Search Results (107)

Preclinical testing is essential for evaluating new implant designs and materials for total knee replacement (TKR). Standardized wear tests, such as ISO 14243, are widely accepted but only partially represent physiological kinematics and kinetics, as they do not account for all six degrees of freedom of the knee joint. More advanced setups, including robotic systems and joint simulators, enable complex load cases; however, the influence of lubrication conditions and testing speeds remains insufficiently standardized. This study investigated the kinematic and kinetic effects of different lubrication conditions (dry, synthetic synovial fluid, silicone oil) and speeds (static, 10%, 50%, 100% of normal gait) in a joint simulator setup using a posterior cruciate ligament-retaining TKR during level walking. Complementary pin-on-disk measurements revealed significant dependencies on both lubrication and speed. During joint simulator tests, omitting lubrication resulted in more than double the maximum flexion–extension moment, while the range of anterior–posterior femoral translation increased by approximately 73%. At 50% and 100% speed, silicone lubrication yielded results comparable to static tests, in contrast to the dry and synthetic synovial fluid conditions. These findings demonstrate that physiologically relevant lubrication and appropriate test speeds are essential for obtaining reliable results in experimental studies of TKR dynamics. Full article

Background/Objectives: Serum albumin has antioxidant, anti-inflammatory, and antithrombotic properties and reflects nutritional status. Hypoalbuminemia is linked to cognitive decline and frailty. However, the relationship between serum albumin levels and brain structural changes in older adults remains unclear. We aimed to examine the associations between serum albumin levels and total brain, hippocampal, and white matter lesion volumes in cognitively normal, community-dwelling older Japanese adults, accounting for frailty status. Methods: In this cross-sectional study, 7266 participants aged ≥65 years without cognitive decline were included. Serum albumin levels, maximum handgrip strength, and usual gait speed were measured in all participants. Brain magnetic resonance imaging scans were used to evaluate total brain, hippocampal, and white matter lesion volumes. Results: Lower serum albumin levels were significantly associated with smaller total brain and hippocampal volumes after multivariable adjustment (both p for trend < 0.001; partial η² = 0.005), but not with white matter lesion volumes (p for trend = 0.24; partial η² = 0.001). In subgroup analyses stratified by frailty status, no significant heterogeneity in the associations between serum albumin levels and each brain volume was observed between groups defined by maximum handgrip strength or usual gait speed. Conclusions: Lower serum albumin levels are associated with smaller total brain and hippocampal volumes in cognitively normal, community-dwelling older Japanese adults, irrespective of frailty status. Serum albumin may serve as a clinically accessible marker of nutritional conditions in relation to these brain structures in older adults. Full article

Mongolian horses are an indigenous Chinese breed known for their endurance capacity, yet quantitative descriptions of their gait-related kinematic characteristics remain limited. This pilot exploratory study aimed to describe the kinematics of Mongolian horses during walk, slow trot, and fast trot, and to examine whether selected variables differed between race-result groups in a 12 km endurance race. Forty-six horses were classified into an excellent group and an ordinary group based on the result of a single race. Kinematic data were collected using optical motion capture and three-dimensional skeletal modelling. Separate gait-specific linear mixed-effects models were fitted, with horse identity as a random effect and group and speed as fixed effects. The results showed gait-dependent between-group differences. During walk, the excellent group had significantly greater range of motion of the tarsal, hip, and elbow joints, as well as a greater maximum forelimb retraction angle (all p < 0.001). During slow trot, the excellent group showed significantly greater stride length (p = 0.009), elbow joint range of motion (p < 0.001), minimum hindlimb forward extension angle (p = 0.033), and minimum forelimb forward extension angle (p = 0.004). During fast trot, the between-group differences were most pronounced, with significantly greater stride length (p < 0.001) and range of motion of the tarsal joint (p < 0.001), hip joint (p = 0.015), and elbow joint (p = 0.014), together with greater maximum hindlimb retraction angle (p = 0.001) and minimum forelimb forward extension angle (p = 0.026). Overall, these findings provide preliminary evidence that gait-related kinematic differences may exist between race-result groups in Mongolian horses. However, because this was an exploratory study based on a single race, the findings should be interpreted cautiously and require validation in larger and more diverse cohorts. Full article

Cognitive impairment is a prevalent non-motor manifestation of Parkinson’s disease (PD), yet early detection remains limited by the sensitivity of conventional cognitive assessments. Emerging evidence suggests that motor dysfunction, particularly gait and balance abnormalities, reflects underlying cognitive vulnerability. This study examined motor–cognitive associations and evaluated whether motor-derived features can be used to classify low-MoCA status in PD without direct cognitive testing. Data from 102 individuals with PD were analyzed, incorporating clinical assessments, physical function measures, lifestyle factors, and gait-derived biomarkers. Multiple regression identified Unified Parkinson’s Disease Rating Scale Part III, stride length of the more affected side during 360° turning at preferred speed, and maximum ankle jerk on the less affected side during forward walking as independent predictors of Montreal Cognitive Assessment scores, collectively explaining 34.7% of the variance. Network analysis revealed integrative relationships among global motor severity, gait smoothness, and cognitive performance. Using a compact motor-based feature set, logistic regression achieved a mean accuracy of 65.8% and an AUC of 0.737 in classifying low-MoCA status under cross-validation. These findings demonstrate that motor-derived digital biomarkers capture clinically meaningful information about cognitive status in PD and may serve as adjunctive tools for identifying cognitive vulnerability in clinical settings. Full article

In this paper, an improved state-space method (SSM) is proposed for gait feature extraction. By introducing zero-phase component analysis Whitening (ZCA Whitening) and an algorithm to search estimated echo as the preprocessing method, pedestrian echoes are divided into three groups according to the frequency probability density: torso, feet, and other segments. Two channels of echoes are selected as inputs to the SSM, which is employed to identify the corresponding micro-Doppler trajectory. On this basis, five gait features of torso amplitude, stride length, walking cycle, torso maximum speed, and feet maximum speed are extracted. Simulation based on the Boulic model, compared with the traditional SSM, demonstrated that there is no need to estimate the model order and that a more accurate torso micro-Doppler trajectory and effective micro-motion features of the feet can be obtained by the proposed method. Finally, 77 GHz FMCW radar was used to collect the echoes of four pedestrians. The classifier was designed based on a support vector machine (SVM), and the classification experiment verified the effectiveness of the extracted gait features. Full article

Lower-limb rehabilitation exoskeletons must balance biomechanical compatibility, structural safety, and low mass to enable practical, repeatable gait assistance. This paper proposes a planar pantograph-derived exoskeleton leg driven by a Chebyshev Lambda linkage and develops an integrated workflow from mechanism synthesis to manufacturable optimization and experimental verification. A mannequin-coupled multibody model was built in MSC ADAMS to evaluate joint kinematics, end-point (foot) trajectories, and joint reaction forces under multiple scenarios (fixed-frame, ramp, stair ascent, and inclined-plane walking). The extracted joint loads were transferred to a parametric finite element model in ANSYS Workbench 2019, where response surface surrogates and a multi-objective genetic algorithm (MOGA) were used to minimize mass under stiffness and strength constraints. For the optimized load-bearing link, the selected minimum-mass design reached a component mass of 0.542 kg while respecting the imposed structural limits, i.e., a maximum total deformation below 0.2 mm and a maximum equivalent (von Mises) stress below 50 MPa (e.g., ~0.188 mm deformation and ~39 MPa stress in the optimal candidate). A rapid prototype was manufactured by 3D printing and experimentally evaluated using CONTEMPLAS high-speed video tracking, providing measured X_M(t) and Y_M(t) trajectories and joint-angle histories for quantitative comparison with simulations via RMSE metrics. Full article

Background/Objectives: Foot impairments are common in older adults, but the independent associations of specific foot indices with locomotive syndrome (LS) severity remain unclear. We examined hallux valgus angle (HV), navicular height (NH), and passive ankle dorsiflexion (ADF). Methods: This cross-sectional study included 119 community-dwelling older adults classified into LS stages 0–3. Bilateral measures were summarized as maximum HV and minimum NH/ADF, reflecting the worst-affected side. Proportional-odds ordinal logistic regression modeled LS stage (0–3) with foot indices and covariates (age, sex, body mass index [BMI]). Extended models additionally adjusted for Timed Up and Go (TUG), gait speed, or single-leg stance (SLS). Sensitivity analysis used binary logistic regression (LS ≥ 2 vs. <2). Results: Greater ADF was independently associated with lower LS severity (OR per 1°, 0.91; 95% CI, 0.85–0.98; p < 0.01), whereas higher BMI was associated with greater LS severity (OR per 1 kg/m², 1.15; 95% CI, 1.01–1.30; p < 0.05). HV and NH were not significant. After adjustment for TUG, gait speed, or SLS, ADF remained inversely associated with LS severity (ORs, 0.92–0.93; p < 0.05), while the BMI association was attenuated. In binary logistic regression, greater ADF was associated with lower odds of LS ≥ 2 (OR per 1°, 0.85; 95% CI, 0.76–0.94; p < 0.005). Conclusions: Reduced passive ankle dorsiflexion is independently associated with greater LS severity, robust after accounting for key mobility and balance measures. Interventions targeting ankle mobility may represent a potentially modifiable factor and warrants confirmation in longitudinal and interventional studies. Full article

Walking on compliant terrain presents a substantial challenge for individuals with lower-limb amputation, further elevating their already high risk of falling. While powered ankle–foot prostheses have demonstrated adaptability across speeds and rigid terrains, control strategies optimized for soft or compliant surfaces remain underexplored. This work experimentally validates an admittance-based control strategy that dynamically adjusts the quasi-stiffness of powered prostheses to enhance gait stability on compliant ground. Human subject experiments were conducted with three healthy individuals walking on two bilaterally compliant surfaces with ground stiffness values of 63 and $25{\displaystyle \frac{\mathrm{kN}}{\mathrm{m}}}$, representative of real-world soft environments. Controller performance was quantified using phase portraits and two walking stability metrics, offering a direct assessment of fall risk. Compared to a standard phase-variable controller developed for rigid terrain, the proposed admittance controller reduced short-term maximum Lyapunov exponents by an average of 7%, indicating improved local dynamic stability. These results support the potential of adaptive prostheses control to enhance gait stability on compliant surfaces, contributing to the development of more robust human–prosthesis interaction. Full article

To enhance the flexibility and adaptability of underwater robots in complex environments, this paper designs an octopus-inspired soft underwater robot capable of both bipedal walking and multi-arm swimming. The robot features a rigid–flexible coupling structure consisting of a head module and eight rope-driven soft tentacles and integrates buoyancy adjustment and center-of-gravity balancing systems to achieve stable posture control in both motion modes. Based on the octopus’s bipedal walking and multi-arm swimming mechanisms, this study formulates gait generation strategies for each mode. In walking mode, the robot achieves underwater linear movement, turning, and in-place rotation through coordinated tentacle actuation; in swimming mode, flexible three-dimensional propulsion is realized via synchronous undulatory gaits. Experimental results demonstrate the robot’s peak thrust of 14.1 N, average swimming speed of 8.6 cm/s, and maximum speed of 15.1 cm/s, validating the effectiveness of the proposed structure and motion control strategies. This research platform offers a promising solution for adaptive movement and exploration in unstructured underwater environments. Full article

Background: Juvenile Idiopathic Arthritis (JIA) is a chronic inflammatory condition that can disrupt joint function and biomechanics, often leading to altered gait patterns. When coexisting with secondary scoliosis—a common musculoskeletal complication in children with JIA—postural and movement impairments may be further exacerbated. However, limited research has investigated the combined impact of JIA and secondary scoliosis on gait characteristics. This study aimed to evaluate gait parameters in children diagnosed with JIA and secondary scoliosis and to compare them with age-matched healthy peers. Methods: A total of 50 children (25 with JIA and secondary scoliosis, 25 healthy controls) were included. Demographic data, plantar pressure distribution, temporal gait parameters, and center of mass (CoM) displacement were assessed using computerized gait analysis. Group comparisons were performed using appropriate statistical methods. Results: Children with JIA and secondary scoliosis exhibited significantly lower forefoot loading on both dominant and non-dominant sides compared to controls (p < 0.05). Maximum loading values were also reduced bilaterally in the JIA group (p < 0.001). The dominant side single-limb support duration was significantly shorter (p = 0.027), and CoM displacement was greater (p = 0.044) in the JIA group. No differences were observed in rearfoot loading or walking speed. Conclusions: Children with coexisting JIA and secondary scoliosis demonstrate altered gait mechanics, likely reflecting compensatory adaptations due to joint inflammation and postural asymmetries. Gait analysis may offer valuable insights for tailoring rehabilitation strategies in this patient population. Full article

Background: Clinical assessment of gait typically consists of patients walking a few trials at various speeds while the clinician assesses performance. Unfortunately, there is no clear guidance on how gait changes across trials, leaving clinicians uncertain about the optimal number of trials needed to observe consistent (non-variable) performance. To address this issue, we examined gait performance from a large dataset of older adults who participated in a community-based comprehensive fall risk assessment. Methods: Community-dwelling, older adults (n = 340; 70.8 ± 7.4 years; 120 men, 220 women) performed gait trials under two conditions: preferred and maximum walking speed. Individuals were encouraged to complete five trials for both conditions. Consistency between gait trials within each condition was calculated using intraclass correlation (ICC) and standard error of measurement (SEM) analysis. Results: Our data showed the middle three trials had the most consistency compared to the average of 2–5 trials. Conclusions: When performing a clinical gait analysis, the first trial should be used to acclimate the participant to the protocol and not used for analysis. Data should be recorded from the next three trials, which is when gait appears to stabilize. Data from a fifth trial differs from the second trial, potentially indicating fatigue and/or motivation changes, so it is recommended that the gait analysis conclude after the fourth trial. Full article

Background: Motor adaptation is a process where movements need to be modified in response to changes in the task, environment, or organism itself. Even a very short-term process of adaptation to different movement execution conditions leads to improvements in task performance. There is no information in the literature on whether such a gain would be present in older adults with different fear of falling levels (FoF). Methods: Thirty older adults with various FoF underwent short-term adaptive gait training on a treadmill. Participants’ spatiotemporal and foot loading characteristics were assessed directly before and after stimulation in two walking conditions: with preferred speed, and in challenging conditions (maximum speed). Results: Correlation analysis revealed moderate-to-strong associations with fear (0.66–0.74) in a majority of spatiotemporal parameters, as well as in rear and forefoot loading (0.48–0.82). In more challenging conditions, observed associations were more pronounced; however, comparative analysis revealed that the correlation was significantly stronger only in stride length (p = 0.03), walking speed (p = 0.03), forefoot (p = 0.01), and rearfoot loading (p = 0.02). There was a marginal effect of adaptive training during walking with preferred speed, but in demanding conditions, results showed significant improvements in each fear level group. Conclusions: The correlation between fear and plantar loading during walking in older adults implies a more cautious foot roll-over pattern with increasing FoF. Results also suggest that the relationship between fear and detrimental gait changes scales to some extent with motor task difficulty. The data suggest preserved but possibly attenuated gait adaptability in highly fearful older adults. Full article

Colombian Paso horses (CPs) excel in gait competitions due to their endurance, speed, and precision, which demand a high level of cardiorespiratory fitness. However, their training regimes often lack scientific support, and few studies have linked physiological parameters to optimal training zones. This study aimed to estimate the aerobic lactate threshold (LTaer) using mathematical methods and to correlate it with heart rate (HR) zones and blood lactate. Eighteen CPs were evaluated and classified into trained (GT) and untrained (GD) groups. All animals underwent a field-based incremental exercise test (IET) with continuous HR monitoring and serial blood sampling for lactate, creatinine, BUN, AST, and CK analysis. LTaer was estimated using three methods: visual inspection, and fixed thresholds at 2 mmol/L (ZL2), and 4 mmol/L (ZL4). HR zones corresponding to each threshold were then calculated based on a maximum estimated HR of 220 bpm. The visual method placed LTaer in zone 2 for both groups. ZL2 located the threshold in zone 2 for GT and in zone 3 for GD, whereas ZL4 placed the threshold in zone 4 for both groups. Although no intergroup differences in lactate or HR were observed, intragroup differences emerged above 75% of HRmax, indicating exponential lactate accumulation. Biochemical parameters revealed significant pre- to post-exercise changes, but no differences between groups, suggesting a standardized workload. This is the first study to propose field-based prediction of LTaer in CPs using HR derived from wearable technologies, based on blood lactate and a standardized exercise test’s results. Correlating HR zones with lactate thresholds facilitates workload analysis in the field. Future studies should investigate the maximal lactate steady state (MLSS) in this breed. Full article

Background and Objectives: Type 2 diabetes mellitus (T2DM) is a major public health issue worldwide that leads to reductions in skeletal muscle mass and lower-limb function, thereby increasing the risk of locomotive syndrome (LS), a mobility-limiting condition. This study investigated the effects of a 5-month, lower limb-focused, low-intensity resistance exercise program using slow movements (slow exercise) on LS in patients with T2DM. Materials and Methods: Nineteen patients with T2DM (69.3 ± 7.3 years, 10 men and 9 women) performed slow exercises three times per week for 5 months. The program consisted of bodyweight and machine-based exercises with a load of 30–50% one-repetition maximum using slow concentric–isometric–eccentric phases. Assessments included HbA1c, LS stage distribution (non-LS, LS-1, LS-2, LS-3), LS risk tests (two-step, stand-up, and GLFS-25), five-time sit-to-stand test, four-meter gait speed, and skeletal muscle mass index (SMI) and phase angle (PhA) by bioelectrical impedance analysis. Statistical comparisons were performed using repeated one-way ANOVA with Tukey’s post hoc test and Cochran’s Q test. Results: HbA1c decreased from 7.5 ± 0.7% to 7.2 ± 0.8% (p < 0.05). LS stage distribution improved significantly (stage 3: 4 to 0; non-LS: 1 to 5; each p < 0.05). The two-step test and GLFS-25 improved (1.17 ± 0.15 to 1.27 ± 0.17; 14.6 ± 13.1 to 7.6 ± 6.3; each p < 0.05). Five-time sit-to-stand time improved from 9.28 ± 2.53 s to 7.73 ± 1.54 s, and four-meter gait speed improved from 3.58 ± 0.95 s to 3.07 ± 0.55 s (each p < 0.05). SMI and PhA increased (6.82 ± 1.00 to 6.95 ± 0.92 kg/m²; 4.35 ± 0.67 to 4.56 ± 0.78 degrees; each p < 0.05). Conclusions: A 5-month slow exercise program significantly improved LS severity, muscle quantity and quality, and lower-limb function in patients with T2DM. Slow exercise may be a safe and effective intervention to improve mobility and maintain independence in this population. Full article

Diabetes mellitus often leads to peripheral neuropathy that compromises protective sensation in the feet and raises ulcer risk through mechanical overload. While prior research has introduced cellular-metamaterial-based shoe midsoles for dynamic plantar pressure redistribution, this study advances the field by delivering a complete, application-oriented workflow for physical prototyping and mechanical validation of such structures. Our pipeline integrates analytical synthesis of curved-beam unit cells, process calibration, and fabrication via thermoplastic polyurethane (TPU) fused-filament fabrication, producing customized, test-ready lattices suitable for future gait-simulation studies and in vivo assessment. Printed TPU tests showed a Young’s modulus of 44.5 MPa, ultimate tensile strength of 4.9 MPa, and strain at break ≈ 20% (Shore 84.5 A/37.2 D). The cellular unit’s compressive response was quantified by theoretical force-threshold estimates and controlled compression tests, enabling data-driven selection of unit cell geometry and arrangement for effective offloading. The response is rate-dependent: higher loading speed increases peak force and hysteresis, indicating that loading rate should be treated as a design parameter to tune dynamic behavior for the target application. Although the analytical model overestimates forces by roughly 50% on average relative to experiments, it accurately captures the influence of key geometric parameters on peak force. Accordingly, experimental data can identify cell strategic geometric parameters (i.e., Q), while the achievable maximum force can be predicted from the model by applying an appropriate correction factor. By connecting modeling, calibration, and experimental validation in one coherent path, the proposed workflow enables manufacturable lattices with controllable activation thresholds for plantar pressure redistribution and provides a practical bridge from concept to application. Full article