretical bases for further research on bone mechanotransduction.

Abstract:Objective To establish and validate a human comfort evaluation method based on musculoskeletal activity in biomechanics. Methods Firstly, the limitations of current biomechanical-based comfort evaluation methods were analyzed. Secondly, a new evaluation method based on musculoskeletal activity was proposed, which considered? the influence of muscle and joint on comfort, and a comfort index was obtained. Finally, the firefighter’s water belt rolling task was selected for verification. Results The comfort index derived from the improved musculoskeletal activity-based evaluation method was 0.74, which was lower than the comfort index of 0.82 obtained from the comfort based on muscle activity. The verification results aligned with the theoretical analysis. A questionnaire survey conducted on 43 firefighters showed that the subjective assessments gathered were consistent with the verification outcomes, further confirming the conclusion that the former method was more comprehensive and accurate. Conclusions The comfort evaluation method that integrated both muscle and joint conditions better reflects the actual conditions of the human body. Compared to methods that focus solely on muscle, this approach was more effective at revealing potential biomechanical risks and had a greater practical significance.

Abstract:Objective The effect of sciatic neurectomy (SN) on the meso-mechanical properties of cortical bone was explored by combining animal modeling and resonant ultrasound spectroscopy. Methods A total of five New Zealand White rabbits underwent unilateral SN, and cortical bone specimens were obtained from the tibias on the operated and normal sides at 4th week after SN; multiple elastic constants (C11, C12, C13, C33, and C44), engineering mechanical parameters, and anisotropy ratios of the bone specimens were acquired using irregular resonant ultrasound spectroscopy under assumptions of transverse anisotropy, and the paired t-test was used to assess the differences in mechanical properties of the cortical bone between the two sides. Results Compared with the normal side, the elastic constants in different directions (C11, C12, C13, and C33) of the cortical bone on the operated side showed a decreasing trend, ranging from 8.49% to 32.23%; the axial elastic modulus (E3) and Poisson's ratio (v31) were reduced by 5.85% and 24.07%, respectively, but there was no significant changes in the anisotropic properties. Conclusion The method of cortical bone disuse modeling through SN is feasible. This method can significantly change meso-mechanical properties of the cortical bone, and the elastic constants can more comprehensively reflect the changes in mechanical properties of the cortical bone.

Abstract:Objective By exploring changes of six degrees of freedom (6DOF) kinematics of the knee joint during extra weight bearing of the body trunk, the influence of extra weight on knee joint movement patterns was studied. Methods A total of 24 healthy subjects were recruited to walk/run on a treadmill at four speeds under two states: self-weight and wearing a 16 kg vest, and gait analysis was conducted. A three-dimensional (3D) portable knee kinematics analysis system based on infrared stereophotography was used to capture 6DOF movement trajectory data of the tibia relative to the femur. Results Compared to the self-weight state, when additional trunk weight was added, the knee external rotation angle was reduced at 3.6 km/h speed (1.4°–2.1°) and 5.4 km/h speed (2.2°–2.7°) ; the knee internal rotation angle was reduced at 10.8 km/h speed (2.1°–4.2°); the knee flexion angles was increased significantly at the speed of 3.6 km/h (1.5°–1.8°), 9 km/h(1.6°–3.3°)和10.8 km/h (1.9°–3.1°); the knee adduction angle increased at 5.4 km/h speed (0.5°–0.6°), and decreased at 10.8 km/h speed (0.9°–1.3°). At 10.8 km/h speed, the distal knee displacement (0.2–0.4 mm) was increased, and the lateral knee displacement (0.1–0.2 mm), and anterior knee displacement (0.2–0.3 mm) were significantely reduced. Conclusions The 6DOF kinematics of human knee is significantly affected by the extra trunk weight. Performance is also different at lower and higher speeds. It is suggested that there may exist a hidden injury in military training, and this study provides a kinematic basis for the occurrence of sports injury.

Abstract:Objective To investigate the effect of active muscle response on mechanical responses and injuries of human neck under high Gx loading. Methods A refined finite element model of the head and neck with active muscle response was established and validated based on the existing post-crash volunteer experiments. The effects of active muscle action on the kinematic and biomechanical responses of the neck were investigated under different G-value loads and at each tilting angle using this model. Results The stress distribution of vertebrae under high Gx load was dispersed from C4–7 to the whole vertebrae, and the active muscle action reduced the stress change, and the effect was significant in the case of 8 G acceleration, which reduced the peak vertebral bone stress by 23.6% and 11.6%, and the peak intervertebral disc stress by 42.3% and 63.4% under 8 G and 10 G conditions, respectively. The maximum stress difference of 34.3 MPa was achieved by the active muscle action at 15° backward tilting. Conclusions The neck showed better stability by the active muscle action under the impact of high Gx load. At different tilting angles, the active muscle action was more obvious in the backward tilting posture compared with the forward tilting and upright seated postures, and the backward tilting posture was safer to meet the impact when the same active muscle action was applied. The results can provide a reference for the subsequent studies related to the neck injury.

Abstract:Objective To investigate the distribution of plantar pressures and bone stresses of the foot with high, normal and low arch shapes, and reveal the influence of arch morphology on foot biomechanical properties. Methods A total of 127 young women were recruited. The foot type was classified by collecting the morphological data of the foot with the three-dimensional (3D) foot scanner, and three types of the foot arch morphology were selected for analysis, The geometric model of foot bone was obtained by CT scanning, so as to establish the biomechanical finite element model of the foot. A load of 50% human body weight was applied to the model to simulate the state of bipedal standing. Results Comparing the calculated plantar contact area with the measured results, the relative error values were smaller than 10%, which proved the validity of the finite element model. The peak plantar pressure under three types of arch morphologies was located in the hind foot region, and the heel pressure of high- and low-arched foot was higher than that with normal-arched foot. Compared with normal-arched foot, high-arched foot showed a significant increase in stress in the hind foot area, the peak stress of soft tissue was 299.45% higher, and the peak stress of bone was 93.19% higher. For low-arched foot, the plantar contact area increased by 13.28% and calcaneal stress increased by 98.09%. The peak bone stresses of high-, normal- and low-arched foot were located at the talus, which were 9.903, 19.921 and 36.308 MPa, respectively. Conclusions This study supports the association between abnormal arch morphology, foot pain and foot diseases, and provide a basis and direction for the design of orthopedic insoles and arch support structures for abnormal feet.

Abstract:Objective To make comparative analysis on mechancial properties of the modified cortical bone trajectory (MCBT) nailing technique using a novel variable-diameter screw and the traditional pedicle nailing technique using the cement-augmented pedicle screw (CAPS) in the L4 vertebral body. Merthods CAPS and MCBT instrumentation in the L4 vertebral body model were established by obtaining CT scan data from osteoporotic patients. The finite element method was used to compare the stability, screw axial pull-out force and lumbar spine motion under four working conditions (upper, lower, left and right loads) by using different nailing techniques. Results The axial pull-out force of the screws in MCBT group was 25.3% higher than that of the CAPS group (P<0.05); the load-displacement ratios of the screws in MCBT group were 14.9% (P>0.05), 23.2% (P>0.05), and 19.1% (P<0.05) higher than those of CAPS group under the lower, left, and right working conditions, respectively; the load-displacement ratios of the screws in MCBT group were slightly lower than those of CAPS group under the upper working condition, but the differences were not statistically significant (P>0.05); under the anterior and posterior flexion conditions, the lumbar spine motion of MCBT group was reduced by 13.3% and 2.5%, respectively, compared with CAPS group; under the left lateral bending, right lateral bending, and axial rotational conditions, the lumbar spine motion of MCBT group was improved by 69.1%, 74.6%, and 118.1%, respectively, compared with CAPS group, but these difference were not statistically significant (P>0.05). Conclusion MCBT screw was slightly better than CAPS in axial resistance to extraction force, and stability of vertebral anterior flexion under lower, left and right working conditions, and slightly weaker than CAPS in stability under upper, left lateral bending, right lateral bending, and axial rotational working conditions. This study demonstrates that MCBT screw has certain advantages over CAPS, and it provides a pre-basic foundation for the clinical application of MCBT nailing technique for treating osteoporosis.

Abstract:Objective To explore the biomechanical characteristics of different types of lumbar disc herniation, and provide a theoretical basis for the clinical classification, diagnosis, and treatment of LDH. Methods A normal lumbar spine model with spinal nerves and four types of LDH models (central type, paracentral type/lateral recess type, intervertebral foramen type, extreme type) were constructed, and the biomechanical characteristics of the intervertebral discs and nerve roots in neutral posture and six degrees of freedom conditions were analyzed. Results In neutral position, the stress of normal intervertebral disc was greater than that of the herniated intervertebral disc, and the stress ratio of annulus fibrosus and nucleus pulposus in normal model was greater than that of annulus fibrosus and nucleus pulposus in herniated models. In neutral position, the disc stress was mainly concentrated at the incisor between the protrusion and normal part, and recruitment occurred at outer edge of the disc. In flexion and extension position, the stress of the herniated intervertebral disc shifted to the ritht side. The maximum stress of herniated intervertebral disc appeared during right flexion condition, and the nerve root stress on the right side was greater than that on the left side. The stress of the herniated intervertebral disc during right rotation condition was slightly lower than that during right flexion condition, and the stress of nerve root on the right side was smaller than that on the left side. Conclusions The intervertebral disc is important in maintaining lumbar dynamic and static stability and flexibility. Different positions have an obvious effect on the stress of the intervertebral disc. For patients with LDH, forward bending, flexion of the affected side and large extension should be avoided. Appropriate rotation of the affected side can help relieve the symptoms of nerve root compression.

Abstract:Objective To investigate the the effects of fracture fragment size and fixation method on the biomechanical stability of distal tibial epiphyseal injuries in children. Methods A three-dimensional (3D) finite element model of a Salter-Harris II (SH-II) epiphyseal injury with fracture fragments of varying sizes (Small, Middle, Big) was constructed using computed tomography (CT) data from the lower limb of a 10-year-old volunteer. and bone-internal fixation assemblies were created with 1–3 screws ( 1S group, 2S group, 3S group) and Kirschner wire (K group). The model was subjected to gravitational forces, posterior drawer forces, and external rotation. Displacement and stress distributions on fracture fragments and fixation devices were analyzed. Results The maximum displacement for the four groups of models was concentrated at the distal end of the fracture fragment. Under gravity conditions, the maximum displacement of the distal end of the fracture fragment in the 1S, 2S, 3S and K models in the Small group was 5.69, 5.57, 5.56, 0.11 mm, respectively, and the bone stress was 16.95, 12.26 , 8.57 and 5.00 MPa, respectively. A high stress area at the epiphyseal plate and the fracture line was easily formed under screw fixation, while a high stress area at the edge of the epiphyseal plate was formed under Kirschner wire fixation. Conclusions When distal tibial epiphyseal injuries in children are treated by using screws, increasing the number of screws can improve the fixation stability and share local bone stress, but the connection area between the fracture fragment and the epiphyseal plate cannot be too small. Kirschner wire fixation can provide better biomechanical effects than screw fixation.

Abstract:Objective Through in vitro experiments, biomechanical data of the transtibial pullout suture (TPS), tendon reconstruction (TR), and tendon reconstruction with suture augmentation (TRS) were collected, so as to evaluate the biomechanical effectiveness of tendon reconstruction for repairing medial meniscus posterior root tear (MMPRT). Methods Eighteen porcine knee joint models were divided into three groups, TPS, TR, and TRS. TPS group: sutures were used to fix the meniscal root. TR group: tendons were passed through an incision at the meniscal root. TRS group: tendons were passed through an incision at the meniscal root and secured at tendon-meniscus contact area with additional sutures. The sutures and tendons were pulled out through tibial tunnels and fixed at the anteromedial tibia. All groups underwent failure load tests, and ultimate failure load, displacement at failure load, load at clinical failure, stiffness, and failure modes of the samples were recorded. Results The ultimate failure load in TPS group was significantly higher than in TR group (P<0.05), but there was no significant difference between TPS group and TRS group (P>0.05). The ultimate failure load in TRS group was significantly higher than in TR group (P<0.05). The displacement at failure load in TR group and TRS group was significantly lower than that in TPS group (P<0.05), but there was no significant difference between TR group and TRS group (P>0.05). There were no significant differences in the load at clinical failure among the 3 groups (P > 0.05). The stiffness of TRS group was significantly greater than that of TPS group (P<0.05), but no significant difference was observed between TR group and TPS group, as well as between TR group and TRS group (P>0.05). All failures were caused by suture or tendon cutting through the meniscus. Conclusions The tendon reconstruction techniques is superior to the TPS in terms of failure displacement and stiffness,while the TRS further enhances the stability of the repair. This study provides an important clinical reference.

Abstract:Objective To establish a hydraulic system model of the aqueous humor circulation in the human eye and explore the characteristics of aqueous humor flow and intraocular pressure changes under various types of glaucoma and surgical conditions. Methods A hydraulic system model of aqueous humor circulation was constructed using AMESim software based on ocular structural parameters to simulate the fluid dynamics of aqueous humor in three types of glaucoma and their surgical interventions. Results Significant elevation in intraocular pressure was observed with pathological changes such as trabecular meshwork obstruction, anterior chamber angle contraction, and narrowing of the iris-lens gap. Through simulations of surgical interventions, including trabeculectomy, iridectomy, and ciliary body ablation, aqueous outflow resistance was effectively reduced, leading to a controlled intraocular pressure. Conclusion By successfully simulating both the pathological conditions of glaucoma and the dynamic intraocular pressure changes under surgical interventions, the hydraulic system model accurately reflects the physiological characteristics of glaucoma. The model not only predicts the effects of therapeutic interventions, but also provides reliable simulation support for the diagnosis and optimization of treatment strategies for glaucoma.

Abstract:Objective To analyze the biomechanical responses after small incision lenticule extraction (SMILE) based on personalized biomechanical parameters of the human eye. Methods Through the results from the correlation analysis between corneal stromal elastic modulus and biomechanical parameters, the cornea elastic modulus was predicted and the material parameters were obtained. Based on clinical measurement data, 52 personalized myopic human eye models were reconstructed to analyze the corneal biomechanical response after SMILE. Results The biomechanical response of the cornea varied from patients, and the vertex displacement and stress of the corneal surface increased or decreased after SMILE. On average, when residual stromal thickness (RST) ranged from 278 μm to 332 μm and IOP was 16–20 mmHg, the change of vertex displacement and stress on the corneal surface after SMILE were less than those under IOP=11–16 mmHg. Under RST＞332 μm and IOP=11~16 mmHg, the corneal biomechanics was relatively stable. In addition, the corrected diopters of patients increased, and the deformation of corneal surface after SMILE was more drastic. Conclusions RST and IOP are important influencing factors in corneal biomechanics. The material parameters of corneal tissues were predicted based on corneal biomechanical parameters. The cutting profiles and surgical parameters of SMILE may be optimized through analyzing the surgical effect after refractive surgery with the reconstructing personalized finite element model of human eyes.

Abstract:Objective To use a physics-informed neural network (PINN)-based model to predict hemodynamics in intracranial aneurysms and address the long simulation time and high computational cost of traditional computational fluid dynamics (CFD) simulations. Methods The PINN model was trained using only the computational domain coordinates and sparse velocity measurement points from CFD data of clinical patients. The predicted blood flow velocity, pressure, and wall shear stress (WSS) from the PINN model were compared with CFD simulation results. Results The proposed method was used to test and validate data from four different patients. For velocity prediction, the average mean absolute error (MAE) , average mean relative error (MRE) , average mean squared error (MSE) was 4.60%, 6.61%, and 0.229%, respectively. For WSS prediction, the average MAE, MRE and MSE was 5.54%, 8.58%, and 0.510%, respectively. The PINN model demonstrated good generalization capability across different aneurysm models and could reduce the computation time of hemodynamics from several hours to just a few seconds. Conclusions The PINN model can effectively compensate for incomplete measurement data through physical constraints, even when boundary conditions are unknown and measurement data are sparse. It can rapidly and accurately simulate the hemodynamics of intracranial aneurysms. This method has the potential to provide effective support for clinical risk prediction in intracranial aneurysms.

Abstract:The application of mechanics in clinical wound healing has a long history; however, the systematic underlying mechanisms remain unclear. With recent advancements in biomechanics and mechanobiology, the principles regarding how mechanical factors influence the formation, progression, and healing of wounds have gradually been elucidated. Herein, based on progress in theories, technologies, and clinical practices concerning the interplay between mechanics and wound healing, this study introduces the concept of wound-repairing mechanomedicine. Relevant research is systematically reviewed from the perspectives of biomechanics, mechanobiology, and mechanotherapy. Additionally, potential future development directions are prospectively analyzed to provide novel insights into wound care and strategies for preventing scar formation.

Abstract:The incidence of cardiopulmonary vascular diseases is extremely high and mechanic stress plays an important role in vascular remodeling. Reactive oxygen species (ROS) at physiological levels modulate cell signaling while excessiveROS trigger oxidative stress and induce injury. The types of mechanical stresses in the vascular system and the sources of ROS were summarized. Besides, the roles and mechanisms of mechanical stress-induced oxidative stress in cardiopulmonary vascular diseases were discussed. This review will facilitate a deeper understanding of vascular activity and disease development at the molecular level, provide potential targets for treating vascular diseases. In addition, there are still research gaps on the mechanism of oxidative stress induced by mechanical stress in vascular diseases. Therefore, the potential research direction of mechanical stress-induced oxidative stress in the cardiopulmonary vascular system is also predicted, which may promote the development of mechanobiology to a certain extent.

Abstract:Foot torsion stiffness refers to the foot’s ability to resist deformation when subjected to twisting forces, and such characteristics play a crucial role in preventing sports injuries and informing the design of athletic footwear. This review systematically summarizes the biomechanical research progress of foot torsion and shoe torsion, as well as the research and application of multi-segment foot models in foot-shoe torsion. The findings indicate that foot torsion stiffness significantly impacts lower limb kinematics, kinetics, and athletic performance. Optimizing this stiffness can improve stress distribution, reduce injury risk, and enhance performance. The future researches should focus on refining measurement techniques to enhance reliability and efficiency in clinical applications, providing a scientific foundation for sports injury prevention and footwear design.

Abstract:Lumbar manipulation plays an important role in the non-surgical treatment of lumbar degenerative diseases. Lumbar manipulation technique is a compound technique that contains many mechanical elements and motion characteristics at the moment of operation. Quantifying and objectifying the parameters of traditional Chinese medicine massage techniques, summarizing the technical characteristics of the operation, and discussing the biomechanical mechanism of the manipulation in-depth, can contribute to the teaching assessment and clinical diagnosis and treatment standards of massage techniques, making the manipulation more safe and efficient, and further promoting the inheritance and development of traditional Chinese medicine massage. This article reviews and compiles domestic and foreign biomechanical research papers on lumbar massage for the treatment of lumbar degenerative diseases in recent years. The biomechanical effects on the lumbar spine and its accessory structures under manual transient loading, the measurement of technical parameters, and the characteristics of manual operation were summarized.

Abstract:Hydrogels are an important direction in the field of biomedicine in recent years. Their biocompatibility, biodegradability and biomechanical properties make them ideal materials for the clinical treatment of skin wounds, and they have important research and clinical application values. As a high water content three-dimensional (3D) network structure polymer material with many unique biomechanical shapes, hydrogel has the potential to be applied to skin wounds with many mechanical properties, such as elasticity, viscoelasticity, dynamic stiffness and adhesion, which can not only protect the wound surface after artificial adjustment, but also help to simulate the mechanical microenvironment of biological tissues during healing. Then the function and behavior of cells are regulated to promote cell regeneration, strengthen tissue repair and functional recovery. At the same time, the biomechanical mechanism of skin wound healing is complex, and there are still many challenges in the clinical treatment of skin wounds with hydrogels. Future studies will further focus on the mechanism of biomechanical properties in skin wound healing. In conclusion, hydrogels are expected to be more widely used in the clinical treatment of skin wounds due to their unique mechanical properties. In this review, recent research progress on biomechanical properties of hydrogels is summarized, including regulatory mechanisms and their clinical application in promoting skin wound repair, the importance of studying these properties for the design of tissue engineering scaffold materials is emphasized, and the design, use and clinical transformation of mechanically regulated wound healing is prospeced.