Validity of AI-Based Gait Analysis for Simultaneous Measurement of Bilateral Lower Limb Kinematics Using a Single Video Camera.

Accuracy validation of gait analysis using pose estimation with artificial intelligence (AI) remains inadequate, particularly in objective assessments of absolute error and similarity of waveform patterns. This study aimed to clarify objective measures for absolute error and waveform pattern similarity in gait analysis using pose estimation AI (OpenPose). Additionally, we investigated the feasibility of simultaneous measuring both lower limbs using a single camera from one side. We compared motion analysis data from pose estimation AI using video footage that was synchronized with a three-dimensional motion analysis device. The comparisons involved mean absolute error (MAE) and the coefficient of multiple correlation (CMC) to compare the waveform pattern similarity. The MAE ranged from 2.3 to 3.1° on the camera side and from 3.1 to 4.1° on the opposite side, with slightly higher accuracy on the camera side. Moreover, the CMC ranged from 0.936 to 0.994 on the camera side and from 0.890 to 0.988 on the opposite side, indicating a "very good to excellent" waveform similarity. Gait analysis using a single camera revealed that the precision on both sides was sufficiently robust for clinical evaluation, while measurement accuracy was slightly superior on the camera side.

Validity of muscle activation estimated with predicted ground reaction force in inverse dynamics based musculoskeletal simulation during gait.

The inverse dynamics based musculoskeletal simulation needs ground reaction forces (GRF) as an external force input. GRF can be predicted from kinematic data. However, the validity of estimated muscle activation using the predicted GRF has remained unclear. Therefore, the purpose of this study was to determine the validity of estimated muscle activation with predicted GRF in the inverse dynamics based musculoskeletal simulation. To perform musculoskeletal simulations, an open-source motion capture dataset that contains gait data from 50 healthy subjects was used. CusToM was used for the musculoskeletal simulations. Two sets of inverse dynamics and static optimization were performed, one used predicted GRF (PRED) and another used experimentally measured GRF (EXP). Pearson's correlation was calculated to evaluate the similarity between EMG and estimated muscle activations for both PRED and EXP. To compare PRED and EXP, paired t-tests were used to compare the trial-wise muscle activation similarity and residuals. Relationships between joint moments and residuals were also tested. The overall muscle activation similarity was comparable in PRED (R = 0.477) and EXP (R = 0.475). The residuals were 2-4 times higher in EXP compared to PRED (P < 0.001). The hip flexion-extension moment was correlated to sagittal plane residual moment (R = 0.467). The muscle activations estimated using predicted GRF were comparable to that with measured GRF in the inverse dynamics based musculoskeletal simulation. Prediction of GRF helps to perform musculoskeletal simulations where the force plates are not available.

Abductor hallucis muscle activity during short foot exercise in combination with static and dynamic functional tasks.

BACKGROUND: Short foot exercise (SFE) can be combined with dynamic functional tasks such as squats; however, it is unclear whether this combination increases intrinsic foot muscle activity. RESEARCH QUESTION: This study aimed to investigate and compare the abductor hallucis muscle (AbdH) activity during SFE in static and dynamic functional tasks. METHODS: The AbdH electromyography data of 17 healthy participants with and without SFE were analyzed during static tasks (sitting, double-leg standing, and single-leg standing) and dynamic tasks (double-leg squat, single-leg squat, split squat, and heel-raise). The static tasks were performed with SFE for 5 seconds, and the dynamic tasks were performed while performing SFE. AbdH activity with or without SFE during the task was compared using the Friedman and Wilcoxon signed-rank tests. RESULTS: AbdH activity was significantly greater in conditions with SFE than in those without SFE for all tasks (P < 0.01) except for heel-raise (P = 0.163). AbdH activity during SFE in single-leg standing was significantly higher than that in sitting, double-leg standing, and double-leg squats (P < 0.05). AbdH activity during SFE in the single-leg squat was also significantly greater than that in the sitting position (P = 0.024). No significant differences were found in any other between-task comparisons of AbdH activity during SFE. AbdH activity during tasks without SFE revealed significantly lower levels for sitting and double-leg standing compared to single-leg squat, split squat, and heel-raise (P < 0.001). Additionally, the activity in double-leg squat was significantly lower than in both single-leg squat and heel-raise (P < 0.05). SIGNIFICANCE: Combining dynamic tasks, except for the heel-raise task, with SFE can increase AbdH activity more than dynamic tasks without SFE. However, clinicians should note that combining dynamic tasks with the SFE may not increase AbdH activity compared to combining static tasks with the SFE.

Fear-Avoidance Beliefs Associated with Non-Specific Chronic Low Back Pain in College Athletes.

Purpose: This study aimed to determine the psychosocial factors associated with non-specific chronic low back pain (NS-CLBP) among college athletes. Material and Methods: A cross-sectional study was performed at one university. A non-anonymous, self-administered online questionnaire was collected from each athlete. Participants with a history of orthopaedic spine disease or surgery were excluded. Online responses from 368 college athletes belonging to 18 clubs were collected, among which 263 were included in the analysis. In the 263 responses, 41 individuals were identified as having NS-CLBP. Multivariate logistic regression analyses were performed to determine factors associated with presence of NS-CLBP. Independent variables included the Fear-Avoidance Beliefs Questionnaire physical activity subscale (FABQ-PA) score, Tampa Scale for Kinesiophobia-11 (TSK-11) score, Roland-Morris Disability Questionnaire (RDQ) score, and body mass index (BMI). Additionally, the Mann-Whitney U-test was utilized to compare FABQ-PA, TSK-11, RDQ scores, and BMI between the NS-CLBP and non-NS-CLBP groups. Results: The FABQ-PA (odd ratio = 1.096, P = 0.003) was significantly associated with NS-CLBP. No significant association was observed between NS-CLBP and TSK-11 (P = 0.776), RDQ (P = 0.074), and BMI (P = 0.296). The scores for FABQ-PA, TSK-11, RDQ, and BMI in the group with NS-CLBP were found to be significantly higher compared to the group without NS-CLBP (P < 0.001, P = 0.034, P < 0.001, and P = 0.022, respectively). Conclusion: The present study revealed a significant relationship between higher FABQ-PA scores and NS-CLBP among college athletes. Conversely, TSK-11 and BMI values showed no significant association with NS-CLBP presence. The findings suggest that addressing fear-avoidance beliefs may be crucial in managing NS-CLBP among college athletes.

Relationship among the COM Motion, the Lower Extremity and the Trunk during the Squat.

Squatting is a common motion in activities of daily living and is frequently used in training programs. Squatting requires a shift of the body in both vertical and anterior-posterior directions. Postural control during squatting is considered a mixed strategy; however, details and roles of the trunk and lower limb joints are unclear. The purpose of this study was to investigate the relationship among the kinematics of the lower limb, the trunk and the center of mass (COM) descent during squatting. Twenty-six healthy young adults performed repeated parallel squats. Lower limb joint and trunk angles and the COM were analyzed using a 3D motion analysis system. We evaluated the relationship between the kinematics and the squat depth by performing correlation analysis and multiple linear regression analysis. The ankle was the first to reach its maximum angle, and the remaining joints reached their maximum angles at the maximum squat depth. The knee joint motion and the squat depth were significantly correlated and there was a correlation between the hip and the ankle joint motion and the anteroposterior displacement of the COM during squatting. Multivariate linear regression analysis indicated that squat depth was predicted by both the knee and ankle motion and that anteroposterior displacement of the COM was predicted by the hip, ankle, and knee joint motion. The knees contributed to the vertical COM motion during squatting, while the hips contributed to the COM motion in the anteroposterior direction. On the other hand, the ankles contributed to COM motions in both the vertical and anteroposterior directions during squatting.

Estimation of Vertical Ground Reaction Force during Single-leg Landing Using Two-dimensional Video Images and Pose Estimation Artificial Intelligence.

OBJECTIVE: Assessment of the vertical ground reaction force (VGRF) during landing tasks is crucial for physical therapy in sports. The purpose of this study was to determine whether the VGRF during a single-leg landing can be estimated from a two-dimensional (2D) video image and pose estimation artificial intelligence (AI). METHODS: Eighteen healthy male participants (age: 23.0 ± 1.6 years) performed a single-leg landing task from a 30-cm height. The VGRF was measured using a force plate and estimated using center of mass (COM) position data from a 2D video image with pose estimation AI (2D-AI) and three-dimensional optical motion capture (3D-Mocap). The measured and estimated peak VGRFs were compared using a paired t-test and Pearson's correlation coefficient. The absolute errors of the peak VGRF were also compared between the two estimations. RESULTS: No significant difference in the peak VGRF was found between the force plate measured VGRF and the 2D-AI or 3D-Mocap estimated VGRF (force plate: 3.37 ± 0.42 body weight [BW], 2D-AI: 3.32 ± 0.42 BW, 3D-Mocap: 3.50 ± 0.42 BW). There was no significant difference in the absolute error of the peak VGRF between the 2D-AI and 3D-Mocap estimations (2D-AI: 0.20 ± 0.16 BW, 3D-Mocap: 0.13 ± 0.09 BW, P = 0.163). The measured peak VGRF was significantly correlated with the estimated peak by 2D-AI (R = 0.835, P <0.001). CONCLUSION: The results of this study indicate that peak VGRF estimation using 2D video images and pose estimation AI is useful for the clinical assessment of single-leg landing.

Effect of suspensory strategy on balance recovery after lateral perturbation.

Postural stability is essential for performing daily activities and preventing falls, whereby suspensory strategy with knee flexion may play a role in postural control. However, the contribution of the suspensory strategy for postural control during sudden lateral perturbation remains unclear. We aimed to determine how suspensory strategy contributed to postural adjustment during sudden perturbation in the lateral direction and what knee flexion setting maximized its effect. Eighteen healthy young adults (10 male and 8 female) participated in this study. Kinematic data during lateral perturbation at three velocities (7, 15, and 20 cm/s) were collected under three knee flexion angle conditions (0°, 15°, and 65°) using motion capture technology. Postural adjustments to the external perturbation were assessed by four parameters related to the temporal aspects of the center of mass (COM): reaction time, peak displacement/time and reversal time, and minimum value of the margin of stability (minimum-MOS). Our results showed that the COM height before the perturbation significantly lowered with increasing knee flexion angle. The COM reaction times for low and mid perturbation velocities were delayed at 65° of knee flexion compared to 0° and 15°, and the COM reversal times were significantly shorter at 65° of knee flexion than at 0° and 15° across all perturbation velocities. The minimum-MOS at the high-velocity of perturbation was significantly smaller at 65° of knee flexion than at 0° and 15°. In conclusion, the adoption of a suspensory strategy with slight knee flexion induced enhanced stability during sudden external and lateral perturbations. However, excessive knee flexion induced instability.

Relationship between onset of trunk muscle activities and pelvic kinematics in individuals with and without chronic low back pain.

BACKGROUND: Lumbopelvic movement patterns during prone hip extension has been proposed as a clinical screening method for trunk muscle dysfunction in patients with chronic low back pain (CLBP). However, correlations between trunk muscle onset and pelvic kinematics have not been investigated. OBJECTIVE: To examine the correlation between trunk muscle onset and pelvic kinematics during prone hip extension in participants with CLBP. METHODS: Fifteen patients with CLBP and 15 healthy individuals participated. We evaluated the muscle activities of the lumbar multifidus, the longissimus, and the semitendinosus via electromyogram and the displacement angles of the pelvic tilt, oblique and rotation. RESULTS: The onset of the multifidus at the ipsilateral side of hip extension was significantly delayed in the patients with CLBP compared to the control group (P< 0.001). The onset of the ipsilateral multifidus in the control group was significantly correlated with increased anterior pelvic tilt angle (P= 0.019, r= 0.597), whereas no significant correlation was observed in the CLBP group (P= 0.810, r=-0.068). CONCLUSION: The results suggest that pelvic kinematics during prone hip extension does not predict the delayed trunk muscle onset in patients with CLBP.

The relationship between joint kinematic patterns during single-leg drop landing and perceived instability in individuals with chronic ankle instability.

BACKGROUND: Perceived instability is a primary symptom among individuals with chronic ankle instability. However, the relationship between joint kinematics during landing remains unclear. Therefore, we investigated the relationships between landing kinematics and perceived instability in individuals with chronic ankle instability. METHODS: In 32 individuals with chronic ankle instability, we recorded ankle, knee, and hip joint angles during a single-leg drop landing. Joint angle waveforms during 200 ms before and after initial contact were summarized into single values using two methods: peak joint angles and principal component scores via principal component analysis. Using Spearman's rank correlation coefficient (ρ), we examined the relationships of peak joint angles and principal component scores with the Cumberland Ankle Instability Tool score, with a lower score indicating a greater perceived instability (α = 0.05). FINDINGS: The second principal component scores of ankle angle in the horizontal and sagittal planes significantly correlated with the Cumberland Ankle Instability Tool score (Horizontal: ρ = 0.507, P = 0.003; Sagittal: ρ = -0.359, P = 0.044). These scores indicated the differences in the magnitude of angles before and after landing. Significant correlations indicated a greater perceived instability correlated with smaller internal rotation and plantarflexion before landing and smaller external rotation and dorsiflexion after landing. In contrast, no peak joint angles correlated with the Cumberland Ankle Instability Tool score (P > 0.05). INTERPRETATION: In individuals with chronic ankle instability, ankle movements during landing associated with perceived instability may be a protective strategy before landing and potentially cause ankle instability after landing.

Trunk Muscle Activity and Ratio of Local Muscle to Global Muscle Activity during Supine Bridge Exercises under Unstable Conditions in Young Participants with and without Chronic Low Back Pain.

Core exercises on an unstable surface increase trunk muscle activity, especially for local muscle groups. Therefore, there is a possibility that exercises on an unstable surface would be effective in the rehabilitation of non-specific chronic low back pain (NSCLBP). The present study assessed trunk muscle activities during bridge exercise on the floor and two kinds of unstable surfaces, i.e., a balance ball and the BOSU, for individuals with and without NSCLBP. This study enrolled 17 and 18 young participants with and without NSCLBP, respectively. In the balance ball condition, both groups showed a significant increase in erector spinae activity compared to the floor condition, and the increase in activity was significantly greater in the NSCLBP group than in the control group (p = 0.038). On the other hand, neither group showed significant changes in trunk muscle activities in the BOSU condition compared to those in the floor condition. The control group showed a significant increase in internal oblique/transversus abdominis activity under the balance ball condition (p = 0.020), whereas there were no significant changes in these muscle activities between the balance ball and floor conditions in the NSCLBP group. The present study showed that participants with NSCLBP significantly increased muscle activity of the erector spinae, one of the global back muscles, on the balance ball in spite of small effects on muscle activity of the internal oblique/transversus abdominis, which is one of the local abdominal muscles. Therefore, attention should be paid to the application of bridge exercises on the balance ball for individuals with NSCLBP.

Development of a Conversion Table Linking Functional Independence Measure Scores to International Classification of Functioning, Disability, and Health Qualifiers: Insights from a Survey of Healthcare Professionals.

In clinical practice, patient assessments rely on established scales. Integrating data from these scales into the International Classification of Functioning, Disability, and Health (ICF) framework has been suggested; however, a standardized approach is lacking. Herein, we tested a new approach to develop a conversion table translating clinical scale scores into ICF qualifiers based on a clinician survey. The survey queried rehabilitation professionals about which functional independence measure (FIM) item scores (1-7) corresponded to the ICF qualifiers (0-4). A total of 458 rehabilitation professionals participated. The survey findings indicated a general consensus on the equivalence of FIM scores with ICF qualifiers. The median value for each item remained consistent across all item groups. Specifically, FIM 1 had a median value of 4; FIM 2 and 3 both had median values of 3; FIM 4 and 5 both had median values of 2; FIM 6 had a median value of 1; and FIM 7 had a median value of 0. Despite limitations due to the irreconcilable differences between the frameworks of existing scales and the ICF, these results underline the ICF's potential to serve as a central hub for integrating clinical data from various scales.