Gait & Posture

Purpose: Treadmills (TM) are widely used for gait assessment in older adults (OA), yet their ecological validity across inclined terrain remains underexplored. This study compared spatiotemporal, physiological, and kinetic gait outcomes between TM and overground (OG) walking across flat, uphill, and downhill terrain in OA and younger adults (YA), and examined sensorimotor predictors of speed discrepancies. Methods: Twenty-six OA (70{+/-}6 years; 22 women) and 24 YA (26{+/-}5 years; 7 women), none with prior TM experience, completed matched TM and OG trials across three terrain conditions. Self-selected TM speed was determined using a bidirectional protocol. The modified Clinical Test of Sensory Interaction in Balance quantified sensorimotor profiles. Mixed-design ANCOVAs and multiple regression examined condition, inclination, and group effects with sex as a covariate. Results: TM speeds were consistently slower than OG across all conditions in both groups ({Delta} = -0.35 m/s, d = -1.67), with shorter stride length, lower cadence, and altered support phase timing; YA showed larger reductions and a greater shift toward double support than OA. Foot clearance at midswing was largely preserved across modalities. TM walking elicited higher heart rate and RPE despite slower speeds, most pronounced in OA uphill. Ground reaction forces and loading rates were substantially reduced on the TM. Sensorimotor profiles predicted the downhill speed discrepancy (R2 = 0.49), with vestibular and somatosensory contributions as independent predictors alongside age group. Conclusion: TM-derived speed, spatiotemporal, and physiological measures are not interchangeable with real-world ambulation data in OA across inclined terrain.

Impaired gait performance and stability is a key symptom often defining disease outcome in people with Multiple Sclerosis. Step-by-step foot placement control in response to variations in the center-of-mass kinematic state is a crucial gait stability mechanism, especially in the mediolateral direction. Even though it is known that people with Multiple Sclerosis are at an increased risk of falling, step-by-step foot placement control remains to be characterized in this population. Here, we explored characteristic foot placement control in ten people with early stage Multiple Sclerosis, compared to 21 controls walking at a similar average gait speed, during 1-minute steady-state treadmill walking. Kinematic data were analyzed using a linear feedback model that correlated foot placement with the center-of-mass kinematic state during the preceding swing phase. People with Multiple Sclerosis demonstrated step-by-step foot placement control in both the mediolateral and anteroposterior directions. No differences were found in foot placement precision between groups. However, foot placement responses to variations in center-of-mass velocity proved stronger in people with Multiple Sclerosis. Moreover, the contribution of mediolateral center-of-mass velocity feedback to the control mechanism was higher in people with Multiple Sclerosis as compared to neurologically healthy controls. Our results suggest that foot placement control is still retained in early clinically evident stages of Multiple Sclerosis, but is realized through differently weighted sensory feedback control.

Impaired motor control post-stroke results in reduced walking speeds and increased gait variability. This variability reduces reliability and makes identifying longitudinal changes via gait analysis difficult since changes may occur within the margin of measurement error. We quantified intra-class correlation coefficients (ICC) and minimal detectable change (MDC) in post-stroke individuals and neurotypical individuals walking at matched speeds, to isolate the impact of gait speed and post-stroke impairments on gait-analysis reliability. We collected gait data over two days from N=15 post-stroke individuals walking on a treadmill at their self-selected speed, and from N=13 age- and sex-matched neurotypical controls walking at both their self-selected speed and a speed matched to a post-stroke participant. We calculated ICC and MDC values for spatiotemporal variables, bilateral joint ranges of motion (ROM), and bilateral peak propulsive and peak vertical ground reaction forces (GRF). Spatiotemporal ICCs showed excellent reliability across groups (range [0.813-0.988]), yet MDC values were greater post-stroke than in speed-matched controls. ICCs for joint ROM ranged from poor to excellent reliability across groups ([0.362-0.960]). Post-stroke joint ROM MDCs were 27%-53% of the gait ROM compared to 11%-42% in neurotypical controls. ROM MDCs were greater in the non-paretic compared to the paretic extremity. ICC for peak GRFs showed good to excellent reliability across groups (range [0.778-0.980]), with post-stroke peak GRF MDCs greater than in speed-matched controls. Our results suggest that stroke related neuromotor impairments influence reliability beyond the effects of walking speed alone, and we provide quantitative MDC benchmarks for interpreting gait changes post stroke following clinical interventions.

Static force plates (FP) are the gold standard for measuring ground reaction forces (GRF) and computing joint moments through inverse dynamics in gait analysis. However, they are restricted to controlled environments, and the number of steps analyzed is limited by the plates embedded in the floor. To address these limitations, portable solutions such as sensorized insoles, socks, or shoes have emerged. Yet, creating wearable systems capable of measuring three-dimensional GRF in real-world conditions remains challenging. Current sensorized shoes often incorporate thick sensors (up to 2 cm), reducing usability and limiting their application in pathological populations or dynamic tasks like running. This study evaluates the usability of ShokacShoes, a novel sensorized shoe integrating three thin, three-dimensional force sensors, and explores its potential as a Wearable Force Plate (WFP). Eight healthy participants performed slow, natural, and fast walking using two insole configurations. Force and temporal metrics were derived from WFP and FP data. Results indicate that WFP enables accurate step segmentation and detects significant effects of speed and insole type on temporal and force metrics, confirming its reliability under different walking conditions. Comparisons with FP revealed differences in force metrics and signal morphology, though temporal parameters remained consistent. These results are likely due to sensor quantity and positioning. Thereby, ShokacShoes represent a valid solution capable of measuring three-dimensional forces within commercial footwear. Future work will focus on validating the applicability of a new version of ShokacShoes against gold-standard FP in a comprehensive validation study involving diverse real-world scenarios and pathological conditions.

Age-related decline in postural control is an important factor that increases the fall risk of older adults. Fingertip vibrotactile stimulation has been developed to provide light touch-like somatosensory input. However, evidence regarding differences among older age groups is limited. This study examined the effects of fingertip vibrotactile stimulation on postural control in 348 community-dwelling older adults classified as young-old (age 65-74 years), old-old (age 75-84 years), and oldest-old (age 85 years or older). Participants stood with eyes closed and feet together under stimulation and no stimulation conditions. The center of pressure (COP) velocity and COP area were measured using a force plate. The natural log-transformed COP area was used for the analysis. Linear mixed models were used to examine the effects of age group, stimulation conditions, and measurement segments. The COP velocity under the stimulation condition was significantly lower than that under the no stimulation condition; however, the COP area did not change significantly. Significant main effects of age group were observed for both COP indices, but no interaction between age group and stimulation condition was observed. Fingertip vibrotactile stimulation may reduce the COP velocity across older age groups, thus reflecting the effects on postural adjustment frequency.

Objective: To investigate the clinical validity of finger-worn accelerometers for providing a comprehensive assessment of upper-limb motor performance in stroke survivors in real-world environments, compared to wrist-worn accelerometers, and to examine how the clinimetric properties of wearable-based motor performance measures vary with the duration of patient data collection. Design: Cross-sectional observational design. Setting: Research laboratory and free-living environments. Participants: Twenty-seven stroke survivors aged 18-80 years with ischemic or hemorrhagic stroke at least six months prior to enrollment and mild-to-moderate upper-limb impairment without severe range-of-motion restrictions were enrolled. Three participants were ineligible and four withdrew, resulting in a final cohort of 20 participants (N = 20). Interventions: Not applicable. Main Outcome Measures: Wearable-based motor performance measures derived from fine-hand movements, gross-arm movements, and the combination of fine-hand and gross-arm movements captured by finger-worn and wrist-worn accelerometers in naturalistic settings for 6.4 {+/-} 1.8 days. Results: Wearable-based motor performance measures from fine-hand movements demonstrated the strongest convergent validity, known-group validity, and test-retest reliability, followed by those from combined and gross-arm movements. Convergent validity and test-retest reliability of wearable-based motor performance measures improved with longer monitoring durations, with four days being sufficient to obtain accurate and reliable upper-limb measures. Conclusions: Wearable-based motor performance measures from finger-worn accelerometers provide a more comprehensive assessment of upper-limb motor performance than those from wrist-worn accelerometers, supporting their use for real-world monitoring in stroke survivors. Furthermore, the improvements in clinimetric properties of wearable-based motor performance measures with longer monitoring durations highlight the importance of multi-day monitoring to mitigate day-to-day variability and ensure robust assessment.

Importance: There are very few interventions designed for individuals with the most severe mobility impairments. Robotic walking may be an effective way to facilitate exercise in this population. Objective: To examine how robot-assisted walkers physical parameters and user characteristics moderate the exercise intensity achieved by individuals with neuromotor disorders causing mobility impairments. Design: A prospective study. Intervention: A single-session intervention involving an overground robot-assisted walker that can be used in an endurance mode requiring no voluntary movement or a strength mode during which voluntary movement could impact the gait pattern. Participants: Individuals with pediatric-onset mobility impairments Main Outcome Measures: Participants were characterized based on their age, sex, diagnosis, and Gilette Functional Assessment Questionnaire (FAQ) levels. Heart rate during the final minute of four 5-minute walking conditions: strength mode at fast speed, strength mode at slow speed, endurance mode at fast speed and endurance mode at slow speed was expressed as a percentage of each participant heart rate reserve (%HRR). Linear mixed-effects models were used to evaluate the impact of speed, device mode and user characteristics on the level of exercise achieved. Results: 29 individuals (aged 2-26 years) with mobility impairments (FAQ levels 1-6) completed this study. Fast speeds were associated with a higher %HRR (beta= 2.11, SE = 1.03, p = 0.044). Participants in FAQ class 1 exhibited significantly higher %HRR compared with those in FAQ classes 2 and 3 (beta=18.6, SE=7.31, p=0.017; beta= 16.9, SE = 8.13, p = 0.047, respectively). No other device or participant characteristics were associated with exercise intensity. Conclusions: To facilitate higher exercise levels, users of robot-assisted walkers can increase their speed. Individuals who cannot take steps due to their neuromotor impairments experience the highest levels of exercise. Relevance: The findings in this study highlight the promise of robot-assisted walkers to improve health, particularly in those who often face the greatest barriers to exercise.

Background: Prolonging ambulation is an important treatment goal in children with Duchenne muscular dystrophy (DMD). Clinical management targets 'actionable' (i.e., modifiable) impairments, such as progressive muscle weakness and contractures, that underlie gait pathology. Gait classification may improve clinical decision-making, but the utility of gait classification in clinical practice depends on understanding how underlying, actionable impairments contribute to distinct gait patterns, which remains insufficiently understood. The research questions were: (1) Can DMD gait patterns be accurately classified from actionable impairments? and (2) Can the model's predictions be explained, and do these explanations provide clinical utility and increase trust in the model? Methods: A retrospective dataset of 274 lower-limb observations from 137 assessments in 30 boys with DMD was analyzed, including 3D gait analysis, instrumented strength assessment, and clinical examination (manual muscle testing, goniometry and clinical stiffness scale). Observations were classified into the mildly affected, tiptoeing, or flexion gait pattern. Ten predictors representing actionable impairments were included: nine predictors related to muscle weakness and contractures, and body mass index (BMI). A balanced random forest classifier was evaluated with leave-one-group-out cross-validation. Model interpretability was explored using SHapley Additive exPlanations to generate global and local explanations. An interview with a clinical expert assessed the utility of the explanations as the primary outcome, with trust in and expectations of both the model and the explanations as secondary outcomes. Results: The model achieved an accuracy of 74.5%. Global explanations identified hip and knee weakness, gastrocnemius-soleus contractures, and BMI as the most important predictors across gait patterns. Local explanations illustrated how patient-specific impairments informed individual predictions. The user study demonstrated the clinical utility of the explanations, as they were perceived as interpretable, provided useful insights, and these insights were actionable. The explanations largely aligned with the expectations and increased self-reported trust in the model. Conclusions: Gait patterns in DMD can be predicted from clinically actionable impairments, and explainable artificial intelligence can translate model outputs into meaningful clinical insights. This approach is promising for supporting both general and personalized rehabilitation and orthopedic strategies aimed at prolonging ambulation in DMD. Further validation in larger, multi-center cohorts is needed.

Purpose: To explore how 12-weeks of robotic walking impacts physical function and sequelae of inactivity for individuals with pediatric-onset neuromotor impairments. Methods: A single-arm mixed-methods interventional study examined robotic walking for 12-weeks in home and community settings, with 12-week follow-up. Outcomes included family goals (Goal Attainment Scale (GAS)) and perspectives (Interviews), postural control (Early Clinical Assessment of Balance), physical activity (Actigraphy, Habitual Activity Estimation Scale, Patient Reported Outcome Measurement Information System (PROMIS) Physical Activity) and sequelae of inactivity (PROMIS Sleep Disturbances, Bowel Function Diary). GAS was collected pre-training, post-training, and 12-week follow-up. All other quantitative outcomes were collected every 4-weeks. Quantitative data are described with median (25th-75thpercentile) and analyzed using a Skillings-Mack test with post-hoc Wilcoxon Signed-Rank. Qualitative interviews were conducted before and after training and analyzed thematically. Results: 15 participants aged 4-23 completed this study. Participants had cerebral palsy (10/15) or rare genetic conditions (5/15), and most used a wheelchair in community settings. Postural control improved (test-statistic = 23.0, p<0.001) after 8 weeks (change=5.0(0.0-21.4), p=0.016) and was maintained through 12-week follow-up (change=13.7(3.1-23.7), p=0.008). Over half of the participants achieved goals (t-score > 50) after training. Exploratory analyses suggest improvements in sleep disturbance immediately after training (p=0.025) and 4-weeks after (p=0.047). All measures of physical activity did not improve. Parents reported improvements in walking, activities of daily living, and sequelae of inactivity (i.e., bowel function, appetite, and sleep). Conclusions: Improvements were seen across a range of measures and notably postural control improvements were maintained at the follow-up. Parents perceived improvements in physical function and activities of daily living. Future research is warranted to further understand the impacts of robotic walking for children and small adults with mobility impairments.

[Purpose] By pairing repeated peripheral muscle fatigue induction with a functional and ADL-based assessment, this study tests whether hand muscle fatigue alone is sufficient to im pair fine motor performance in healthy adults performing ADL-inspired tasks. [Participants and Methods] Thirty healthy male and female university students performed 11 tasks twice, once in the pre-fatigue condition and once in the post-fatigue condition. The performance of each task was graded on a 0-4 scale. The score and the time to finish the task (TTFT) were recorded twice, for both the pre- and post-fatigue phases. Maximum force gen eration (MFG) of each participant's grip was recorded prior to the tasks in the pre-fatigue phase and again in the fatigue condition after performing the fatigue protocol. [Results] Muscle fatigue did not have a significant effect on the fine motor performance of the thirty participants, neither (TTFT) nor the scores of each task (p > 0.05) (r=0.08). In contrast, hand muscle fatigue led to a significant decrease in the mean (MFG) for both males and females (p<0.01). [Conclusion] Hand muscle fatigue led to a significant decrease in the mean grip MFG for both sexes. However, this reduction did not translate into impaired fine motor performance during ADL-like tasks. Consequently, under muscle fatigue, hand grip changes during fine tasks tested are rare and have minor to no impact on hand performance. This study suggests that acute peripheral muscle fatigue can coexist with preserved fine motor performance in healthy populations.

Proprioception can be assessed in several ways, including movement detection, joint position matching, and matching across sensory frames of reference. These task types make different demands, yet they are rarely compared within the same participants on the same device, and psychometric data for wrist-focused batteries are limited. This work had two aims: to compare performance across different levels of proprioceptive judgment, and to establish the within-day test-retest reliability of each. We evaluated three robotic wrist tasks spanning judgments within a single reference frame and across reference frames: joint detection threshold (JDT), same-frame joint-to-joint matching (J-to-J), and cross-frame joint-to-visual matching (J-to-V). Methods. Twenty neurotypical adults completed two identical sessions on the same day, separated by at least two hours, using a single-degree-of-freedom wrist robot. Outcomes were the kinematic detection threshold (degrees) for JDT and the mean absolute matching error (degrees) for J-to-J and J-to-V. Relative reliability was quantified with ICC (2,1) and 95% confidence intervals. Absolute reliability was quantified with the standard error of measurement (SEM) and the smallest detectable change at 95% confidence (SDC 95). Learning effects and differences across task levels were evaluated with paired t-tests or Wilcoxon signed-rank tests. Results. ICC (2,1) was 0.959 [95% CI: 0.900 to 0.980] for JDT, 0.837 [0.640 to 0.930] for J-to-J, and 0.769 [0.500 to 0.900] for J-to-V. The %SEM ranged from 11.9% (J-to-J) to 15.6% (J-to-V). SDC95 was 0.85, 1.71, and 3.54 degrees for JDT, J-to-J, and J-to-V, respectively. A small but significant practice effect was observed for JDT, but this was below the SDC95, and no learning effect was observed for J-to-J or J-to-V. We also observed that the absolute error increased monotonically across task levels, with all pairwise comparisons (JDT < J-to-J < J-to-V; all p < 0.01). Conclusions. All three tasks demonstrated good-to-excellent within-day relative reliability. Error scaled with the computational demand of each task, with the largest errors observed for the cross-frame task, which required a transformation between the visual and joint reference frames. The reported SDC95 values provide task-specific thresholds for distinguishing measurement noise from true change in future intervention studies. Inter-day reliability and validation in clinical populations are the next steps.

Physiological mirror activity (pMA) is the increase in involuntary muscle activity observed on the contralateral side during unilateral voluntary movement in neurologically healthy participants. This cross-sectional study aimed to explore the relationship between pMA and corticomuscular coherence (CMC) during finger dexterity tasks in young and older adults. Thirty-one right-handed young adults and 24 older adults performed a left-hand finger dexterity task. Electroencephalogram (EEG) signals were recorded from C3 and C4, and electromyogram (EMG) signals were collected from bilateral finger flexors and extensors. pMA was quantified as the change in right-hand EMG from rest to task. Gamma-band CMC was calculated from task-related EEG-EMG pairs, and its association with pMA was analyzed. In young adults, greater pMA was associated with lower CMC (C3- and C4-right flexors), whereas in older adults, greater pMA was associated with higher CMC (C3-left flexor). Young adults may suppress pMA emergence by appropriately monitoring and inhibiting activity, in the hand not performing the task. Conversely, in older adults, the mobilization of the ipsilateral motor cortex may have contributed to pMA emergence. This study suggests that the neuromuscular mechanisms involved in pMA during finger dexterity tasks differ between young and older adults.

Background and purpose: Patellofemoral pain syndrome (PFPS) is a multifaceted condition where proximal, local, and distal factors may contribute to symptoms and limitations. How these factors collectively contribute to PFPS remains poorly understood. Therefore, this study compared proximal, local, and distal mechanical characteristics between individuals with and without PFPS and investigated their association with pain intensity and functional disability. Methods: Eighty participants were included: 40 individuals with unilateral or bilateral PFPS, 40 healthy controls. Isometric muscle strength of hip, trunk, and ankle was assessed using a handheld dynamometer. Joint alignment (Q-angle, rearfoot angle, pelvic tilt) and muscle flexibility (iliotibial band, hamstrings, quadriceps, gastrocnemius, and soleus) were measured using standard clinical techniques. Pain severity was assessed using a visual analog scale (VAS), and functional disability was evaluated using the Kujala score. Results: Individuals with PFPS showed reduced iliotibial band flexibility, decreased hamstring and soleus length, lower hip abductor strength, and greater anterior and lateral pelvic tilt (all p < 0.02). Multivariate analysis identified reduced iliotibial band flexibility (OR = 7.48) and greater anterior pelvic tilt (OR = 11.75) as independent associates of PFPS. Anterior pelvic tilt predicted pain severity, while anterior trunk muscle strength and Q-angle predicted disability. Discussion: Reduced iliotibial band flexibility and increased anterior pelvic tilt were independently associated with PFPS, while anterior pelvic tilt predicted pain severity and anterior trunk muscle strength and Q-angle predicted functional disability. Clinical assessment and rehabilitation of PFPS should therefore extend beyond the knee to include iliotibial band flexibility, pelvic alignment, and trunk muscle strength.

While movement variability is a natural element of human expression, in sign languages it may affect mutual understanding, learning, and potential overuse injury. Sign language variability is not well-understood in part because quantitative analytical methods are yet to be clearly defined. Hence the aim of this study was to assess intra-subject reliability across repeated sessions for three signers, to identify features sensitive to experience-related differences in motor control consistency, and to establish movement consistency metrics for treating sign language kinematic differences as linguistically meaningful. Three signers were assigned to three different proficiency levels of sign language: Deaf (D), proficient (P), and student (S). Sign production variables were evaluated using intraclass correlation coefficients (ICCs) and coefficients of variation(CVs).Most kinematic features showed good to excellent ICCs such as duration, path length, signing space volume, and average and peak velocity. Some EMG features such as mean forearm amplitudes and co-contraction also showed good to excellent ICCs. These data can be used to improve the scientific investigation of sign languages, improve educational resources, and establish baseline thresholds to inform ergonomic or scheduling guidelines for interpreters.

Long-latency stretch reflex and corticospinal excitability in the tibialis anterior muscle (TA) are facilitated when balance is threatened, even without background TA activity, suggesting supraspinal modulation as preparatory tuning for ankle stabilization. However, it remains unclear whether such tuning is evident at the spinal level and specific to the TA among lower-limb muscles. We therefore examined the effects of height-induced postural threat on multi-segmental monosynaptic spinal reflexes (MMR) in lower-limb muscles during quiet standing. Seventeen healthy young males performed 90-s standing tasks under three postural threat conditions, created by combining real and virtual reality (VR) heights: (1) Low-threat (real ground & VR ground), (2) Medium-threat (real table & VR ground), and (3) High-threat (real table & VR bridge). During each condition, transcutaneous spinal cord stimulation (tSCS) was applied to the lumbar spine to elicit MMR in lower-limb muscles. Electromyograms (EMG) were recorded from six muscles of the right leg: vastus medialis (VM), biceps femoris (BF), TA, soleus (SOL), medial (MG), and lateral gastrocnemius (LG). MMR excitability was quantified as peak-to-peak EMG amplitude. Fear ratings and electrodermal activity were higher in High-threat than Low-threat (all p < 0.05), confirming successful threat induction. Peak-to-peak EMG amplitude in the TA was significantly higher in High-threat than Low-threat (17.1% increase, p = 0.0393), whereas background TA activity remained absent across conditions. These results indicate that TA has unique function to facilitate spinal excitability as a preparatory tuning for ankle stabilization. Key pointsO_LIPrevious studies have shown the supraspinal facilitation of the tibialis anterior muscle without background muscle activation as a preparatory tuning for ankle stabilization. C_LIO_LITo test the hypothesis that such tuning is also evident at the spinal level and specific to the tibialis anterior muscle, this study examined whether height-induced postural threat modulates multi-segmental monosynaptic reflex excitability in lower-limb muscles using transcutaneous spinal cord stimulation. C_LIO_LIElectrodermal activity and fear ratings increased under height-induced postural threat, confirming the successful induction of postural threat. C_LIO_LIUnder height-induced postural threat, the multi-segmental monosynaptic reflex was selectively facilitated in the tibialis anterior muscle, while its background activity remained absent. C_LIO_LIOur findings demonstrate selective facilitation of spinal excitability in the tibialis anterior muscle, which may serve as preparatory tuning for ankle stabilization under threat to balance. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/742625v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@ca21f3org.highwire.dtl.DTLVardef@7b1679org.highwire.dtl.DTLVardef@1007191org.highwire.dtl.DTLVardef@1ff88a_HPS_FORMAT_FIGEXP M_FIG C_FIG Abstract figure legendWhen balance is threatened, corticospinal excitability and long-latency stretch reflex in the tibialis anterior muscle (TA) are facilitated even in the absence of background TA activity, suggesting supraspinal preparatory tuning for ankle stabilization. This study tested the hypothesis that such facilitation is also expressed at the spinal level and is specific to the TA. Participants completed 90-s quiet standing trials under three different height-induced postural threat conditions. During each trial, transcutaneous spinal cord stimulation was delivered over the lumbar spine to elicit multi-segmental monosynaptic reflexes (MMR) in multiple lower-limb muscles. High-threat condition increased fear ratings and electrodermal activity, indicating successful threat induction. Moreover, MMR excitability was selectively increased in the TA under High-threat condition despite the absence of background TA activity. These findings suggest that spinal facilitation is selectively expressed in the TA and may reflect preparatory tuning for ankle stabilization under threat to balance.

ObjectiveDescribe and compare the biomechanical severity of head acceleration events (HAEs) associated with diagnosed concussion in elite mens and womens rugby league using instrumented mouthguards (iMGs) and evaluate the diagnostic accuracy and screening performance of severity metrics within the current Head Injury Assessment (HIA) process. MethodsA prospective cohort of 398 men and 252 women from Super League teams wore iMGs across 515 matches. Following a matching and data quality screening procedure, 123 HIAs (106 men, 17 women) were matched to HAEs, 52 of which were diagnosed concussions (44 men, 8 women). High-magnitude asymptomatic control HAEs (22,676 men, 3,200 women) were sampled proportionally to the number of HIAs. A range of biomechanical severity metrics were calculated for HAEs. Statistical comparisons between outcomes were made. Receiver operating characteristic (ROC) analysis evaluated diagnostic accuracy (ability to predict diagnosed concussions within the HIA). Precision-recall analysis evaluated screening performance (ability to discriminate observable concussion signs from asymptomatic events). ResultsDiagnosed concussions had greater severity than asymptomatic HAEs across all metrics in both sexes. For diagnostic accuracy, area under the ROC curve ranged from 0.61 to 0.72 in men and 0.53 to 0.86 in women. For screening performance, optimal thresholds in several metrics provided theoretical improvements to precision over current thresholds used in rugby, but recall remained <0.20. ConclusionThese findings support integrating iMG-derived severity metrics into a multimodal, clinician-led HIA pathway as objective adjuncts for diagnosis and screening, while reinforcing that they cannot replace clinical judgement or other assessment modalities. What is already known on this topicInstrumented mouthguards are increasingly used in rugby to quantify head acceleration events and trigger Head Injury Assessment (HIA) alerts, but current screening thresholds based on simple peak kinematics have low sensitivity for identifying HAEs linked with visible concussion signs, and very few iMG-measured concussions, particularly in women, have been reported in current research. What this study addsThis study provides the largest dataset of iMG-measured concussions in any sport, shows that concussive HAEs are more severe than asymptomatic events across multiple biomechanical metrics in both sexes, and identifies several severity metrics with diagnostic accuracy comparable to existing HIA sub-tests and modest theoretical improvements over current screening thresholds. How this study might affect research, practice or policyThese findings support incorporating iMG-derived severity metrics as objective adjuncts within clinician-led HIA pathways, highlight the need for sex-inclusive iMG datasets and multimodal concussion identification, and may inform future refinement of iMG screening thresholds in elite rugby and other contact sports.

Background Clinical assessments of Amyotrophic Lateral Sclerosis (ALS) are typically collected infrequently in clinic visits and may not fully capture domain-specific functional decline in daily life. Digital Health Technologies (DHTs) can support remote monitoring, but passive free-living measures often require prolonged wear time and may be influenced by non-motor factors. This study evaluated whether short, standardized, at-home lower limb exercises recorded with ankle-worn accelerometers provide objective and interpretable measures of lower limb disease progression in ALS. Methods We analyzed data from 349 participants with ALS enrolled in the decentralized ALS Research Collaborative Study. Participants completed repeated self-entry ALS Functional Rating Scale-Revised (ALSFRS-RSE) assessments and wore bilateral ankle accelerometers during monitoring periods between September 2014 and January 2023. During each period, participants performed brief seated knee flexion-extension exercises at home. A previously developed signal processing pipeline was used to derive four exercise metrics: count, duration, intensity, and similarity. We examined baseline correlations with ALSFRS-RSE total and subdomain scores, longitudinal change using linear mixed-effects models, associations with gross motor item scores, differences by anatomical site of disease onset, and comparisons with free-living gait metrics. Results At baseline, exercise-derived metrics, particularly intensity and similarity, showed the strongest associations with the gross motor subdomain. Longitudinally, duration increased while intensity and similarity decreased, consistent with progressive slowing, reduced movement vigor, and reduced movement consistency (all p < 0.001); count did not change significantly. Worsening responses to gross motor items related to turning in bed, walking, and stair climbing were consistently associated with fewer, slower, less vigorous, and less consistent lower limb repetitions. Baseline intensity and similarity were lower in participants with lower limb disease onset on the corresponding side. Exercise-derived intensity showed model fit comparable to the strongest free-living gait metrics, while requiring substantially less observation time. Conclusions Short at-home lower limb exercises recorded using ankle-worn accelerometers provide scalable, objective, and interpretable measures of amyotrophic lateral sclerosis-related functional decline. Movement quality metrics, particularly intensity and similarity, may complement passive free-living monitoring and support remote digital clinical outcome assessment in ALS research. Trial registration NCT06885918.

Objective and scalable approaches for detecting subtle motor impairment in isolated REM sleep behavior disorder (iRBD), a prodromal stage of Parkinson's disease, remain limited. We investigated whether markerless motion capture from single RGB-camera videos can identify gait abnormalities in people living with iRBD and provide interpretable digital biomarkers. We retrospectively analyzed 93 standardized walking videos from three clinical sites. Human pose estimation extracted 12 body markers and 14 kinematic time series. Thirty-five machine learning approaches classified healthy controls (HC) and people with iRBD. The Movement Disorder Society Unified Parkinson's Disease Rating Scale Part 3 (MDS-UPDRS III) served as the clinical baseline. The best-performing model (tsfresh+XGBoost) achieved an AUROC of 0.739, significantly outperforming the MDS-UPDRS III sum score when trained on data from all three sites. Harmonized multi-site training improved performance. SHAP identified hip-related temporal features as key contributors, which differed between groups and showed stronger associations with regional dopaminergic deficits than clinical scores. Single-camera gait analysis may provide scalable digital biomarkers for low-cost screening and monitoring of prodromal PD.

BackgroundFreezing of gait (FOG) in Parkinsons disease is associated with abnormal beta activity in the subthalamic nucleus (STN), but the temporal structure of burst dynamics remains poorly understood. ObjectivesTo determine whether temporal features of STN beta bursts distinguish pre-freeze from stable gait and predict freezing onset. MethodsSTN recordings during gait from four individuals were analyzed. Temporal features of burst timing, including entropy and variability, were computed across behavioral states. Predictive performance was assessed using leave-one-patient-out classifiers. ResultsEntropy of inter-burst intervals was reduced prior to freezing (p < 0.01), with strong predictive performance (AUC = 0.825; threshold AUC = 0.858). During freezing, variability measures decreased and temporal structure increased, while entropy did not differ from pre-freeze. Phase-amplitude coupling showed frequency-specific but heterogeneous effects across comparisons. ConclusionsReduced temporal variability of STN beta burst timing precedes and predicts freezing, suggesting a transition to constrained neural dynamics.

Prosthesis non-use and abandonment remain common among people with lower-limb amputation, yet current outcome measures capture only limited aspects of how prostheses are used in everyday life. Clinical assessments are typically conducted in controlled settings and rely on self-report or aggregate activity counts, which do not adequately represent functional performance, physiological effort, or lived experience during real-world prosthesis use. Wearable and ambient sensing offer a means of addressing this gap, but existing approaches tend to measure single dimensions in isolation and are rarely validated against laboratory reference standards before free-living deployment. This protocol describes an integrated multimodal framework for assessing real-world lower-limb prosthesis use across three complementary domains: classification of activities of daily living, estimation of energy expenditure, and assessment of emotional state. Approximately 40 adults with unilateral transfemoral or transtibial amputation complete a two-phase protocol. In the laboratory phase, wearable inertial, physiological, and ambient sensing are validated against established reference standards, including video annotation and indirect calorimetry. In the free-living phase, validated models are applied during a single seven-day home monitoring period, unifying all three domains within one deployment. A defined data harmonisation and quality-control procedure aligns heterogeneous sensor streams and preserves traceability between laboratory calibration and free-living measurement, enabling reproducible interpretation of functional behaviour, metabolic cost, and momentary emotional experience in relation to established clinical outcome domains. By integrating multimodal sensing at the level of study design rather than post-hoc analysis, the framework provides a validated, reproducible methodology for characterising prosthesis use beyond the capacity of conventional instruments, offering a transferable approach for real-world monitoring in rehabilitation research