Gait & Posture

AimTo compare anterior and posterior standing balance reactions, as measured by single-stepping thresholds, of children with and without cerebral palsy (CP). MethodSeventeen ambulatory children with CP and 28 typically developing children, all 5-12 years of age, were recruited for this cross-sectional, observational study. Balance reaction skill was quantified as anterior and posterior single-stepping thresholds, or the treadmill-induced perturbations that consistently elicited a step in that direction. In order to understand underlying mechanisms of between-group differences in stepping thresholds, dynamic stability was quantified using the minimum margin of stability. Ankle muscle activation latency, magnitude, and co-contraction were assessed with surface electromyography. ResultsWe observed large between-group differences in anterior, but not posterior, thresholds. Between-group differences were most evident in older children, with typically developing children having larger anterior thresholds than those with CP. In response to near-threshold anterior perturbations, older typically developing children recovered from more instability than their CP peers. Older children had no between-group differences in ankle muscle activity. InterpretationThe effects of CP on balance reactions are age- and direction-specific. In response to an anterior perturbation, older typically developing children recovered from more instability than their peers with CP. What this paper addsO_LIChildren with CP have age- and direction-specific balance-reaction impairments. C_LIO_LIImpairment was most evident in the anterior reactions of older children ({approx}11 years). C_LIO_LITypically developing children recovered from more anterior instability than those with CP. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/19006585v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1d8fdf5org.highwire.dtl.DTLVardef@108fc78org.highwire.dtl.DTLVardef@f72de3org.highwire.dtl.DTLVardef@1e5c2ca_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundParkinsons disease (PD) is marked by a loss of motor automaticity, resulting in decreased control of step length during gait. Rhythmic auditory cues (metronomes or music) may enhance automaticity by adjusting cadence. Both metronomes and music may offer distinct advantages, but prior attempts at quantifying their influence on spatiotemporal aspects of gait have been confounded by altered gait speeds from overground walking. We hypothesized that when gait speed is fixed, individuals with PD would experience difficulty in modifying cadence due to the concomitant requirement to alter step length, with greater changes noted with metronomes compared to music cues. Research QuestionCan a metronome or music promote spatiotemporal adjustments when decoupled from changes in gait speed in individuals with PD? Methods21 participants with PD were instructed to time their steps to a metronome and music cues (at 85%, 100%, and 115% of overground cadence) during treadmill walking. We calculated cadence, cadence accuracy, and step length during each cue condition and an uncued control condition. We compared the various cue frequencies and auditory modalities. ResultsAt fixed gait speeds, participants were able to increase and decrease cadence in response to auditory cues. Music and metronome cues produced comparable results in cadence manipulation with greater cadence errors noted at slower intended frequencies. Nevertheless, the induced cadence changes created a concomitant alteration in step length, with music and metronomes producing comparable changes. Notably, longer step lengths were induced with both music and metronome during slow frequency cueing. SignificanceThis important change conflicts with conventional prescriptive approaches, which advocate for faster cue frequencies, if applied on a treadmill. The music and metronome cues produced comparable changes to gait, suggesting that either cue may be effective at overcoming the shortened step lengths during treadmill walking if slower frequencies are used.

1.Although the time a patient can stand on one leg is a common clinical test of balance in those prone to fall, a surprising knowledge gap is how much hip abduction muscle strength is required. This is important because hip abduction strength has been shown to be important for compensating for impairments in diabetic neuropathy, for example. As a start we tested the hypothesis that maximum hip abduction muscle endurance time at 50% effort would be longer than the time that 18 young and 17 older healthy adults can stand on one leg. First, maximum hip abduction endurance time at 50% effort as well as maximum abduction strength were measured in the gravity-free plane. Then subjects were asked to balance on their left foot for as long as they could while body segment kinematics and ground reaction data were measured. The results showed that the mean intensity of the hip abduction moment required to stand on one leg exceeded 50% of the maximum hip abduction strength for all four groups (young women and men 53% and 55%, and older women and men 94% and 72% respectively). However, unipedal stance times were not limited by hip abduction 50% effort endurance time (p = 0.9). Therefore a significant portion of the hip abduction moment required to stand on one leg must be carried by passive tissues. The underlying mechanism remains to be explained.

BackgroundMyotonic dystrophy type 1 (DM1) is a prevalent inherited muscular dystrophy in adults, affecting distal muscles such as the gastrocnemius, soleus, and tibialis anterior. This leads to significant gait deviations and reduced walking speed, impacting overall well-being and increasing fall risk. ObjectiveThis study aimed to assess how walking speed affects gait kinematics in individuals with DM1. MethodEighteen individuals with genetically confirmed DM1 (4 women, age: 41.0 [35.5; 47.8] years, mass: 76.8 [67.1; 94.6] kg, height: 166.0 [156.7; 173.3] cm) participated in this study. Each participant walked barefoot along a 13-meter walkway at comfortable and fast speeds. Subsequently, spatiotemporal parameters and joint kinematics were assessed. ResultsThe step length (p < 0.001), cycle speed (p < 0.001), and cadence (p < 0.001) increased significantly, leading to a higher walking speed. Moreover, the vertical amplitude of the center of mass (CoM) increased significantly (p = 0.015), while the mediolateral amplitude decreased (p = 0.001) at fast walking condition. In addition, significant kinematic changes included increased trunk tilt (p < 0.001), greater anterior pelvic tilt (p < 0.001), increased hip flexion at initial contact, and enhanced knee flexion during both stance and swing phases. Ankle dorsiflexion showed a trend towards increase during stance phase (p = 0.055) at fast walking condition. ConclusionsFast walking speed in individuals with DM1 lead to significant gait adaptations. These adaptations reflect compensatory mechanisms to manage muscle weakness. The present study revealed significant changes in spatiotemporal parameters related to walking speed. Fast walking also highlighted kinematic adaptations in trunk, pelvis and lower limb joints. These findings enhance our understanding of gait deviation in individuals with DM1 and suggest the potential benefits of targeted fast walking training in this population.

Cerebral palsy (CP) is characterized by neuromusculoskeletal impairments, including reduced muscle fiber lengths, which alter muscle-tendon unit (MTU) lengths and contribute to gait deviations. Estimation of MTU length reliability using musculoskeletal modeling is essential for guiding interventions such as muscle lengthening. This study aims to assess within-assessor (WA) and between-assessor (BA) reliability of MTU length estimation during gait in CP and non-impaired (NI) individuals. 38 individuals (19CP,19TD) participated in 3 3DGA sessions (2 by the same assessor). Normalized MTU length, MTU lengthening, and maximum lengthening range of the rectus femoris, semitendinosus, and gastrocnemius medialis were reported. Reliability was quantified through the standard error of measurement (SEM) and minimal detectable change (MDC). The mean SEM (MDC) during the gait ranged from 1.0-2.1% (2.5-5.7%) for normalized MTU length, from 3.6-8.7 mm (10.1-24.1 mm) for MTU lengthening, and from 2.9-8.0 mm (8.0-22.1 mm) for MTU lengthening range in individuals with CP. In NI individuals, the mean SEM (MDC) during the cycle ranged from 0.6-1.3% (1.8-3.7%) for normalized MTU length, from 2.6-5.0 mm (7.3-13.9 mm) for MTU lengthening, and from 2.7-5.0 mm (7.5-12.4 mm) for MTU lengthening range. Results suggest reliable estimations by the same assessor, supporting therapeutic decision-making and patient progress monitoring.

Three-dimensional gait analysis is widely used to support clinical decision-making in neuromuscular disorders, with the Conventional Gait Model (CGM) being the most commonly applied biomechanical model in clinical practice. Recent developments of the CGM, grouped under the open-source CGM2 framework, introduced methodological updates intended to improve robustness while preserving backward compatibility. However, the reliability of these successive CGM2 iterations has not been comprehensively evaluated, particularly in pathological gait populations. This study investigated within- and between-assessor reliability of lower-limb kinematics across three CGM2 versions (2.1, 2.2, and 2.3) in asymptomatic participants and individuals with cerebral palsy. Reliability was quantified using standard error of measurement and minimal detectable change across the gait cycle. Overall measurement error remained low and consistent across models and participant groups, with standard errors close to 2{degrees} and minimal detectable changes around 6{degrees}. Introducing kinematic fitting had minimal influence on reliability, while adding tracking markers on the thigh and shank produced a modest reduction in hip transverse rotation error. These findings indicate that methodological refinements implemented in CGM2 preserve the reliability of the original CGM while providing incremental improvements for clinically relevant parameters, supporting its use in both asymptomatic and pathological gait analysis and longitudinal clinical assessments

AimTo investigate the relationship between somatosensory deficits, specifically ankle and hip joint position sense, two-point discrimination, and vibration on the (1) responses to visual perturbations during walking and (2) response improvements to visual perturbations while receiving a sensory-centric treatment, i.e., stochastic resonance (SR) stimulation, in individuals with and without cerebral palsy (CP). MethodsTwenty-eight individuals (14 CP, 14 age-and sex-matched controls) walked in a virtual reality cave while receiving visual perturbations. We applied SR to the ankle and hip joints. Data analysis consisted of bivariate correlations, and multiple regression analysis (MRA) using all four sensory tests as predictors with the responses to visual perturbation and the improvements in the responses when SR is applied as outcomes. ResultsWe found significant and strong correlations between performance on sensory tests and the responses to visual perturbations, and improvements in the responses with SR. Only one predictor could be entered into the MRA, indicating that performance on any of the sensory tests could predict the responses to visual perturbation and the improvements with SR. InterpretationIndividuals with sensory deficits are more responsive to sensory-centric interventions. This study is an initial step in identifying potential "responders" to sensory therapies in individuals with CP.

BackgroundThree-dimensional gait analysis (3DGA) is widely used to support clinical decision-making in individuals with motor impairments. However, kinematic outputs depend strongly on the underlying biomechanical model. The open-source Conventional Gait Model II (CGM2) integrates updates to joint centre estimation (CGM2.1), inverse kinematics (CGM2.2), and cluster-based segment tracking (CGM2.3). While previous work demonstrated consistency among CGM2 variants in typically developing children, their effect in clinical populations remains unknown. This study quantified how CGM2 variants influence gait kinematics in individuals with cerebral palsy (CP). MethodsTwenty-one individuals with CP (GMFCS I-II) underwent 3DGA using a 12-camera motion capture system and a CGM2.3 marker set. Hip, knee, and ankle kinematics from 487 gait cycles were computed using pyCGM2. Differences between CGM2.1, CGM2.2, and CGM2.3 were evaluated using Mean Absolute Deviation (MAD) and the adjusted coefficient of determination (R2). ResultsOverall, small differences were observed between model variants. MAD values were typically below 5{degrees} for most joints and planes, with high correlation between curves (R2>0.7). Hip rotation showed the largest discrepancies, with maximum MAD up to 7.7{degrees} when comparing CGM2.2 and CGM2.3. Differences between CGM2.1 and CGM2.3 were greater in the transverse and frontal planes but remained within acceptable limits (<5{degrees}), except for hip rotation. ConclusionThe CGM2 variant selection has limited impact on gait kinematics in individuals with CP, and most differences fall within known repeatability error. However, transverse-plane kinematics, particularly hip rotation, should be interpreted with caution when comparing data across CGM2 variants.

PurposeGait parameters are altered and asymmetrical in individual with transtibial amputation. The purpose of this study was to evaluate and compare the effect of four different prosthetic feet on lower-limb biomechanics during gait. MethodsOne young adult with transtibial ampution performed four gait analysis sessions with four foot-ankle prosthesis (Variflex, Meridium, Echelon, Kinterra). Kinematic, kinetic parameters and gait symmetry were analyzed during different prosthesis conditions. ResultsThe type of prosthesis had little effect on amputee spatiotemporal parameters. Throughout the stance phase, an increase hip angle and a reduced knee flexion and ankle dorsiflexion were observed in the amputated leg. For kinetic parameters, a reduced propulsive force (SI=0.42-0.65), reduced knee extension moment (mainly during Echelon and Kinterra conditions, SI=0.17 and 0.32, respectively) and an increased knee abduction moment (mainly during the Variflex and Meridium, SI=5.74 and 8.93, respectively) in the amputated leg. Lower support moments were observed in the amputated leg compared to the unaffected leg, regardless of the type of prosthesis (SI=0.61-0.80). ConclusionsThe prostheses tested induced different lower-limb mechanical adaptations. If better gait symmetry between lower limbs is one of the clinical goals, an objective gait analysis could help clinicians to prescribe prosthetic feet based on quantitative measurement indicators.

Walking energy consumption is higher in people with versus without a transtibial amputation, but the underlying reasons are poorly understood. Active prostheses that restore ankle power fail to decrease walking energy consumption, suggesting that there should be other reasons than a lack of ankle power. Transtibial amputation impacts walking stability, as evidenced by the increased fall risk, and there is an energetic cost associated with stabilizing walking. It is, however, unclear how transtibial amputation affects the energetic cost of stabilizing walking. We assessed the metabolic cost of stabilizing walking against treadmill belt speed perturbations (SD=0.13 m/s) in 16 subjects with and 23 subjects without a transtibial amputation at three walking speeds between 0.6 and 1.6 m/s. We focused on sagittal plane stability, as a transtibial amputation mainly affects modulation of the ankle torque, and this ankle strategy contributes most to sagittal plane control of walking at low speeds. Perturbations induced 0.24 W/kg larger increases in energy consumption across walking speeds in subjects with than without a transtibial amputation. Whereas mean reductions in step length in response to perturbations were similar between groups, individuals with an amputation increased step length variability of their intact leg more - especially at low speeds - than individuals without an amputation. As continuous control is required for unperturbed walking, an increased metabolic cost of stabilizing walking might explain - at least partially - the higher energetic cost of walking. These insights are important when seeking to reduce the metabolic cost of walking after transtibial amputation. NEW & NOTEWORTHYThe higher metabolic cost of walking in individuals with versus without a transtibial amputation is poorly understood, hindering the design of interventions. We demonstrated that transtibial amputation considerably increases the energy consumption for stabilizing walking in the sagittal plane and increases the reliance on step length adjustments to stabilize walking. This opens up perspectives for restoring walking energetics after amputation through prostheses that support sagittal plane stability.

BackgroundPatients with nervous system and musculoskeletal diseases display gait disturbance that is a leading cause of falls. Identification of disease-specific movement hallmarks is therefore an essential first step in preventing falls. Since turning, a common daily activity, is a unique movement that requires inter-limb spatial coordination, turning may be a suitable observational target for the identification of disease-specific movement disorder. However, to date, few comprehensive systematic review regarding disease-specific alterations in turning movement is available. Research questionThis systematic review with meta-analysis summarized the level of knowledge regarding movement disorders during turning in patients with nervous system and musculoskeletal diseases. MethodsA systematic review was conducted of papers throughout 2021 in accordance with PRISMA guideline. Including criteria were (1) were published in a peer-reviewed journal, (2) were written in English, (3) included adult patients who were diagnosed with musculoskeletal or nervous system diseases, (4) had a control group of age-matched healthy adults, and (5) outcomes included turning parameters. ResultsMeta-analysis revealed a significantly larger step number, longer turn duration, and shorter step length in patients with Parkinsons disease (PD) than in controls during the 180{degrees} turn, suggesting that these biomechanical alterations may be, at least in part, movement disorders associated with PD. Notably, this review identified methodological heterogeneity for turning movement assessments, which limited the identification of disease-specific movement disorders. SignificanceThis work serves as a call to action for the establishment of a standard assessment protocol towards the identification of disease-specific turning movement disorders and effective disease screening.

AimsBalance requires the cortical control of visual, somatosensory, and vestibular inputs. The aim of this cross-sectional study was to compare the contributions of each of these systems on postural control and cortical activity using a sensory reweighting approach between participants with Parkinsons disease (PD) and controls. MethodsTen participants with PD (age: 72 {+/-} 9; 3 women; Hoehn & Yahr: 2 [1.5 - 2.50]) and 11 controls (age: 70 {+/-} 3; 4 women) completed a sensory organization test in virtual reality (VR-SOT) while cortical activity was being recorded using electroencephalography (EEG). Conditions 1 to 3 were completed on a stable platform; conditions 4 to 6 on a foam. Conditions 1 and 4 were done with eyes open; conditions 2 and 5 in a darkened VR environment; and conditions 3 and 6 in a moving VR environment. Linear mixed models were used to evaluate changes in center of pressure (COP) displacement and EEG alpha and theta/beta ratio power between the two groups across the postural control conditions. Condition 1 was used as reference in all analyses. ResultsParticipants with PD showed greater COP displacement than controls in the anteroposterior (AP) direction when relying on vestibular input (condition 5; p<0.0001). The mediolateral (ML) COP sway was greater in PD than in controls when relying on the somatosensory (condition 2; p = 0.03), visual (condition 4; p = 0.002), and vestibular (condition 5; p < 0.0001) systems. Participants with PD exhibited greater alpha power compared to controls when relying on visual input (condition 2; p = 0.003) and greater theta/beta ratio power when relying on somatosensory input (condition 4; p = 0.001). ConclusionsPD affects reweighting of postural control, exemplified by greater COP displacement and increased cortical activity. Further research is needed to establish the temporal dynamics between cortical activity and COP displacement.

Tendon loading dictates rehabilitation outcomes in Achilles tendinopathy but is difficult to track in the real world. In this study, we used instrumented insole sensors to monitor Achilles tendon load for two weeks in fifteen individuals with Achilles tendinopathy, who also completed assessments of their plantar flexor strength, dynamic function, and survey-based outcomes. We used insole data to estimate two types of cumulative Achilles tendon load: overall ([&ge;]0.3xbody weight) and high-level load ([&ge;]3xbody weight). We determined Pearson correlations between (1) overall and high-level tendon loads, (2) plantar flexor moment, power, work, (3) heel raise height, repetitions, countermovement jump height, and (4) self-reported symptoms and activity. Overall cumulative tendon load moderately correlated to isometric plantar flexor moment (r = 0.543) and weakly to isokinetic and dynamic functions (0.128-0.413). Cumulative high-level tendon load strongly correlated to heel raise height (0.687) and fast isokinetic moment (0.625), and moderately to other functional measures (0.470-0.592). Symptoms weakly correlated to overall (0.392) and moderately to high-level load (0.436). Self-reported activity weakly correlated to overall (0.297) and strongly to high-level load (0.617). Stronger associations with the high-level Achilles tendon load than the overall load suggest that clinical function assessments provide insight into the real-world performance of high-loading activities. In contrast, the disconnect between overall tendon loading and plantar flexor function may explain the variability in recovery outcomes. Self-reported activity and standard heel raises represent high-level tendon load well, yet they do not always suggest functional deficit. Sensor-monitored tendon load shows promise as a new biomarker for real-world plantar flexor function in Achilles tendinopathy.

BackgroundAccurate measurement of ankle range of motion (ROM) is essential for diagnosing and treating musculoskeletal conditions, optimizing athletic performance, and managing neurological disorders such as Parkinsons disease. This study evaluates the novel Ambulosono device, a sensor-based tool, against the traditional goniometer for assessing Ankle ROM in healthy participants. MethodsA comparative cross-sectional study was conducted on 54 healthy participants aged 15 to 24 years. Ankle ROM was measured using the goniometer, placed on the lateral malleolus, and the Ambulosono device, secured on the dorsum of the foot. Participants performed maximal dorsiflexion and plantarflexion with knees extended, and five measurements were taken per device on both feet in randomized order. Statistical analyses included descriptive statistics, Bland-Altman plots, and Intraclass Correlation Coefficients (ICCs) to assess agreement and reliability. ResultsMean goniometer ROM was 58.44{degrees} (SD=5.54) versus Ambulosonos 56.80{degrees} (SD=3.88). No significant differences emerged between devices, foot sides, or gender. Bland-Altman analysis indicated agreement without P proportional bias. Reliability was excellent (Cronbachs alpha=0.983, ICC=0.983). ConclusionThe Ambulosono device is a robust tool that offers a reliable alternative to traditional goniometry, with advantages such as real-time feedback and reduced inter-rater variability. Its potential applications extend beyond clinical and athletic settings to include neurological rehabilitation and remote patient monitoring. Further research is warranted to validate its efficacy across diverse populations and real-world scenarios.

Intact ankle proprioception is essential for the control of balance and gait. This study determined ankle position sense acuity for plantarflexion and dorsiflexion. In two separate assessments, the right ankle of 30 healthy young adults was passively rotated from neutral joint position to a 15{degrees} reference position and a smaller comparison position in either plantar- or dorsiflexion. Subsequently, participants verbally indicated which position felt more flexed. After 25 trials, a psychometric function was fitted to the respective response-stimulus size difference data for each participant and two outcome measures were derived: a Just-Noticeable-Difference (JND) threshold as a measure of systematic error and an Uncertainty Area (UA) indicating random error. Analysis showed that mean JND threshold and median UA were both significantly higher in dorsiflexion when compared to plantarflexion (p = 0.008, d = 0.52; p = 0.001, rb= 0.58). These findings indicate that ankle proprioceptive acuity is not uniform for sagittal plane ankle motion but is higher for plantarflexion. We discuss differences in plantar and dorsiflexor muscle mechanoreceptor density and central proprioceptive signal processing as possible reasons for the observed differences in acuity and highlight the importance of understanding movement-specific proprioceptive acuity for designing effective rehabilitation protocols.

BackgroundLocomotor function is often impaired in children diagnosed with cerebral palsy (CP). Improving locomotor function is a common goal of treatment. The current gold standard for assessing locomotor function in CP is the gross motor function measure (GMFM-66). The GMFM-66 requires an in-person assessment by a trained clinician. It would be useful to have a measure of function that is like the GMFM-66 but can be assessed through patient report. MethodsWe queried the clinical databases of two motion analysis centers (Gillette Childrens Specialty Healthcare and Shriners Hospital - Salt Lake City) for individuals with a diagnosis of cerebral palsy (CP) who were 18 years old or younger and had undergone instrumented clinical gait analysis that included the functional assessment questionnaire (FAQ). We computed the transformed FAQ (FAQt) as the weighted sum of the skills an individual was able to perform, where the weighting was the difficulty of the skills. We assessed concurrent and external validity of the FAQt by comparing it to the GMFM-66. ResultsThe FAQt exhibited strong concurrent and external validity. Linear regression showed that the GMFM-66 explained 54% of the variance in FAQt, and the linear fit was independent of center. The FAQt evolved with age in a manner similar to the GMFM-66, with higher functioning individuals, as measured by gross motor function classification system level, achieving higher levels of function at a higher rate and an earlier age compared to their lower functioning peers. The findings with respect to GMFM-66 did not depend on the center at which the data was acquired. ConclusionsThe FAQt demonstrates strong concurrent and external validity, making it a useful measure of locomotor function.

ObjectiveTo determine the effect of different metronome cue frequencies on spatiotemporal gait parameters when walking overground compared to walking on a treadmill in people with Parkinsons disease DesignRepeated-measures, within-subject design SettingResearch laboratory ParticipantsTwenty-one people with Parkinsons disease (Hoehn & Yahr stage 1-3) InterventionsParticipants walked overground and on a treadmill with and without metronome cues of 85%, 100%, and 115% of their baseline cadence for one minute each. Main Outcome MeasuresGait speed, step length, and cadence ResultsAn interaction effect between cue frequency and walking environment revealed that participants took longer steps during the 85% condition on the treadmill only. When walking overground, metronome cues of 85% and 115% of baseline cadence yielded decreases and increases, respectively, in both cadence and gait speed with no concomitant change in step length. ConclusionsThese data suggest that people with PD are able to alter spatiotemporal gait parameters immediately when provided the appropriate metronome cue and walking environment. We propose to target shortened step lengths by stepping to the beat of slow frequency auditory cues while walking on a treadmill, whereas the use of fast frequency cues during overground walking can facilitate faster walking speeds.

BackgroundKnee osteoarthritis (OA) causes structural joint damage. The resultant symptoms can impair the ability to recover from unexpected gait perturbations, contributing to an increased fall risk. This study compared reactive stepping responses to gait perturbations between individuals with knee OA and healthy individuals. MethodsKinematic data of 35 individuals with end-stage knee OA, and 32 healthy individuals in the same age range were obtained during perturbed walking on a treadmill at 1.0 m/s. Participants received anteroposterior (trip or slip) or mediolateral perturbations during the stance phase. Changes from baseline in margin of stability (MoS), step length, step time, and step width during the first two steps after perturbation were compared between groups using a linear regression model. Extrapolated center of mass (XCoM) excursion was descriptively analyzed. FindingsAfter all perturbation modes, XCoM trajectories overlapped between individuals with knee OA and healthy individuals. Participants predominantly responded to mediolateral perturbations by adjusting their step width, and to anteroposterior perturbations by adjusting step length and step time. None of the perturbation modes yielded between-group differences in changes in MoS and step width during the first two steps after perturbation. Small between-group differences were observed for step length (i.e. 2 cm) of the second step after trip and slip perturbation, and for step time (i.e. 0.02 s) of the second step after slip perturbations. InterpretationDespite considerable pain and damage to the knee joint, individuals with knee OA showed comparable reactive stepping responses after gait perturbations to healthy participants.

PurposeMusculoskeletal (MSK) modeling and ultrasound imaging (USI) are complementary techniques that, when combined with three-dimensional gait analysis (3DGA), provide insights into muscle and/or muscle-tendon unit (MTU) characteristics during gait. Despite their potential, a synthesis of their current use during 3DGA in populations with neuromotor impairments has not been conducted. This scoping review aimed to examine how MSK modeling and USI are used alongside 3DGA to assess muscle and MTU characteristics in populations with neuromotor impairments and evaluate the potential clinical implications of these approaches on clinical assessment and decision-making. ResultsThree databases were searched up to February 2025, yielding 50 studies (42 studies used MSK modeling, 5 used USI, and 3 employed both), including 4 pathological populations (cerebral palsy, stroke, hereditary spastic paraparesis, and idiopathic toe walking), and analyzing 11 lower-limb muscles. Both MSK modeling and USI have enabled the assessment of muscle or MTU length during gait, and detection of abnormal MTU. Only MSK modeling was used to assess MTU lengthening velocity, interventions effects, and predictors of surgical outcomes. MSK modeling appears limited by modeling assumptions and lack of real-time data, whereas USI faces constraints related to data acquisition complexity and processing challenges. ConclusionsThis review enhances understanding of neuromuscular impairments and current uses of MSK modeling and USI in clinical populations. It highlights their complementary potential with 3DGA to support personalized clinical decision-making. Future work should include broader neuromotor conditions and explore automated data analysis (e.g., deep learning for USI) to improve clinical applicability.

BackgroundInertial measurement units (IMUs) have potential to be inexpensive, portable sensors for collecting gait parameters and joint kinematics. Current validation protocols generally do not investigate IMU accuracy in measuring altered gait; therefore, they cannot assess an IMUs ability to detect pathologies. The Stridelink IMU-based gait analysis device is intended for use in detecting and monitoring gait abnormalities, thus there is a need to evaluate the devices accuracy under abnormal gait conditions. Research questionHow well do measurements from the StrideLink IMU agree with motion capture (MoCap), particularly when gait is mechanically altered to simulate pathology? MethodsTwenty-eight healthy participants (ages 18-40) were analyzed during a one-minute tread-mill walk with Vicon MoCap and StrideLink. Tests were performed under normal and mechanically induced abnormal conditions (knee brace, walking boot). Equivalence testing and correlation analysis evaluated StrideLinks accuracy against MoCap. ResultsStrideLink showed statistical equivalence (within 5%) for average cadence, stride, swing, and stance times but not double support time. Many metrics were statistically equivalent (p < .001) despite induced abnormalities. Correlation analysis showed almost perfect agreement with MoCap for stride times, cadence, and stance. However, the abnormal gait protocol revealed nuances not observed in normal gait; specifically, the device underestimated swing time by [~]10 ms in knee brace restricted limbs. SignificanceThis study utilized mechanically induced gait abnormalities to assess the robustness of IMU measurements. Results indicate StrideLink yields valid temporal gait measurements comparable to reference systems, even under conditions of significant deviation, supporting the utility of using induced abnormalities for sensor validation.