OBJECTIVE:This study investigated the effects of chronic ankle instability (CAI) on postural control following landing with an unanticipated task and on shank-rearfoot coordination during side-cutting in female soccer players. The association between postural stability and coordination patterns was investigated to identify shared control characteristics across tasks. METHODS:Eighteen female soccer players were categorized into CAI (n = 10) and control (n = 8) groups. Participants performed 20-s single-leg stances and side-cutting following landing with an unanticipated task. Postural control during single-leg stance was quantified using the largest Lyapunov exponent of the mediolateral center of pressure. Shank-rearfoot coordination during side-cutting was analyzed using a modified vector-coding technique. RESULTS:The CAI group exhibited a significantly lower largest Lyapunov exponent of mediolateral center of pressure during single-leg stance (p = .043). During side-cutting, the CAI group demonstrated an increased proportion of in-phase with distal dominancy during the deceleration phase (p = .027). Within the CAI group, largest Lyapunov exponent was associated with coordination patterns, where a negative correlation with anti-phase with proximal dominancy and a positive correlation with in-phase with distal dominancy (r = -.680 and .648, respectively; p < .050) were observed. CONCLUSION:Female soccer players with CAI exhibit reduced adaptability to postural control following landing with an unanticipated task and diminished flexibility in shank-rearfoot coordination during sport-specific cutting. The observed association between static postural instability and altered dynamic coordination may reflect a reduced capacity to flexibly modulate control strategies in patients with CAI, which may be related to the risk of recurrent ankle sprains.

This study utilized uncontrolled manifold (UCM) analysis to investigate the covariation structure of segment angles involved in the mediolateral and vertical stabilization of the center of mass (COM) during stair descent at different speeds in healthy young adults. Twenty-nine individuals participated in this study. Spatiotemporal and kinematic data were collected during the stair descent task. The swing phase was divided into the first half and second half of swing phases, and UCM analysis was performed to determine the covariation structure of segment angles that stabilize the mediolateral and vertical COM. The results showed that during the first half of swing phase, variability stabilizing the vertical COM was enhanced. In the second half of swing phase, while variability stabilizing the mediolateral COM was enhanced, variability that destabilizes the vertical COM is also enhanced. In conclusion, the findings suggest that different motor strategies are adopted for COM stabilization depending on the phase and speed of stair descent. These results contribute to a better understanding of stair descent from the perspective of COM coordinates.

INTRODUCTION:The risk of spondylolysis increases in children and adolescents involved in sports that involve trunk extension, such as marching bands. Prolonged posture while playing musical instruments may lead to musculoskeletal disorders. Although many scholars have studied the effects of playing posture on lumbar-pelvic kinematics, few have focused on marching band performance. PURPOSE:This study assessed the influence of basic posture during marching band performance on lumbar-pelvic kinematics. METHODS:The participants were healthy young adults without musculoskeletal injuries. Gait was measured under three conditions using a three-dimensional movement analysis system: normal gait, gait with a 1.15 kg trumpet, and marching band performance. An analysis of a single right gait cycle was used in this study to compare the spatiotemporal parameters and joint angles between conditions. RESULTS:The mean values of the thoracic posterior tilt angle, thoracolumbar transition, lumbar extension angle, and anterior pelvic tilt angle in forward marching were significantly higher than those in free walking and instrument-grasping gait (p < .05). The change in the thoracic and lumbar rotation angles in forward marching was significantly lower than those in free walking (p < .05). DISCUSSION:Forward marching may increase lumbar extension, heighten shear forces, and activate the erector spinae muscles. Restricted upper limb swing may hinder the coordination of the erector spinae muscles and impair trunk stability. CONCLUSION:Increased trunk/pelvic extension and decreased trunk rotation during forward marching may lead to overloading of the erector spinae muscle. Attention to posture during marching may help prevent low back pain.

This study investigated postural control following unanticipated single-leg landings in female soccer players with and without chronic ankle instability (CAI). Eighteen female soccer players, including 10 CAI and 8 healthy controls, participated in the study. They completed three successful 20-second single-leg stances following an unanticipated jump landing. Angular variations of the rearfoot, midfoot, and forefoot in the frontal and sagittal planes, as well as center of pressure (COP) data including total trajectory length, mean velocity, range, and time-to-boundary (TTB) in both the medial-lateral (ML) and anterior-posterior (AP) directions were collected during the single-leg stance task. The CAI group demonstrated significantly greater midfoot angular variation (0-5 s: p = 0.043; 5-20 s: p = 0.017), higher COP ML velocity (p = 0.002), and a longer COP trajectory length (p = 0.021). The mean of TTB minima in the ML direction was also significantly lower in the CAI group (0-5 s: p = 0.018; 5-20 s: p = 0.035). These findings suggest that female soccer players with CAI demonstrated impaired postural control following unanticipated landings, likely due to sensorimotor deficits. Incorporating spatiotemporal measures such as TTB may improve postural control assessments in individuals with CAI.

Background Patients with knee osteoarthritis exhibit greater knee muscle co-contraction, and which in turn is a risk factor for disease progression. Objective The aims of this study were to assess the muscle co-contraction during walking and quadriceps exercises in patients with medial knee osteoarthritis, and to identify the factors most associated with the alterations in co-contraction. Methods The subjects were 12 women with medial knee osteoarthritis and 13 asymptomatic controls. Kinematic and kinetic parameters during walking, and co-contraction indices during walking, knee extension and straight leg raising exercises were measured. The factors associated with the alteration in co-contraction in the osteoarthritis group were determined by linear regression analyses. Results Compared with the control group, the osteoarthritis group showed significantly greater co-contraction of the vastus lateralis and biceps femoris (VLBF) in two quadriceps exercises as well as the VLBF, co-contraction of the vastus lateralis and lateral gastrocnemius (VLLG) in walking. In linear regression analyses, the VLBF and VLLG in walking were associated with knee extension moment and knee pain frequency in daily life. The VLBF in knee extension and straight leg raising exercise were associated with knee flexion angle in a quiet standing position and knee varus peak angle during the stance phase of walking. Conclusions Greater muscle co-contractions were observed in not only walking but quadriceps strengthening exercises in patients with knee OA. Besides, the factors of these patterns were different in different tasks. These findings may help the development of more effective rehabilitation strategies for patients with knee osteoarthritis.

Background: Numerous ankle sprains have been reported in female players performing noncontact play such as side-cutting maneuvers. This study examined the coordination between foot joints during unanticipated side-cutting maneuvers in female soccer players under various cutting angles. Methods: Twelve healthy female soccer players performed unanticipated side-cutting maneuvers in three directions (anterolateral, lateral, and posterolateral). The stance phase was time-normalized and categorized into three phases, namely loading response, deceleration, and propulsion. A modified vector coding technique was used to quantify the coupling angle between the rearfoot, midfoot, and forefoot on the cutting side, which indicates intra-joint coordination, and categorizes the angle into four distinct coordination patterns. Results: Compared with anterolateral cutting maneuvers, posterolateral cutting maneuvers considerably increased the proportion of in-phase with distal dominancy in the rearfoot vs. midfoot (p ​= ​0.011) during the loading response and in-phase with proximal dominancy in the midfoot vs. forefoot (p ​= ​0.049) during the propulsion phase. During sharp-angle side-cutting maneuvers, the ankle dorsiflexion angle decreased (anterolateral vs. posterolateral: p ​< ​0.001, lateral vs. posterolateral: p ​= ​0.005), and the ankle inversion angle increased (anterolateral vs. lateral: p ​< ​0.001) in most of the stance phase. Conclusions: The intra-foot coordination pattern of the ankle joint during unanticipated side-cutting maneuvers with sharper angles indicated an increased risk of lateral ankle sprain.

Total knee arthroplasty (TKA) is widely recognized as an effective procedure for reducing pain, improving activities of daily living (ADLs), and enhancing the quality of life in elderly patients with advanced knee osteoarthritis (KOA). However, many patients continue to have trouble with stair descent after TKA, a key functional movement that significantly affects postoperative satisfaction. This report describes the case of an 80-year-old woman with bilateral KOA who underwent left TKA. Despite undergoing postoperative rehabilitation, she continued to experience functional impairments and fear while stair descending, prompting the initiation of outpatient physiotherapy. Initial evaluations (78 days post-surgery) revealed limited range of motion (ROM) in the knee joint, muscle weakness, and high levels of anxiety and fear of movement, as measured by patient-reported outcome measures (PROMs). Surface electromyography (EMG) further identified abnormal muscle activity in the semitendinosus muscle and medial head of the gastrocnemius. Outpatient physiotherapy was performed twice a week and focused on improving ROM, strengthening the quadriceps and hamstrings, performing knee ROM exercises and mobilization, and providing guidance on independent home training. At the final evaluation (118 days post-surgery), knee ROM improved, and the PROMs score demonstrated enhanced self-efficacy. However, anxiety and fear of movement persisted. In terms of muscle strength, no significant improvement was observed. Additionally, the swing phase was extended, and EMG during stair descent revealed increased muscle activity in the semitendinosus and medial head of the gastrocnemius, suggesting compensatory protective muscle activity due to residual fear of movement. In addition to physical factors, such as knee ROM and quadriceps muscle strength, psychosocial factors, such as fear, anxiety, and depression, are critical components influencing outcomes after TKA. Residual fear is believed to delay ROM improvement and contribute to protective-like muscle activity. This case highlights the importance of a comprehensive rehabilitation approach addressing both physical and psychological aspects to optimize functional recovery in TKA patients with a pronounced fear of movement.

Background and Objectives: According to the well-established correlation between knee joint contact force and external knee adduction moment (KAM) during walking, many studies have focused on gait modifications that target changes in the frontal plane, such as foot progression and trunk inclination angles, to decrease KAM. However, recent research has highlighted the relationship between the external knee flexion moment (KFM) and knee joint contact force, highlighting the importance of considering both the KAM and KFM in gait modifications that highlight changes in the sagittal plane. Consequently, the current study aimed to investigate the effects of increasing knee joint flexion angle while walking on knee joint loading. METHODS:This study was a cross-sectional study. 20 healthy older adults each performed two gait conditions - normal walking and walking with a 10-degree increase in the maximum flexion angle, with five trials conducted for each condition. RESULTS:The results showed that increasing the flexion angle significantly reduced KAM. Specifically, the first peak KAM decreased from 0.59 ± 0.24 to 0.43 ± 0.26 N·m/kg·m (p < 0.001), and the second peak KAM from 0.57 ± 0.20 to 0.45 ± 0.25 N·m/kg·m (p = 0.002). Conversely, the peak KFM increased significantly from 1.5 ± 0.48 to 1.8 ± 0.51 N·m/kg·m (p < 0.001). Furthermore, gait modification involved a straightforward intervention-merely providing verbal instructions to slightly increase knee flexion angle-making it both feasible and practical for older adults at higher risk of developing osteoarthritis of the knee (knee OA). CONCLUSIONS:Ensuring sufficient knee joint flexion angle during the early stance phase may serve as an effective instructional strategy for reducing KAM. Given its simplicity and non-invasive nature, this intervention may have practical potential for use in clinical or community-based gait training programs for older adults at risk of knee OA. However, these findings should be interpreted with caution when generalized to patients with knee OA. Such individuals may have altered muscle activation, increased joint sensitivity, or limited range of motion, which could affect their response to gait modification. Future studies involving longitudinal follow-up or patient-centered outcomes such as pain, function, and adherence will be necessary to evaluate the long-term clinical applicability of this intervention.

Background: Varus thrust (VT) is a frequently reported abnormal gait pattern in patients with medial knee osteoarthritis (KOA). VT is important to prevent KOA progression. However, there is no consensus on the relationship between VT and foot alignment and flexibility, although it has been reported that patients with KOA have pronated foot. Objective: In this study, we examined the relationship between VT, foot alignment, and flexibility in patients with KOA. Methods: Twenty patients with unilateral KOA were included in this study (mean age: 71.5 +/- 4.7 years). KOA severity ranged from grade III (8 patients) to grade IV (12 patients) based on the Kellgren-Lawrence classification. Gait analysis using inertial sensors was performed to determine the difference between the VT of KOA side and the contralateral side without symptoms. The correlations between VT, foot alignment, and flexibility were also analyzed. Results: VT was significantly greater on the side with KOA than on the contralateral side without KOA (d = 1.09, p = .002). VT was not significantly correlated with foot alignment but was significantly correlated with the arch stiffness index, which indicates foot flexibility (r = 0.642, p = .003). Conclusion: This study suggests that foot flexibility may play a more significant role than foot alignment in addressing VT in patients with KOA. When performing physical therapy for VT, evaluating foot flexibility in addition to foot alignment may help reduce this condition. Further studies with larger sample sizes and more detailed statistical analyses are needed to validate these findings.

Purpose: This study aimed to quantify multi-segmental coordination using Uncontrolled Manifold (UCM) analysis to examine the effect of speed reduction on the control of stair descent.Methods: Twenty healthy participants performed stair descent at a self-comfortable pace for normal speed conditions and at a slow speed set to a metronome rhythm of 60 beats/min. UCM analysis was separately conducted for the center of mass (COM) and swing foot, with anteroposterior and vertical movements designated as task variables, and segment angles defined as elemental variables. Delta V, the normalized difference between the variance in segment angle that does not affect task performance (VUCM) and the variance that does affect task performance (VORT) was calculated separately for the COM and swing foot and compared between normal and slow speeds.Results: The VORT for the COM and the swing foot in the anteroposterior direction were significantly lower at slow speeds than at normal speeds. The VORT of task-relevant segment angles affecting COM control in the vertical direction was significantly higher at slow speed compared to normal speed. Additionally, the Delta V in segment angle variance impacting swing foot control in the anteroposterior direction was significantly greater at slow speed than at normal speed.Conclusions: The findings suggest that descending stairs at reduced speed promotes enhanced coordination of lower limb segments for controlling the swing foot in the anteroposterior direction, while concurrently increasing segmental variability that destabilizes the vertical COM.

[Purpose] The effect of heel lift insertion on gait in patients who have undergone total hip arthroplasty (THA) with patient-perceived leg length difference is seldom referenced in the literature. We used an AB design to investigate the alterations of gait function before and after inserting a heel lift on the non-operative side. [Participant and Methods] The participant had a patient-perceived leg length difference after THA and presented with gait disturbance. The survey phase was 10 days (phase A: normal physiotherapy for five days, and phase B: normal physiotherapy and heel lift insertion for another five days) from the 17th day following THA. The ambulatory task was conducted at a self-determined, comfortable pace and objectively assessed using an inertial sensor. [Results] The insertion of a heel lift partially improved the gait symmetry and the ratio of lumbar acceleration in three directions; it also corrected the patient-perceived leg length difference. [Conclusion] An investigation was carried out to examine the impact of a heel lift on gait in a single case of THA with patient-reported leg length difference. The application of a heel lift may enhance the relationship between the patient-perceived leg length difference, gait symmetry, and the ratio of lumbar acceleration in three dimensions.

Objective: The purpose of this study was to examine the longitudinal changes in trunk acceleration, gait speed, and paretic leg motion in patients with post-stroke hemiparesis, the relationships between variables at each time point, and whether initial trunk acceleration and gait parameters were related to gait speed 2 months later. Methods: Gait was assessed monthly in patients who could walk under supervision after stroke onset. Gait parameters, including gait speed and trailing limb angle (TLA), were measured. Trunk acceleration was quantified using acceleration root mean square (RMS) and stride regularity (SR) indices. Results: This study found statistically significant longitudinal changes in gait speed (p < .001), acceleration RMS of the total axes (p < .001), and SR of the vertical axes (p < .001). Gait speed correlated significantly with the acceleration RMS of the mediolateral (r = -0.815 to -0.901), vertical (r = -0.541 to -0.747), and anteroposterior (r = -0.718 to -0.829) axes, as well as the SR of the vertical axes (r = 0.558 to 0.724) at all time points from T0 to T2. For the TLA, only the acceleration RMS of the mediolateral axis correlated significantly over the entire study period (r = -0.530 to -0.724). In addition, initial TLA correlated significantly with gait speed after 2 months (r = -0.572). Conclusion: This study showed that assessing trunk acceleration helps estimate the improvement in gait status in patients with post-stroke hemiparesis. The magnitude and regularity of trunk acceleration varied longitudinally and were related to gait speed and paretic leg motion at each time point; however, they could not predict future changes in gait speed.

Lateral ankle sprains have a high recurrence rate, often developing into chronic ankle instability (CAI). CAI affects movement strategy during side-cutting maneuvers, with inconsistent results in many studies. This study aimed to clarify the characteristics of movement strategies during side-cutting maneuvers in female soccer players with and without CAI. Thirteen female soccer players with CAI and twelve healthy controls performed 10 successful trials of side-cutting maneuvers in three directions (anterolateral, lateral, and posterolateral) under unanticipated conditions. Compared to the control group, the CAI group displayed an increased stance time in the lateral and posterolateral side-cutting maneuvers (lateral: p=0.021, effect size=0.97, posterolateral: p=0.014, effect size=1.00). In posterolateral side-cutting maneuvers, the CAI group displayed a decreased posterior ground reaction force at 19-30% and 42-54% of the entire stance phase compared with the control group (p=0.001, effect size=1.30-1.42). Female soccer players with CAI may display increased stance time to compensate for self-reported ankle instability and may also exhibit decreased braking and propulsive force when side-cutting to sharper angles. These observations suggest a hypothesis that could help in the assessment of cutting maneuvers under unanticipated conditions after ankle sprains.

Background Squatting is commonly used in various settings to enhance muscle strength and performance. Both fast and slow squats have advantages as training to improve muscle function in the lower extremity muscles. Movement speed affects the variability of interjoint coordination and decreased variability can lead to overuse injuries owing to repetitive mechanical loading on the lower extremity joints. However, only a few studies have focused on interjoint coordination during squatting. This study aimed to clarify the kinematic and kinetic differences, as well as the interjoint coordination, during squatting at different speeds. Methodology Healthy young participants with no locomotor disease were recruited to perform descending parallel squats at different speeds (one, three, and five seconds) using a 3D motion analysis system and force plates. Joint moments and continuous relative phases were calculated and compared between the conditions. Results There were no significant differences in the mean values of lower limb joint moments among the three speed conditions. However, the mean absolute values of the continuous relative phase between the ankle and hip joints and the mean standard deviation of the continuous relative phase between each lower limb joint were significantly lower in the high-speed condition than in the medium- and low-speed conditions. Additionally, in the high-speed condition, the knee joint moved ahead of the hip joint in the knee-hip joint phase coordination pattern. Conclusions The joint load per unit time remained constant across all speed conditions. High-speed squatting may adapt to mechanical loading on the joints, although the knee joint moves ahead of the hip joint, exhibiting a highly coordinated movement. Conversely, low-speed squatting may reduce the risk of disability owing to the high variability of interjoint coordination. Therefore, squatting training should be based on individual characteristics and objectives.

Introduction Anomalous gait after total hip arthroplasty (THA), marked by increased trunk lateral flexion during weight-bearing, is a noteworthy aspect to consider for enhancing ambulatory capacity. One potential training modality that is feasible in the early post-THA period is lateral weight shifting during double-leg standing. However, the influence of physical therapists’ instructional guidance on trunk lateral flexion and hip abductor muscle activity in this context remains unclear. Purpose To investigate the influence of physical therapist’s guidance directed towards reducing the trunk lateral flexion angle during lateral weight-shifting in double-leg standing post-THA. Methods Twenty THA patients, assessed at 2 weeks postoperatively, performed lateral weight-shifting under two conditions: the normal condition and the instructed condition, for comparison. The latter involved tactile and verbal guidance guidance to minimize trunk lateral flexion. Patients were categorized based on trunk flexion direction for comparison, exploring the correlations between hip abductor muscle activity and kinematic parameters. Results In the instructed condition, a significant reduction in trunk lateral flexion and increased hip lever arm length were observed compared to those in the normal condition. Patients with trunk flexion towards the operated side exhibited a notable reduction, while those on the non-operated side showed no significant changes. Gluteus medius muscle activity correlated with trunk lateral flexion, and tensor fasciae latae muscle activity correlated with body's center of mass lateral displacement and hip adduction angle. Conclusions Physical therapist’s guidance influenced lateral weight-shifting in double-leg standing post-THA. Differences in the trunk lateral flexion direction may lead to different effects from the guidance.

This case report describes a woman in her fifties who experienced a left-sided atherothrombotic cerebral infarction with lesions in the left corona radiata. The patient exhibited motor paralysis of the right upper and lower limbs. After a 10-day acute hospital stay, she was admitted to a rehabilitation facility for an intensive program of physical, occupational, and speech therapy. By day 17 of the onset, she had achieved independence by walking with a cane. This case was documented to study the effects of gait training with non-paretic knee immobilization on muscle activity and trunk kinematics in post-stroke hemiplegia. Traditional physical therapy was used initially, followed by an intervention phase in which gait training was performed with the non-paretic knee immobilized. This approach was hypothesized to induce beneficial kinematic and muscle activity changes in the paretic limb. The results showed increased muscle activity in the paretic lateral gastrocnemius without compromising trunk stability, suggesting that this method may improve rehabilitation outcomes in similar cases.

Background A decrease in knee flexion excursion during the loading response may affect not only quadriceps muscle weakness, pain, and inflammatory symptoms, but also lead to physical function decline and activity limitation. The aim of this investigation was to clarify the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function in patients with knee osteoarthritis. Methods Twenty patients diagnosed with medial knee osteoarthritis. The participants walked along a 10 m corridor in the laboratory at a comfortable pace. The kinematic and kinetic data were collected using a 3D motion analysis system. We employed to control for gait speed and age while examining the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function. Findings Knee flexion excursion showed a significant positive correlation with the peak and angular impulse of knee flexion moment. In the partial correlation coefficients controlling for age and gait speed, significant negative correlations were found between knee flexion excursion and knee adduction moment angular impulse. Interpretation It can be inferred that gait with reduced knee flexion movement during the loading response in patients with knee osteoarthritis may result in increased mechanical stress on the knee joint in the frontal plane. Exercise interventions aimed at increasing knee flexion excursion may result in a reduction in disease progression.

Background Malignant femoral soft tissue tumors are occasionally resected together with the femoral nerves, but this can cause loss of knee extensor muscle activity. To the best of our knowledge, no previous reports have detailed the gait analysis of such cases in combination with electromyography. Herein, we report the gait analysis of a patient who underwent left groin synovial sarcoma and left femoral nerve resection 12 years ago. Case presentation We analyzed the gait of a 38-year-old man who was able to walk unaided after the resection of a synovial sarcoma in the left groin together with the ipsilateral femoral nerve. The muscle activities of the affected medial (MH) and lateral hamstrings (LH), and lateral heads of the gastrocnemius (GL) were increased during 50–75% of the stance phase. The hip flexion angle of the affected limb was smaller, and the ankle plantar flexion angle of the affected limb was larger than that of the non-affected limb. This means that in the affected limb, the hip and ankle angles were adjusted to prevent knee collapse, and the MH, LH, and GL muscles contributed in the mid- and late-stance phases. Moreover, we found that the hamstring and gastrocnemius of the affected limb worked together to keep the ipsilateral knee extended in the mid-stance phase and slightly flexed in the late-stance phase. Conclusions Patients capable of walking after femoral nerve resection may control their hamstrings and gastrocnemius muscles collaboratively to prevent ipsilateral knee collapse in the mid- and late-stance phases.

This study investigated the covariate structure of each segmental angle that stabilize the center of mass (COM) in the mediolateral and vertical directions in response to knee joint movement in individuals with knee osteoarthritis (KOA) using uncontrolled manifold (UCM) analysis. Twenty individuals with KOA and 13 healthy controls participated in this cross-sectional study. Kinematic and kinetic data were collected during level walking. UCM analysis was used to determine the covariance structure of segment angles stabilizing the COM in the mediolateral and vertical directions. The results indicated reduced knee flexion movement during the stance phase in the KOA group. In the mediolateral direction, the KOA group exhibited increased kinematic synergy stabilizing the COM. However, in the vertical direction, decreased kinematic synergy was observed. KOA group demonstrated greater trial-to-trial variances in segmental angles constituting the knee joint, suggesting enhanced covariance structure attempting to stabilize the COM in the mediolateral direction but increasing variability that destabilizes the COM in the vertical direction. Furthermore, decreased knee flexion movement during loading response may lead to reduced vertical kinematic synergy. In conclusion, these findings underscore the need to address improving knee flexion movement during the loading response to prevent osteoarthritis progression in patients with KOA. It provides insights into interventions focusing on improving knee flexion and enhancing kinematic synergy in the vertical direction, potentially benefiting patients with KOA.