BACKGROUND: Changes in the center of body weight during standing reflects the structure, function and muscles of the lower limbs and even the whole body. The relationship between standing posture control and foot type, balance ability, and muscle activation is rarely reported. OBJECTIVE: To investigate the effects of natural, lean forward and lean backward standing on foot arch, body balance and muscle activation. METHODS: Fifteen subjects without foot lesions and diseases related to foot function were selected. Three-dimensional foot scanner was used to test and analyze the foot arch in three standing postures. BTS FREEMG 300 surface electromyography tester and balance tester were used to test and analyze the maximum root mean square of muscle and two balance ability indexes (envelope area and average velocity of center of gravity) in three standing postures. RESULTS AND CONCLUSION: (1) For height index of foot arch: there was significant difference between natural standing and forward standing (P ＜ 0.05). There was significant difference between natural standing and backward standing (P ＜ 0.05), but there was no significant difference between forward standing and backward standing (P＞ 0.05). (2) The degree of muscle activation was as follows: when standing naturally, the medial peroneal muscles＞ erector muscles＞ rectus abdominis＞ gluteus medius＞ biceps femoris＞ external oblique femoris＞ anterior tibial muscle＞ rectus femoris muscle＞ gluteus maximus muscle. During forward standing: the medial of the peroneal muscle＞ medius gluteus＞ vertical ridge＞ long head of biceps femoris＞ anterior tibial muscle＞ rectus abdominis muscle＞ gluteus maximus. During backward standing: the obliquus externus femur＞ rectus femoris＞ long head of biceps femoris＞ erector spinae＞ musculus rectus abdominis＞ the medial of the peroneal muscle＞ gluteus medius＞ gluteus maximus. (3) Balance: there was no significant difference between natural standing and forward standing (P＞ 0.05); there was significant difference between natural standing and backward standing (P ＜ 0.05), but there was no significant difference between forward standing and backward standing (P＞ 0.05). (4) In summary, it is easy to maintain body stability at low muscle activation intensity when the human body is standing naturally. During the body backward standing, the muscle activation intensity is highest due to instability. When the center of gravity moves forward and backward, the contralateral muscle is mainly activated. The arch of the foot rises when it leans forward and backward. The slight anterior and posterior movements of the center of gravity in the standing posture can lead to changes in muscle activation degree and balance control.

Objective To investigate the relationship between plantar pressure and plantar sensation in people with different foot types and provide theoretical references for injury evaluation and sports recovery in patients with flat feet.Methods Recruited participants were initially screened using a three-dimensional(3D)foot scanner.They were divided according to the arch index as follows:16 in the normal foot group and 16 in the flat foot group.Plantar pressure and sensation tests were performed in different groups using the Footscan high-frequency plantar pressure test system and the Semmes-Weinstein monofilament test,respectively.The test results were analyzed for statistical descriptions and correlations.Results The plantar pressure impulses of the left and right arches and the medial area in the flat foot group increased significantly compared with those in the normal foot group(P＜0.05).The plantar sensory thresholds of the first metatarsal bone and arch position in the flatfoot group were lower than those in the normal foot group(P＜0.05).There was a significant positive correlation between left foot sole sensation,right foot arch position,and plantar pressure in the flat foot group.Conclusions The structural features of reduced arches and excessive valgus in people with flat feet result in increased plantar pressure impulses and lower thresholds of plantar sensory sensitivity in the arch and medial heel positions.Meanwhile,there is a correlation between plantar sensation and plantar pressure;the greater the load of plantar pressure,the lower the threshold of plantar sensation.

Objective By establishing finite element model of the proximal femur, the injury risk of proximal femur under the conditions of self-selected speed rise and rapid rise at initial stage of standing during sit-to-stand (STS) transition was analyzed.Methods CT images of proximal femur in the elderly were processed with three-dimensional (3D) reconstruction and reverse modeling, so as to complete the solid model. The finite element model was established through material assignment and meshing. Based on the finite element analysis software ANSYS, the boundary conditions were constrained, and 1.733 kN and 1.837 kN loads were applied to obtain stress distributions and strain of proximal femur at different rising speeds. Results The stress concentrated at medial edge of the greater trochanter and the femoral neck. The peak stress and micro-strain appeared on inner edge of the larger rotor. The peak stress was 30.16 MPa and peak micro-strain was 2 553.5 at rapid rising speed. The peak stress and peak micro-strain at self-selected rising speed were 28.69 MPa and 2 430.4, respectively, which were relatively lower. For stress concentration area of femoral neck, the stress ranges at rapid rising speed and self-selected rising speed were 13.42-23.46 MPa and 12.76-25.51 MPa, respectively.Conclusions Frequent STS transition may increase the risk of fatigue fractures for proximal femur in the elderly. Rapid STS transition has a higher injury risk for proximal femur than STS transition at self-selected speed.

Objective To evaluate the difference of foot-ankle function for subjects with different foot types from both dynamic and static aspects by means of sports biomechanics, so as to provide theoretical support and references for the study of foot-ankle movement. Methods According to the arch index, 65 subjects were divided into three groups: flat foot, low arch foot and normal foot. One-way ANOVA was used to analyze the difference of static and dynamic foot-ankle function indexes among the three groups. Results In terms of static foot-ankle function, the malleolar valgus flexibility (MVF) of normal foot and ankle was significantly higher than that of low arch foot and flat foot (P<0.05), while in terms of arch height flexibility (AHF), the effect of weight bearing on normal foot was smaller than that of flat foot (P<0.05), but there was no significant difference in transverse arch flexibility (TAF) among the three groups. In terms of dynamic foot-ankle function, the force offset amplitude and time of normal foot at buffer stage were higher than those of the other two groups (P<0.05), and at transition stage, the transition time of normal foot was significantly lower than that of low arch foot and flat foot (P<0.05). At pedal-extension stage, the pedal-extension time and speed of normal foot were significantly higher than those of flat foot (P<0.05). Conclusions The posture maintenance ability and longitudinal arch shape maintenance ability of low arch foot and flat foot are worse than those of normal foot with the load increasing, and the arch rigidity and plantar elasticity of low arch foot and flat foot are worse than those of normal foot, and normal foot shows better load-bearing cushioning ability, elastic-to-rigid transition ability and pedal extension efficiency during walking. A systematic and comprehensive evaluation system is of great significance to the prediction of foot-ankle injury risk and the evaluation of sports ability.

BACKGROUND:Research on foot and ankle proprioception is crucial for the rehabilitation of chronic ankle instability and geriatric diseases as well as for the improvement of body posture control and motor performance.Previous studies have often studied the sensory evaluation of the foot and ankle joints separately,which has limitations for a comprehensive understanding of their sensory function. OBJECTIVE:The foot and ankle complex is the only part in direct contact with the support surface,and plays an important role in the collective sensory feedback and regulation and balance control.By combing the existing investigation and research of foot and ankle ontology,the measurement and evaluation methods of the sensation of the foot and ankle complex are combed,in order to pave the way and provide the theoretical basis for future related studies. METHODS:Chinese terms"(foot OR foot ankle OR ankle)AND(sensation OR proprioception)"and English terms"(foot OR ankle)AND(feel OR proprioception)"were used as the keywords for retrieving relevant literature in the Web of Science,PubMed,and CNKI.We understood the basic concepts,current status and scope of research on the foot and ankle,summarized and evaluated the proprioceptive evaluation methods of the foot and ankle,and finally included 57 papers for further review. RESULTS AND CONCLUSION:The evaluation of foot and ankle complex sensation was mainly divided into sensory evaluation of the foot and proprioceptive evaluation of the ankle joint.The sensory evaluation of the foot mainly describes the sensation of the skin and the sensory feedback under the intervention conditions.The methods mainly include the pressure sensory threshold test,the two-point discrimination test of the foot(planar and plantar),and the duration test of skin vibration sensation.Ankle joint proprioception evaluation focuses on the description of joint position,motion range,force value and functional performance.The methods are mainly divided into static joint angle reset test,motion minimum threshold test,force perception reproduction test and dynamic balance,speed and walking ability tests.The report of quantitative results is generally expressed by"an error,"which is generally divided into absolute error,relative error,constant error,etc.To conclude,the foot and ankle complex has specific sensory capabilities,including foot sensation and ankle proprioception,which affect the quality of life and athletic performance of humans.Weakness of both foot sensation and ankle proprioception is associated with reduced human balance,and the combined measurements of the two can comprehensively and effectively evaluate foot and ankle function.The combination of foot and ankle sensory measures is selected according to different research needs and various influencing factors such as environment,emotion and reporting style are fully considered,to improve the validity of measurement and evaluation.

Objective:To explore the characteristics of arch function in patients with flexible flat foot by comparing the differences of static and dynamic arch function between normal and flexible flat foot patients,provide theoreti-cal reference for the functional distinction of different types of foot arch. Method:Thirty adult male subjects were recruited.Normal and flat feet were distinguished by foot printing method,and flexible flat feet were screened by heel raising test and passive toe raising test.Sixteen normal feet and fourteen patients with flexible flat feet were screened.Static arch stiffness was calculated by the differ-ence of arch height between natural standing and sitting at different loading positions,and the relative arch height at the beginning of the middle support period,change value of relative arch height,change rate of rela-tive arch height and proportion of middle foot impulse during walking were evaluated by 3D motion capture and plantar pressure.The correlation between static arch stiffness and dynamic arch function was analyzed by partial correlation(controlling step speed). Result:The static arch stiffness of flexible flat feet was lower than that of normal feet(P＜0.05).The results of dynamic arch function test showed that the relative height and change rate of arch height in the middle of walking support decreased gradually in both normal and flexible flat feet,the change value and change rate of arch height in flexible flat feet at the beginning of the middle of walking support period were lower than those in normal feet(P＜0.05).The proportion of impulse of flexible flat feet in walking support was higher than that of normal feet(P＜0.05).Partial correlation analysis showed that the relative height,relative height change value and relative height change rate at the beginning of middle support were positively correlated with static arch stiffness(r=0.580-0.679,P＜0.05),the proportion of middle foot impulse was negatively correlat-ed with static arch stiffness(r=-0.478,P＜0.05). Conclusion:During walking,the arch of the foot continued to decline in the middle of support,and the rate of decline gradually decreased.The adaptability of static and dynamic arches to loading in patients with flexi-ble flat feet was lower than that of normal feet.It is the key of ankle rehabilitation to improve the weight bearing adaptability of arch in patients with flexible flat foot.Arch stiffness is correlated with dynamic arch function,which is an important reference value for the functional division of different types of foot arch.

Objective To explore the patterns of functional gait asymmetry during the support phase and the differentiation of bilateral foot functions,to gain insights into the human movement compensa-tion mechanisms and stability control characteristics,so as to provide theoretical references for the pre-vention and rehabilitation treatment of unilateral foot and ankle injuries.Methods Twelve young females with normal feet were recruited,and the time percentage of each phase of the support period,the change of longitudinal arch angle,the vertical ground reaction force and the center of plantar pressure trajectory of the dominant and non-dominant feet were collected by using a three-dimensional motion capture and a high-frequency plantar pressure testing system when the subjects walked at the optimum speed with the incremental loading of weights[0%body weight(BW),10%BW and 20%BW].The ef-fects of laterality(dominant foot,non-dominant foot)and load(0%BW,10%BW,20%BW)on arch changes and gait parameters,and the interactions between them,were analyzed using a two-way re-peated-measures ANOVA.Results The factors of laterality and load interacted significantly on arch changes,but not on gait parameters.(2)Compared with 0%BW,the time percentage of the buffering phase of the nondominant feet with the load of 20%BW increased(P<0.05),while that of the domi-nant ones decreased(P<0.05),with an increase in the buffering load of both feet with the load of 20%BW(P<0.05)and the buffering force excursion of both feet with the load of 10%BW(P<0.05).More-over,changes in longitudinal arch angle increased(P<0.05)with the load of 10%and 20%BW,the pedal extension load rate increased(P<0.05)with the above BW load in the non-dominant feet,and the horizontal slope of pedal extension decreased(P<0.05)with 20%BW load in the dominant feet.Compared with 10%BW,when the feed was loaded 20%BW,the time percentage in the buffering phase and the buffering force offset of the dominant feet decreased(P<0.05),while the buffering load of both feet increased(P<0.05).(3)Compared with the non-dominant feet,for the dominant feet,the buffering load rate at the load of 10%and 20%BW and changes in the longitudinal arch angle at the load of 20%BW decreased(P<0.05),while the horizontal slope of the pedal extension without load in-creased(P<0.05).Conclusion Walking with load induces function differentiation in bilateral feet.The dominant foot has more efficient horizontal extension without load and better buffering function in the vertical direction with loads,while the non-dominant feet perform a more adequate weight-bearing and extension function vertically with larger load.It is suggested that unilateral injury feet should not be given too much load,and it is inappropriate to select a single foot to represent and evaluate the func-tion and injury risk of the double feet in loaded walking.