GaitNet+ARL: A Deep Learning Algorithm for Interpretable Gait Analysis of Chronic Ankle Instability.

Chronic ankle instability (CAI) is a major public health concern and adversely affects people's mobility and quality of life. Traditional assessment methods are subjective and qualitative by means of clinician observation and patient self-reporting, which may lead to inaccurate assessment and reduce the effectiveness of treatment in clinical practice. Gait analysis becomes a commonly used approach for monitoring human motion behaviors, which can be applied to specific diagnosis and assessment of CAI. However, it is still challenging to recognize the pathological gait pattern for CAI subjects. In this paper, we propose an integrated deep learning framework to solve the CAI recognition problem using kinematic data. Specifically, inspired by the biomechanics of human body system, we create a simple graph neural network (GNN), termed GaitNet, that operates on a spatial domain and exploits interactions among 3-D joint coordinates. We also develop an attention reinforcement learning (ARL) model that determines attention weights of frames on a temporal domain, which is combined with GaitNet for prediction. The effectiveness of our method is validated on the kinematic NEU-CAI dataset which is collected in our institution using a stereophotogrammetric system. According to extensive experiments, we demonstrate that the selected key phases (i.e., sequences of frames with high attentions) significantly increase the predictability of the proposed biomechanics-based GNN model to differentiate between CAI cohort and control cohort. Moreover, we show a significant prediction accuracy improvement (20%-25%) by our approach compared to state-of-the-art machine learning and deep learning methods.

Inter-joint coordination variability is associated with pain severity and joint loading in persons with knee osteoarthritis.

As the lower extremity is a linked-joint system, the contribution of movements at the hip and ankle, in addition to the knee, to gait patterns should be considered for persons with knee osteoarthritis (OA). However, the relationships of joint coordination variability to OA symptoms, particularly knee pain, and joint loading is unknown. The purpose of this study was to determine the relationship of joint coordination variability to knee pain severity and joint loading in persons with knee OA. Thirty-four participants with knee OA underwent gait analysis. Vector coding was used to assess coordination variability during the early, mid, and late stance phase. Hip-knee coupling angle variability (CAV) during midstance was associated with Knee Injury and Osteoarthritis Outcome Score (KOOS) pain (r = -0.50, p = 0.002) and Visual Analog Scale pain (r = 0.36, p = 0.04). Knee-ankle CAV during midstance was associated with KOOS pain (r = -0.34, p = 0.05). Hip-knee CAV during early and midstance were associated with knee flexion moment (KFM) impulses (r = -0.46, p = 0.01). Knee-ankle CAV during early and midstance were associated with peak KFM (r = -0.51, p < 0.01; r = -0.70, p < 0.01). Moreover, knee-ankle CAV during early, mid, and late stance phase were associated with KFM impulses (r = -0.53, p < 0.01; r = -0.70, p < 0.01; r = -0.54, p < 0.01). These findings suggest that joint coordination variability may be a factor that influences pain and knee joint loading in persons with knee OA. Statement of Clinical Significance: Movement coordination of the hip, knee, and ankle should be considered in the clinical management and future research related to knee OA.

Recurrence Quantification Analysis of Ankle Kinematics During Gait in Individuals With Chronic Ankle Instability.

Purpose: An investigation of the ankle dynamics in a motor task may generate insights into the etiology of chronic ankle instability (CAI). This study presents a novel application of recurrence quantification analysis (RQA) to examine the ankle dynamics during walking. We hypothesized that CAI is associated with changes in the ankle dynamics as assessed by measures of determinism and laminarity using RQA. Methods: We recorded and analyzed the ankle position trajectories in the frontal and sagittal planes from 12 participants with CAI and 12 healthy controls during treadmill walking. We used time-delay embedding to reconstruct the position trajectories to a phase space that represents the states of the ankle dynamics. Based on the phase space trajectory, a recurrence plot was constructed and two RQA variables, the percent determinism (%DET) and the percent laminarity (%LAM), were derived from the recurrence plot to quantify the ankle dynamics. Results: In the frontal plane, the %LAM in the CAI group was significantly lower than that in the control group (p < 0.05. effect size = 0.86). This indicated that the ankle dynamics in individuals with CAI is less likely to remain in the same state. No significant results were found in the %DET or in the sagittal plane. Conclusion: A lower frontal-plane %LAM may reflect more frequent switching between different patterns of neuromuscular control states due to the instabilities associated with CAI. With further study and development, %LAM may have the potential to become a useful biomarker for CAI.

Association Rule Mining to Examine Predictors for the Outcome of Gait Rehabilitation Programs in Stroke Survivors.

ABSTRACT: This study presents a novel application of association rule data mining to determine the predictors of the response to locomotor training and home exercise for improving gait after stroke. The study was a secondary data analysis on the Locomotor Experience Applied Post Stroke Trial dataset. The association rule analysis was applied to analyze three interventions: (1) early locomotor training, (2) late locomotor training, and (3) home exercise program. The outcome variable was whether participants poststroke had greater than median improvement in the self-selected comfortable gait speed. Three types of predictors were investigated: (1) demographics, (2) behavioral and medical history, and (3) clinical assessments at baseline. Association rules were generated when they meet two criteria determined based on the data: 10% of support and 70% of confidence. The identified rules showed that the predictors of the response were different across the three interventions, which was inconsistent with the previous report based on traditional logistic regression. However, the rules were identified with high confidence but low support, indicating that they were reliable but did not appear often in the Locomotor Experience Applied Post Stroke Trial dataset. Further investigation of these rules with a larger sample size is warranted before applying them to clinical settings.

Exploiting telerobotics for sensorimotor rehabilitation: a locomotor embodiment.

BACKGROUND: Manual treadmill training is used for rehabilitating locomotor impairments but can be physically demanding for trainers. This has been addressed by enlisting robots, but in doing so, the ability of trainers to use their experience and judgment to modulate locomotor assistance on the fly has been lost. This paper explores the feasibility of a telerobotics approach for locomotor training that allows patients to receive remote physical assistance from trainers. METHODS: In the approach, a trainer holds a small robotic manipulandum that shadows the motion of a large robotic arm magnetically attached to a locomoting patient's leg. When the trainer deflects the manipulandum, the robotic arm applies a proportional force to the patient. An initial evaluation of the telerobotic system's transparency (ability to follow the leg during unassisted locomotion) was performed with two unimpaired participants. Transparency was quantified by the magnitude of unwanted robot interaction forces. In a small six-session feasibility study, six individuals who had prior strokes telerobotically interacted with two trainers (separately), who assisted in altering a targeted gait feature: an increase in the affected leg's swing length. RESULTS: During unassisted walking, unwanted robot interaction forces averaged 3-4 N (swing-stance) for unimpaired individuals and 2-3 N for the patients who survived strokes. Transients averaging about 10 N were sometimes present at heel-strike/toe-off. For five of six patients, these forces increased with treadmill speed during stance (R2 = .99; p < 0.001) and increased with patient height during swing (R2 = .71; p = 0.073). During assisted walking, the trainers applied 3.0 ± 2.8 N (mean ± standard deviation across patients) and 14.1 ± 3.4 N of force anteriorly and upwards, respectively. The patients exhibited a 20 ± 21% increase in unassisted swing length between Days 1-6 (p = 0.058). CONCLUSIONS: The results support the feasibility of locomotor assistance with a telerobotics approach. Simultaneous measurement of trainer manipulative actions, patient motor responses, and the forces associated with these interactions may prove useful for testing sensorimotor rehabilitation hypotheses. Further research with clinicians as operators and randomized controlled trials are needed before conclusions regarding efficacy can be made.

Use of thrust joint manipulation by student physical therapists in the United States during clinical education experiences.

Introduction: Thrust joint manipulation (TJM) is used in physical therapy practice and taught in entry-level curricula in the United States (US); however, research regarding implementation by student physical therapists (SPT)s is scarce. Objectives: To explore the use of TJM in SPT clinical education and factors influencing implementation. Methods: In a cross-sectional exploratory study, accredited physical therapy (PT) programs in the US (n = 227) were invited to participate in an electronic survey. SPTs were queried about TJM use and their clinical instructor's (CI) credentials during their final musculoskeletal clinical experience. Results: Forty-five programs participated in the study, consisting of 2,147 SPTs. Of those, 414 (19.3%) responses were used for analysis and 69% reported using TJM. SPTs who utilized TJM were more likely to have a CI who used TJM (p < 0.001) and/or had advanced certification/training in manual therapy (p < .001). A majority of students agreed or strongly agreed that their academic preparation provided them with clinical reasoning tools (84%) and psychomotor skills (69%) necessary to perform TJM. SPT use of TJM was facilitated by CI clinical practice, SPT competence in psychomotor skill, confidence in clinical reasoning, and practice setting. A main barrier to student use of TJM was CI lack of TJM use. Conclusions: Clinical practice of the CI appears to be a key factor in determining student use of TJM. Level of evidence: 2b.

Visuomotor control of ankle joint using position vs. force.

Ankle joint plays a critical role in daily activities involving interactions with environment using force and position control. Neuromechanical dysfunctions (e.g., due to stroke or brain injury), therefore, have a major impact on individuals' quality of life. The effective design of neuro-rehabilitation protocols for robotic rehabilitation platforms relies on understanding the control characteristics of the ankle joint in interaction with external environment using force and position, as the findings in upper limb may not be generalizable to the lower limb. This study aimed to characterize the skilled performance of ankle joint in visuomotor position and force control. A two-degree-of-freedom (DOF) robotic footplate was used to measure individuals' force and position. Healthy individuals (n = 27) used ankle force or position for point-to-point and tracking control tasks in 1-DOF and 2-DOF virtual game environments. Subjects' performance was quantified as a function of accuracy and completion time. In contrast to comparable performance in 1-DOF control tasks, the performance in 2-DOF tasks was different and had characteristic patterns in the position and force conditions, with a significantly better performance for position. Subjective questionnaires on the perceived difficulty matched the objective experimental results, suggesting that the poor performance in force control was not due to experimental set-up or fatigue but can be attributed to the different levels of challenge needed in neural control. It is inferred that in visuomotor coordination, the neuromuscular specialization of ankle provides better control over position rather than force. These findings can inform the design of neuro-rehabilitation platforms, selection of effective tasks and therapeutic protocols.

Between-side differences in hand-grip strength across the age span: Findings from 2011-2014 NHANES and 2011 NIH Toolbox studies.

This project was undertaken to describe percentage differences in the grip strength between the dominant and nondominant-sides of left- and right-handed males and females across the age span. Data used in the project were from population-based samples of participants: 13,653 from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) and 3,571 from the 2011 normative phase of the National Institutes of Health (NIH) Toolbox project. Depending on how percentage differences were calculated, the overall grip strength was a mean 5.0-5.6% greater on the dominant than nondominant side. The percentage differences were significantly greater for individuals who were right-hand dominant rather than left-hand dominant. The differences also varied according to gender. We present summary data for percentage differences stratified by study, handedness, and gender. The values can be used to determine whether grip strength on one side is limited relative to the other.

Handgrip Strength: A Comparison of Values Obtained From the NHANES and NIH Toolbox Studies.

IMPORTANCE: Handgrip dynamometry is probably the most commonly used method to characterize overall human muscle strength. OBJECTIVE: To compare and summarize grip strength measurements obtained from two population-based studies. DESIGN: Secondary data analysis. SETTING AND PARTICIPANTS: Data from (1) the 2011-2014 National Health and Nutrition Examination Survey (NHANES) with 13,918 participants and (2) the 2011 normative phase of the National Institutes of Health (NIH) Toolbox project with 3,594 participants. OUTCOMES AND MEASURES: The NHANES values used were the mean and best of three trials; the NIH Toolbox value used was the one maximum trial after a practice trial. RESULTS: General linear model analysis revealed that values obtained from the NIH Toolbox differed from NHANES best values but not from NHANES mean values. The analysis also indicated, regardless of the values used, that grip strength differed significantly between dominant and nondominant sides, males and females, and age groups. We provide updated reference values for handgrip strength. CONCLUSIONS AND RELEVANCE: On the basis of these analyses, we summarize grip strength measures obtained from the NHANES and NIH Toolbox for side, gender, and age group strata. Reference values are essential to assist in the interpretation of testing results and clinical decision making.

An examination of muscle force control in individuals with a functionally unstable ankle.

Previous studies suggest that functional ankle instability (FAI) may be associated with deficits in the ability to sense muscle forces. We tested individuals with FAI to determine if they have reduced ability to control ankle muscle forces, which is a function of force sense. Our test was performed isometrically to minimize the involvement of joint position sense and kinesthesia. A FAI group and a control group were recruited to perform an ankle force control task using a platform-based ankle robot. They were asked to move a cursor to hit 24 targets as accurately and as fast as possible in a virtual maze. The cursor movement was based on the direction and magnitude of the forces applied to the robot. Participants underwent three conditions: pre-test (baseline), practice (skill acquisition), and post-test (post skill acquisition). The force control ability was quantified based on the accuracy performance during the task. The accuracy performance was negatively associated with the collision count of the cursor with the maze wall. The FAI group showed reduced ability to control ankle muscle forces compared to the control group in the pre-test condition, but the difference became non-significant in the post-test condition after practice. The change in performance before and after practice may be due to different degrees of reliance on force sense.

Global rating of change: perspectives of patients with lumbar impairments and of their physical therapists.

Background: Global rating of change (GROC) scores provide a means of measuring patients' self-perceived change in health status over time. Objectives: The purposes of the study were to examine agreement of GROC ratings between the patient (GROCp) and the treating therapist (GROCt), the impact on the minimal clinically important difference (MCID) estimates by reporting resources, and the relationships between the subjective GROC scores and objective outcome measures. Methods: Data from 52,767 patients with orthopedic lumbar spine impairments treated in 623 outpatient rehabilitation clinics in 34 states (United States) were analyzed. Patient's functional status (FS) before and after the treatment was measured using the Lumbar Computerized Adaptive Testing (LCAT) survey (0-100 scale). The GROC ratings were obtained from both the patients and their caring therapists at discharge. Results: On average, GROCp (mean [(SD] = 3.1 [4.1]) was 1.9 points lower than GROCt (mean [SD] = 5.0 [1.9]). There were negligible differences between MCID estimates derived from the patients' GROC ratings (MCID cutoff = 9.2) and from the therapists' GROC ratings (MCID cutoff = 9.5). While only analyzing patient data whose GROCp ≥ 0, the intraclass correlation coefficient between GROCp and GROCt was 0.61, the GROCp correlated with FS at intake at r = 0.12, with FS at discharge at r = 0.56, and with FS change scores at r = 0.47. Conclusions: Therapists tended to report higher GROC ratings than their patients did but there were negligible differences between MCID estimates derived from GROCp and that derived from GROCt.

Summary of grip strength measurements obtained in the 2011-2012 and 2013-2014 National Health and Nutrition Examination Surveys.

STUDY DESIGN: Cross-sectional and descriptive study. INTRODUCTION: Supported by the Centers for Disease Control and Prevention, the National Health and Nutrition Examination Survey (NHANES) began collecting grip strength data from nationally representative samples in 2011. PURPOSE OF THE STUDY: To examine the stability of the grip strength values across 2 data release cycles and provide updated US population-based grip strength values for 6 to 80 year olds. METHODS: Handgrip data from 13,676 participants aged 6-80 years were extracted from the NHANES 2011-2014 database. The muscle strength/grip test component measured the isometric grip strength using a Takei digital handgrip dynamometer (Takei Scientific Instruments, Shinagawa-Ku, Tokyo). Grip strength values (best of 3 trials for each hand) were summarized by gender, dominant side, and age group. Grip data from 2 data release cycles (2011-2012 vs 2013-2014) were compared. RESULTS: Differences between 2 data release cycles were negligible. Hence, we summarize grip strength values across the entire 2011-2014 period. The mean grip strength ranged from 50.3 kg for the dominant hand of 30- to 34-year-old men to 10.0 kg for the nondominant hand of 6-year-old girls. DISCUSSION: The summary data we present provide relatively current reference values to which tested individuals can be compared. However, clinicians and/or researchers should be aware that the instrumentation and procedures may influence the values. CONCLUSIONS: Results supported the stability of the NHANES grip strength values across data release cycles.

Effects of kinesiotaping and athletic taping on ankle kinematics during walking in individuals with chronic ankle instability: A pilot study.

BACKGROUND: Individuals with chronic ankle instability (CAI) tend to walk with an overly inverted foot, which increases the risk of ankle sprains during stance phase. Clinicians could perform ankle taping using kinesiotape (KT) or athletic tape (AT) to address this issue. Because KT is elastic while AT is not, the techniques and underlying mechanisms for applying these tapes are different, which may lead to different outcomes. RESEARCH QUESTION: To compare the effects of KT and AT interventions on foot motion in the frontal plane and tibial motion in the transverse plane during stance phase of walking. METHODS: Twenty subjects with CAI were assigned to either KT or AT group, and walked on a treadmill in no tape and taped conditions. Their foot and tibial motions were captured by 3D motion analysis system. The main component of KT application was two pieces of tape applied from the medial aspect of the hindfoot to the lateral to generate a pulling tension towards eversion. AT was applied to the ankle using the closed basket weave approach. AT was not stretchable and not able to generate the same pulling tension as KT. RESULTS: KT increased foot eversion during early stance, but showed no effect during late stance. AT increased tibial internal rotation during late stance, but showed no effect during early stance. SIGNIFICANCE: Compared to AT, KT better provides a flexible pulling force that facilitates foot eversion during early stance, while not restricting normal inversion in late stance during walking. KT may be a useful clinical tool in correcting aberrant motion while not limiting natural movement in sports.

Muscle activation pattern during self-propelled treadmill walking.

[Purpose] To examine muscular demands during self-propelled treadmill walking to provide a potential option for fitness training. [Participants and Methods] Eleven healthy college students were recruited. Participants walked under three conditions: over-ground walking at a self-selected speed, treadmill walking at a self-selected speed, and treadmill walking at a speed comparable to that of over-ground walking. Step lengths and lower extremity muscle activations were recorded while participants walked under the three conditions. [Results] Step lengths were significantly shorter when participants walked on a self-propelled treadmill than when walking over-ground. The spatiotemporal and muscle activations of the gaits varied among the different walking conditions. Muscular demands at the moment of heel-strike were higher around the hip and knee when walking on the self-propelled treadmill than when walking over-ground. [Conclusion] During heel-strike, the lower extremity extensors were activated more on the self-propelled treadmill with an incline, especially at faster speeds, than during over-ground walking. A low-cost, self-propelled treadmill may be a modality for training specific muscles.

Rasch Analysis of the Activities-Specific Balance Confidence Scale in Older Adults Seeking Outpatient Rehabilitation Services.

Background The Activities-specific Balance Confidence (ABC) scale measures confidence in performing various ambulatory activities without falling or experiencing a sense of unsteadiness. Objectives This study (1) examined the ABC scale (0-100) using Rasch analysis, (2) assessed statistically reliable change, and (3) developed a functional staging to guide clinical interpretation of a patient's improvement. Methods The authors examined rating-scale structure, item difficulty hierarchy, item fit, person-item match, separation index, differential item functioning, test precision, and unidimensionality. Additionally, this cross-sectional study of 5012 older patients seeking outpatient rehabilitation therapy in 123 clinics estimated the minimal detectable change and developed a functional staging. Results The item "walk outside on icy sidewalks" was the most difficult item, while the item "reach for a small can off a shelf at eye level" was the easiest item. Overall, average patient ability estimates of 56.2 ± 20.3 were slightly higher than the average item difficulty estimates of 45.9 ± 7.8. With a separation index equal to 3.65, the ABC scale items can differentiate individuals into 5.2 statistically distinct strata. Most ABC scale items were free of differential item functioning. For example, "walk outside on icy sidewalks" was easier for patients who were underweight. Results supported unidimensionality of the ABC scale, with the first factor explaining 77% of the total variance. The estimated minimal detectable change was 15 points. The authors provided an example of functional staging application. Conclusion Results supported sound psychometric properties and clinical usage of the ABC scale for older adults seeking outpatient rehabilitation therapy. J Orthop Sports Phys Ther 2018;48(7):574-583. Epub 30 Mar 2018. doi:10.2519/jospt.2018.8023.

Assessing manual dexterity: Comparing the WorkAbility Rate of Manipulation Test with the Minnesota Manual Dexterity Test.

STUDY DESIGN: Cross-sectional study. INTRODUCTION: The WorkAbility Rate of Manipulation Test (WRMT), an adaptation of the Minnesota Manual Dexterity Test (MMDT), contains a revised board and protocols to improve its utility for therapy or fitness assessment. PURPOSE OF THE STUDY: To describe the development and preliminary psychometric properties of WRMT. METHODS: Sixty-six healthy participants completed MMDT and WRMT in a random order followed by a user experience survey. We compared tests using repeated-measures analysis of variance, test-retest reliability, and examined agreement between tests. RESULTS: Despite the similarities of these 2 instruments, the different administration protocols resulted in statistically different score distributions (P < .001). Results supported good test-retest reliability of WRMT (placing test ICC = 0.88-0.90 and turning test ICC = 0.68-0.82). The WRMT correlated moderately with MMDT (r = 0.81 in placing test and r = 0.44-0.57 in turning test). Bland-Altman plot showed that the differences in completion time were 3.8 seconds between placing tests and 19.6 (both hands), 0.3 (right hand), and 3.9 (left hand) seconds between turning tests. Overall, participants felt that the instruction of WRMT was easier to follow (44%) and preferred its setup, color, and depth of the test board (49%). Time required to complete 1 panel of 20 disks correlated highly with the time needed to finish a complete trial of 60 disks in both MMDT (r = 0.91-0.97) and WRMT (r = 0.88-0.95). CONCLUSIONS: Caution is warranted in comparing scores from these 2 test variants. LEVEL OF EVIDENCE: 3b.

An examination of lower limb asymmetry in ankle isometric force control.

While asymmetries have been observed between the dominant and non-dominant legs, it is unclear whether they have different abilities in isometric force control (IFC). The purpose of this study was to compare ankle IFC between the legs. IFC is important for stabilization rather than object manipulation, and people typically use their non-dominant leg for stabilization tasks. Additionally, studies suggested that a limb can better acquire a motor task when the control mechanism of the task is related to what the limb is specialized for. We hypothesized that the non-dominant leg would better (1) control ankle IFC with speed and accuracy, and (2) acquire an ankle IFC skill through direct learning and transfer of learning. Two participant groups practiced an IFC task using either their dominant or non-dominant ankle. In a virtual environment, subjects moved a cursor to hit 24 targets in a maze by adjusting the direction and magnitude of ankle isometric force with speed (measured by the time required to hit all targets or movement time) and accuracy (number of collisions to a maze wall). Both groups demonstrated similar movement time and accuracy between the dominant and non-dominant limbs before practicing the task. After practice, both groups showed improvement in both variables on both the practiced and non-practiced sides (p < .01), but no between-group difference was detected in the degree of improvement on each side. The ability to control and acquire the IFC skill was similar between the legs, which did not support the brain is lateralized for ankle IFC.

Hip-ankle coordination during gait in individuals with chronic ankle instability.

Individuals with chronic ankle instability (CAI) may have sensorimotor impairments that affect control at the hip in addition to the ankle. The purpose of this study was to compare hip-ankle coordination and coordination variability between individuals with CAI and healthy individuals during walking. Ten healthy subjects and 10 subjects with CAI were recruited to walk on a treadmill. Hip-ankle coordination was quantified using vector coding, and coordination variability was quantified using coefficient of correspondence. We found significant between-group differences in hip-ankle coordination in the frontal plane around loading response (Control: 165.9±18.4°; CAI: 127.6±48.6°, p=0.04) and in the sagittal plane around the first half of mid stance (Control: 307.2±9.8°; CAI: 291.8±11.4°, p<0.01), terminal stance (Control: 301.1±13°; CAI: 313.4±10.9°, p=0.04), and pre-swing (Control: 243.9±35.2°; CAI: 329.9±57.8°, p<0.01). We also found significant between-group differences in hip-ankle coordination variability in the frontal plane around the second half of mid stance (Control: 0.54±0.06; CAI: 0.45±0.07, P<0.01). CAI is associated with alteration of hip-ankle coordination and coordination variability in stance phase during walking. Gait training is important in CAI rehabilitation, and the training should address altered hip-ankle coordination to reduce the risk of recurrent injuries.

Feedback and Feedforward Control During Walking in Individuals With Chronic Ankle Instability.

Study Design Controlled laboratory study. Background Recurrent ankle sprains associated with chronic ankle instability (CAI) occur not only in challenging sports but also in daily walking. Understanding whether and how CAI alters feedback and feedforward controls during walking may be important for developing interventions for CAI prevention or treatment. Objective To understand whether CAI is associated with changes in feedback and feedforward control when individuals with CAI are subjected to experimental perturbation during walking. Methods Twelve subjects with CAI and 12 control subjects walked on a treadmill while adapting to external loading that generated inversion perturbation at the ankle joint. Ankle kinematics around heel contact during and after the adaptation were compared between the 2 groups. Results Both healthy and CAI groups showed an increase in eversion around heel contact in early adaptation to the external loading. However, the CAI group adapted back toward the baseline, while the healthy controls showed further increase in eversion in late adaptation. When the external loading was removed in the postadaptation period, healthy controls showed an aftereffect consisting of an increase in eversion around heel contact, but the CAI group showed no aftereffect. Conclusion The results provide preliminary evidence that CAI may alter individuals' feedback and feedforward control during walking. J Orthop Sports Phys Ther 2016;46(9):775-783. Epub 5 Aug 2016. doi:10.2519/jospt.2016.6403.

Repeat Exposure to Leg Swing Perturbations During Treadmill Training Induces Long-Term Retention of Increased Step Length in Human SCI: A Pilot Randomized Controlled Study.

OBJECTIVE: To determine whether repeat exposure to force perturbations during treadmill training can induce long-term retention of improved step length and overall improvements in locomotor function in persons with spinal cord injury. DESIGN: Fourteen patients with spinal cord injury were recruited and randomly assigned to swing resistance or swing assistance training groups. A controlled swing resistance or assistance force, for resistance or assistance training groups, respectively, was applied to both legs through a cable-driven robotic system during treadmill training. Each participant trained 3 times per week for 6 weeks. Step length, walking speed, 6-minute walking distance, and other clinical assessments were evaluated before and after 6 weeks of training and 8 weeks after the end of training. RESULTS: A significant increase in step length was observed after 6 weeks of resistance training (P = 0.04). Step length tended to increase after assistance treadmill training, but the change was not significant (P = 0.18). The changes in step length and functional gains had no significant difference between 2 groups. CONCLUSIONS: Repeat exposure to swing resistance during treadmill training may induce a prolonged retention of increased step length, although it remains unclear whether swing resistance versus assistance is more effective in inducing increased step length.