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14 pages, 4207 KB

Open AccessArticle

Machine Learning Identifies Distinct Biomechanical Gait Phenotypes in Pediatric and Adolescent Ataxia: Establishing a Clinical Decision Model

by Weerasak Tapanya and Noppharath Sangkarit

Biomechanics 2026, 6(2), 44; https://doi.org/10.3390/biomechanics6020044 - 7 May 2026

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Abstract

Background: Standard clinical scales for pediatric and adolescent ataxia lack biomechanical granularity, limiting precision rehabilitation. This study aimed to identify compensatory gait phenotypes using unsupervised machine learning and establish a robust, highly accessible clinical decision model. Methods: Spatiotemporal gait data from [...] Read more.

Background: Standard clinical scales for pediatric and adolescent ataxia lack biomechanical granularity, limiting precision rehabilitation. This study aimed to identify compensatory gait phenotypes using unsupervised machine learning and establish a robust, highly accessible clinical decision model. Methods: Spatiotemporal gait data from 51 youths (31 ataxia and 20 healthy controls) were analyzed. To ensure pathological specificity, Principal Component Analysis (PCA) and hierarchical clustering were applied exclusively to 13 biomechanical variables from the ataxia cohort (n = 31) to extract underlying domains and identify patient subgroups. Healthy controls were subsequently used as a normative reference. A Classification and Regression Tree (CRT) algorithm was developed for clinical translation. Results: Two distinct phenotypes reflecting the evolution of compensatory strategies were identified: a “Rapid Rhythm” strategy (n = 24) and a severe “Prolonged Stance” strategy (n = 7). Unlike previous assumptions, the phenotypes strongly correlated with clinical severity (Scale for the Assessment and Rating of Ataxia (SARA) scores: 9.79 vs. 16.78, p = 0.012) and exhibited significantly different gait speeds (p < 0.001). The CRT model identified the stance phase duration as the primary discriminator. A recalibrated critical cut-off of >69.68% effectively classified the severe Prolonged Stance phenotype. This threshold sits distinctly above the healthy pediatric norm, achieving an overall cross-validated accuracy of 96.8%, with 100% specificity. Conclusions: Gait phenotypes in pediatric and adolescent ataxia represent progressive stages of neuromechanical compensation driven by disease severity. The established 69.68% stance-phase threshold provides clinicians with a powerful, single-variable biomechanical red flag to identify severe pathological gait and guide phase-specific precision rehabilitation. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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13 pages, 1504 KB

Open AccessArticle

Comparison of Quantitative Evaluation Methods for Pathological Gait Abnormalities in Stroke Survivors

by Kento Sabashi and Ryo Ueno

Biomechanics 2026, 6(2), 39; https://doi.org/10.3390/biomechanics6020039 - 15 Apr 2026

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Abstract

Background/Objectives: The Gait Variable Score (GVS) and Gait Abnormality Score (GAS) have been proposed as methods for quantitatively evaluating deviations from normal gait patterns. This study aimed to investigate whether the GVS or GAS is more useful for evaluating gait in stroke [...] Read more.

Background/Objectives: The Gait Variable Score (GVS) and Gait Abnormality Score (GAS) have been proposed as methods for quantitatively evaluating deviations from normal gait patterns. This study aimed to investigate whether the GVS or GAS is more useful for evaluating gait in stroke survivors. Methods: We used open-access motion capture datasets from 43 stroke survivors and 82 healthy individuals. Nine kinematics and seven muscle activities were extracted. The GVS was calculated as the root mean square difference between the pathological and healthy gait patterns. The modified GAS (mGAS) newly defined in this study was calculated as the mean value of the absolute differences between the pathological and healthy gait patterns divided by the standard deviation of healthy gait patterns. The amplitudes of kinematics and muscle activities were calculated. Results: Both the GVS and mGAS were significantly higher in stroke survivors than in healthy individuals. A significant strong correlation for 16 variables (nine kinematics and seven muscle activities) was observed between the GVS and amplitude (r = 0.921), but no significant correlation was found between the mGAS and amplitude (r = 0.167). Conclusions: As the mGAS is not affected by the amplitude of kinematics and muscle activities, it allows for a comprehensive comparison of abnormalities in both kinematics and muscle activities. The mGAS may be more useful than the GVS for evaluating gait abnormalities in stroke survivors. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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12 pages, 971 KB

Open AccessCommunication

by Rute Vieira e Magalhães Rodrigues, Beatriz Regina Legutke, Gabriel Antonio Gazziero Moraca, Thiago Martins Sirico, Murilo Lorencetti Torres, Diego Orcioli-Silva and Victor Spiandor Beretta

Biomechanics 2026, 6(1), 17; https://doi.org/10.3390/biomechanics6010017 - 3 Feb 2026

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Abstract

Background/Objectives: People with Parkinson’s disease (PwPD) exhibit impairments in postural responses to perturbations, increasing their risk of falls. While transcranial direct current stimulation (tDCS) has been shown to enhance postural responses in PwPD, its effects considering history of falls remain unclear. Thus, we [...] Read more.

Background/Objectives: People with Parkinson’s disease (PwPD) exhibit impairments in postural responses to perturbations, increasing their risk of falls. While transcranial direct current stimulation (tDCS) has been shown to enhance postural responses in PwPD, its effects considering history of falls remain unclear. Thus, we aimed to analyse the effect of tDCS on postural responses after external perturbation in PwPD with and without a history of falls. Methods: Twenty-two PwPD were distributed into two groups—faller (n = 12) and non-faller (n = 10)—based on their history of falls over the 12 months preceding the experiment. A 20 min anodal tDCS was applied to the primary motor cortex (M1) under two conditions (2 mA and sham), performed on two different visits (at least 2 weeks apart) with a randomised order. Seven trials with temporally unpredictable external perturbation (i.e., backward translation of the support base) were performed after tDCS. Electromyographic (i.e., medial gastrocnemius (MG) onset latency, magnitude of muscle activation of MG and tibialis anterior (TA), and MG/TA coactivation index) and centre of pressure (CoP) parameters (i.e., range of CoP, peak of CoP velocity, and recovery time) were analysed to assess postural response. A two-way ANOVA (Group × Stimulation Condition) was performed. Results: Both groups had shorter recovery time (determined by CoP) and MG onset latency in the active vs. sham condition. Conclusions: The results of our pilot study suggest that a single 20 min tDCS session (2 mA) applied over M1 enhances postural responses similarly in PwPD with and without a history of falls in the past year. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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13 pages, 2403 KB

Open AccessArticle

Local Dynamic Stability During the 1-Minute Sit-to-Stand Test: Directional Differences and Associations with Body Composition in Healthy Adult Women

by Arunee Promsri, Punnakan Pitiwattanakulchai, Siwaporn Saodan and Salinrat Thiwan

Biomechanics 2026, 6(1), 14; https://doi.org/10.3390/biomechanics6010014 - 2 Feb 2026

Cited by 1 | Viewed by 663

Abstract

Background: The 1 min sit-to-stand test (1-MSTST) is a widely used functional assessment involving repetitive sit-to-stand transitions. This study examined local dynamic stability during the 1-MSTST across three acceleration directions, compared young and middle-aged women, and explored associations between body composition and stability. [...] Read more.

Background: The 1 min sit-to-stand test (1-MSTST) is a widely used functional assessment involving repetitive sit-to-stand transitions. This study examined local dynamic stability during the 1-MSTST across three acceleration directions, compared young and middle-aged women, and explored associations between body composition and stability. Methods: Twenty-four young adult women (24.1 ± 5.2 years) and twenty-four middle-aged women (51.4 ± 5.9 years) performed the 1-MSTST. Trunk accelerations were recorded using a tri-axial accelerometer at L5. Local dynamic stability was quantified using the largest Lyapunov exponent (LyE), and movement magnitude using root mean square (RMS). Directional, group, and correlational analyses were performed with correction for multiple testing. Results: Significant directional differences were observed for both LyE and RMS, with all pairwise contrasts between mediolateral (ML), anteroposterior (AP), and vertical (VT) directions remaining significant after correction (p < 0.001). Apparent age effects in LyE were no longer significant after adjusting for cadence, BMI, and multiple testing, indicating no robust age-related difference in local dynamic stability. Body fat percentage showed moderate positive correlations with LyE in the VT (p = 0.003) and AP (p = 0.003) directions. Muscle mass percentage showed a moderate positive correlation with VT LyE (p = 0.002) and moderate negative correlations with ML (p = 0.002) and AP LyE (p = 0.002). Conclusions: Stability during the 1-MSTST differs by direction, with the greatest variability in the mediolateral axis. No independent age effect was found. Higher body fat relates to poorer stability, while greater muscle mass supports better movement control. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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14 pages, 951 KB

Open AccessArticle

Does Speed-Normalized Double-Support Reflect Gait Stability in Parkinson’s Disease? A Model-Based Analysis

by Noppharath Sangkarit and Weerasak Tapanya

Biomechanics 2025, 5(4), 102; https://doi.org/10.3390/biomechanics5040102 - 4 Dec 2025

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Abstract

Background: Double-support percentage (DS%) is often interpreted as a proxy for dynamic gait stability, yet its biomechanical meaning is confounded by its strong inverse coupling with walking speed. This distinction is critical in Parkinson’s disease (PD), where bradykinetic gait inherently prolongs DS%. To [...] Read more.

Background: Double-support percentage (DS%) is often interpreted as a proxy for dynamic gait stability, yet its biomechanical meaning is confounded by its strong inverse coupling with walking speed. This distinction is critical in Parkinson’s disease (PD), where bradykinetic gait inherently prolongs DS%. To isolate speed-independent stability demands, we introduced a model-based Stability Reserve Index (SRI), representing the deviation between predicted and observed double support after normalizing for velocity and anthropometrics. Methods: Using an open-access dataset of 63 individuals with PD (ON medication; Hoehn & Yahr 1–3) and 63 matched controls, step-based DS% was modeled using ANCOVA, incorporating centered walking speed, group, their interaction, and covariates. Predicted DS% at the sample’s grand mean speed was subtracted from observed DS% to derive the SRI, indexing whether double support exceeded expectations for a given biomechanical operating point. Results: PD participants walked slower than controls (p < 0.001), but once velocity was accounted for, DS% no longer differed between groups (p = 0.795–0.880), and the DS%–speed coupling remained intact (interaction p = 0.387). Speed-normalized predicted DS% (p = 0.159) and the SRI (p = 0.989) were likewise similar across groups. Within PD, SRI did not correspond to UPDRS-III or Hoehn & Yahr stage (ρ = 0.129–0.223, p > 0.05). Conclusions: These findings indicate that double-support behavior in mild-to-moderate PD is largely velocity-driven rather than reflecting altered dynamic stabilization strategies. While conceptually grounded in stability reserve theory, the SRI showed limited discriminatory value under ON-medication walking, suggesting that more sensitive multidimensional metrics—integrating CoM dynamics, variability, and step-to-step control—may be required to capture early instability in PD. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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20 pages, 7649 KB

Open AccessArticle

The Mechanistic Causes of Increased Walking Speed After a Strength Training Program in Stroke Patients: A Musculoskeletal Modeling Approach

by Georgios Giarmatzis, Nikolaos Aggelousis, Erasmia Giannakou, Ioanna Karagiannakidou, Evangelia Makri, Anna Tsiakiri, Foteini Christidi, Paraskevi Malliou and Konstantinos Vadikolias

Biomechanics 2025, 5(4), 97; https://doi.org/10.3390/biomechanics5040097 - 1 Dec 2025

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Abstract

Background/Objectives: While strength training interventions improve walking performance in stroke survivors, the underlying neuromuscular mechanisms remain poorly understood. This study investigated muscle-level adaptations following a 12-week moderate-to-high-intensity strength training program in ten chronic stroke survivors using comprehensive musculoskeletal modeling analysis. Methods: Three-dimensional gait [...] Read more.

Background/Objectives: While strength training interventions improve walking performance in stroke survivors, the underlying neuromuscular mechanisms remain poorly understood. This study investigated muscle-level adaptations following a 12-week moderate-to-high-intensity strength training program in ten chronic stroke survivors using comprehensive musculoskeletal modeling analysis. Methods: Three-dimensional gait analysis was performed pre- and post-intervention, with subject-specific OpenSim models estimating individual muscle forces, powers, and work capacities throughout stance phase. Results: Non-paretic hip flexor negative work capacity increased significantly (0.033 to 0.042 J/kg, p = 0.033, Cohen’s d = 0.47), driven by enhanced rectus femoris power absorption during late stance that mechanistically facilitated trunk acceleration through leg deceleration. Knee extensor force generation showed increasing trends during loading response in both limbs. During push-off, ankle plantar flexor force generation showed trends toward bilateral improvements, primarily through paretic soleus and gastrocnemius contributions, though power output remained unchanged, indicating persistent velocity-dependent muscular deficits. Conclusions: Improved gait performance in both limbs demonstrates that strength training produces functionally beneficial bilateral muscle-level reorganization. The absence of a control group limits causal inference, though the observed biomechanical adaptations align with functional improvements, supporting the integration of strength training into comprehensive stroke rehabilitation protocols targeting locomotor recovery. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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8 pages, 675 KB

Open AccessArticle

Impact of Walking Path Length on Gait Parameters During the 2-Minute Walk Test in Healthy Young Adults

by Cecilia Lo Zoppo, Valeria Belluscio and Giuseppe Vannozzi

Biomechanics 2025, 5(4), 82; https://doi.org/10.3390/biomechanics5040082 - 10 Oct 2025

Cited by 2 | Viewed by 1719

Abstract

Background/Objectives: The 2-minute walk test (2MWT) is a time-based gait assessment commonly employed for populations with limited walking ability for greater tolerability compared to the longer 6-minute test. The recommended distance to perform the tests is a 30 m straight path, a space [...] Read more.

Background/Objectives: The 2-minute walk test (2MWT) is a time-based gait assessment commonly employed for populations with limited walking ability for greater tolerability compared to the longer 6-minute test. The recommended distance to perform the tests is a 30 m straight path, a space requirement that is not always available in non-laboratory contexts. Shorter paths are therefore often adopted, but associated changes in gait patterns are not clear. The aim of the study is therefore to investigate how different walking path lengths affect gait patterns during the 2MWT. Methods: Twenty healthy young adults performed three walking trials on a straight hallway of 5 m, 15 m, and 30 m lengths. Spatiotemporal gait parameters were measured using three inertial measurement units on both distal tibiae and at pelvis level. Results: The 5 m path showed the greatest deviations, specifically in walking distance, walking speed, stride duration, stance time, swing time, single support time, and cadence, if compared to longer distances (p < 0.05). The 15 m path showed differences only in walking distance and walking speed (p < 0.05), if compared to the 30 m path. Conclusions: Shorter path lengths, particularly the 5 m, significantly impact gait patterns and should be considered when interpreting 2MWT results in clinical settings. The 30 m path is recommended as the gold standard, with 15 m as a viable alternative for assessing temporal parameters. Nevertheless, the extent to which each feature would be over/underestimated when walking in limited spaces is also addressed. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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9 pages, 1024 KB

Open AccessBrief Report

Increased Hip-Flexion Gait as an Exercise Modality for the Reduction of Knee Joint Contact Forces: A Preliminary Investigation

by Tanner Thorsen and Nuno Oliveira

Biomechanics 2025, 5(3), 66; https://doi.org/10.3390/biomechanics5030066 - 2 Sep 2025

Cited by 2 | Viewed by 2029

Abstract

Background: Increased hip-flexion gait (HFgait) has been shown to promote increased aerobic demands by increasing peak swing-phase hip-flexion angles while walking at comfortable speeds. Biomechanically, HFgait produces a gait pattern similar to walking, while removing the flight phase from running and reducing [...] Read more.

Background: Increased hip-flexion gait (HFgait) has been shown to promote increased aerobic demands by increasing peak swing-phase hip-flexion angles while walking at comfortable speeds. Biomechanically, HFgait produces a gait pattern similar to walking, while removing the flight phase from running and reducing tibial accelerations. We sought to identify knee joint contact forces between HFgait and common exercise modalities, including running, walking, and cycling, across intensity levels. Methods: Ten healthy participants completed two bouts (low and high intensity) of four different exercises: treadmill running, walking, HFgait, and cycling. Tibiofemoral joint compressive force (TCF) was estimated using a static optimization-based approach. Results: Peak TCF was greater in running compared to HFgait, walking, and cycling; greater in HFgait compared to cycling; and greater in walking compared to cycling. The integral of TCF (iTCF) was greater in running compared to cycling, greater in HFgait compared to running, walking, and cycling, and greater in walking compared to running and cycling. Conclusions: HFgait produced lower knee joint loading than running, comparable joint loading to walking, and greater joint loading than cycling. Thus, HFgait may serve as an exercise modality for populations where joint loading is of particular concern, while achieving aerobic demands similar to running or increased functional demands compared to stationary cycling. Full article

(This article belongs to the Special Issue Gait and Balance Control in Typical and Special Individuals: Second Edition)

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