Search Results (139)

Objective: To evaluate the feasibility of adding antigravity treadmill training (ATT) or harness-based body-weight-supported treadmill training (BWSTT) to standard inpatient rehabilitation after primary hip or knee arthroplasty and to explore preliminary effects on osteoarthritis-related outcomes, balance, and psychological status. Methods: In this single-center, assessor-blinded pilot randomized trial, 60 adults within 3 months after primary hip or knee arthroplasty for osteoarthritis were allocated 1:1:1 to ATT, BWSTT, or standard inpatient rehabilitation over 6 weeks. Feasibility outcomes included recruitment, retention, and adherence. ATT and BWSTT additionally included unloading-based treadmill gait training using lower-body positive pressure or a harness system. Exploratory clinical outcomes included WOMAC total and subscale scores, analyzed using baseline-adjusted ANCOVA estimated marginal means. Secondary exploratory outcomes were BBS, FES-I, PHQ-9, and PSS-10. Results: Post-intervention data were available for 47 participants, with differential attrition across groups. Exploratory ANCOVA suggested between-group differences for WOMAC total (p = 0.004) and WOMAC function (p < 0.001). Compared with standard rehabilitation, ATT showed lower adjusted WOMAC total and function scores (both p < 0.01). ATT versus BWSTT contrasts for WOMAC total and function were statistically significant in the primary exploratory model but attenuated after hypertension adjustment. Exploratory signals were also observed for BBS and FES-I, although FES-I was less robust in sensitivity analysis. No clear between-group differences were observed for WOMAC pain, stiffness, PHQ-9, or PSS-10. No formal multiplicity adjustment was applied across exploratory endpoints. Conclusions: In this single-center pilot randomized trial, ATT suggested preliminary function- and balance-related signals that require confirmation in adequately powered multicenter trials. Full article

Stress shielding (SS) after cementless total hip arthroplasty arises from the stiffness mismatch between conventional Ti-6Al-4V femoral stems (110 GPa) and cortical bone (10–30 GPa). The β-type Ti-33.6Nb-4Sn (TNS) alloy femoral stem addresses this limitation through a continuous Young’s modulus gradient (~70 GPa proximally to ~40 GPa distally) achieved by localized heat treatment of a single homogeneous alloy. This review synthesizes a translational research program encompassing material characterization, finite element modeling (FEM), preclinical animal studies, and prospective clinical follow-up of up to seven years. FEM demonstrated favorable proximal micromotion well below the osseointegration threshold, with physiological proximal stress concentration concordant with clinical outcomes. At seven years, SS grade distribution was significantly lower in the TNS group than in Ti-6Al-4V controls, with SS frequency reduced in Gruen Zones 2, 3, and 6, and no stem-related failures; however, third-degree SS was still observed in 11 of 34 evaluable cases (32%), indicating that modulus-gradient optimization alone is insufficient to fully prevent SS. TNS alloy is currently the only β-type titanium alloy clinically applied in joint prostheses. Remaining challenges include stem geometry optimization, additive manufacturing-based porous structures, and dual-energy X-ray absorptiometry-based bone density quantification. Future directions encompass long-term follow-up, cyclic fatigue FEM simulations, and expansion to fracture fixation devices and dental implants. Full article

Background/Objectives: Post-stroke gait impairment is highly heterogeneous, which limits the effectiveness of standardized exoskeleton control strategies. Deep reinforcement learning offers a route to adaptive assistance, but its use in stroke rehabilitation is constrained by limited pathological gait data and the lack of interpretable transfer frameworks. We developed a data-efficient, pathology-informed reinforcement learning framework for personalized exoskeleton assistance under limited clinical gait data. Methods: The framework combines neuromuscular-inspired parametric augmentation (NIPA) with parameter-efficient transfer learning. NIPA synthesizes pathological gait trajectories by modeling weakness, stiffness or contracture, and abnormal synergies. A policy is first pretrained in simulation and then adapted to clinical gait data by freezing a shared feature extractor and fine-tuning the output heads. The framework was evaluated on a public clinical gait dataset of 50 stroke survivors using tracking error, reward, smoothness, generalization, and data efficiency as main outcomes. Results: The proposed method outperformed zero assistance, rule-based control, and reinforcement learning from scratch on the test set. Compared with scratch, it reduced total MSE from 14.8681 to 11.9369 ($p=5.96\times {10}^{-8}$) and improved reward from −21.2264 to −18.4798 ($p=3.76\times {10}^{-4}$). Hip MSE decreased from 5.9544 to 4.0143 ($p=7.51\times {10}^{-8}$) and knee MSE decreased from 6.5507 to 5.4507 ($p=1.51\times {10}^{-5}$), with significant improvements in repeated experiments. Conclusions: The proposed framework reduces reliance on large pathological training datasets and improves offline trajectory-level personalization under limited clinical data. It also provides an interpretable basis for quantitative characterization of post-stroke gait heterogeneity and may support individualized rehabilitation assessment and assistance planning. Full article

Bone resorption secondary to stress shielding is a leading cause of hip implant failure, primarily due to the stiffness mismatch between the femur and the prosthesis. Although anatomical stem designs generally provide improved load transfer, Dorr type C femurs often require straight stems to ensure adequate primary stability. This work presents a systematic approach to designing a straight, additively manufactured porous titanium hip stem aimed at minimizing stress shielding. The lattice architecture is customized to replicate the mechanical properties of bone based on patient-specific femoral CT scans. The performance of the resulting porous implant is numerically assessed under simplified physiological gait loading conditions. The implant behavior is evaluated through a homogenization strategy to model the lattice structure, significantly reducing the computational effort and making the methodology easily replicable. Compared to its full counterpart, the porous design achieves a significant reduction in predicted bone loss, suggesting that the proposed framework is a promising proof of concept for patient-specific implants. While further experimental validation and larger cohort studies are required, these findings highlight the potential of mechanically tunable porous structures to mitigate the stress shielding phenomenon in anatomical conditions such as Dorr type C femurs, which require straight stems. Full article

Conventional gel electrodes are the gold standard for surface electromyography (sEMG), yet their bulkiness, stiffness, and limited gel lifetime prevents seamless day-long integration with wearable robots. We integrated ultrathin skin-conformal temporary tattoo electrodes with a powered unilateral hip exoskeleton and compared signal quality during treadmill walking against gel. In this pilot study, five healthy participants completed three consecutive walking blocks at fixed speed: (1) using gel electrodes; (2) using tattoo electrodes to compare signal quality; and (3) using the same tattoo electrodes (not repositioned) after eight hours of wear to simulate a full day of typical device use and to evaluate potential degradation in signal quality over time. Electrodes were positioned on muscles not covered by the exoskeleton interface (tibialis anterior and gastrocnemius medialis), as well as on muscles located beneath the exoskeleton cuff, which were potentially subject to motion artifacts due to the application of external forces by the exoskeleton (rectus femoris and biceps femoris, BF). Across all muscles, for both gel and tattoo electrodes, the root mean square error (RMSE) between normalized sEMG envelopes and biological activation profile was 0.069 ± 0.048, and Pearson’s correlation coefficient (ρ) was 0.844 ± 0.091. Re-testing the same tattoo electrode pair after eight hours confirmed day-long stability without the need for recalibration. Statistical analysis revealed no significant differences in signal quality, also when applying assistive forces, between the two electrode types and across all muscles (RMSE, all p ≥ 0.3125; ρ, all p ≥ 0.1250), as well as no degradation after eight hours (RMSE and ρ: all p ≥ 0.0626, uncorrected). Finally, in a proof-of-concept session, BF activity measured with tattoo electrodes was found reliable to drive hip-extension assistance in real time. Collectively, these results show that tattoo electrodes deliver signal quality comparable to gel electrodes while offering a low-profile skin-conformal interface and day-long usability, making them a promising option for enhancing EMG-based control in wearable robots. Full article

Anterior cruciate ligament (ACL) injury risk is elevated in female youth football, yet knee joint loading has mainly been studied under controlled laboratory conditions. This limits understanding of how injury risk emerges during realistic match situations. This study provided a field-based kinetic characterization of football-specific movements by estimating knee abduction moments (KAMs) using wearable sensors and machine learning. Fifty-two highly talented female youth players performed agility tasks during training, including structured exercises (F-EX) and game-based play (F-GAME). Full-body kinematics were collected with inertial measurement units, and a validated support vector machine model, trained on synchronized motion capture and force plate data, classified trials as high or low KAM. Across 662 change-in-direction trials, 9–12% were classified as high KAM in both conditions, indicating that potentially high-risk loading regularly occurs during routine actions. High KAM trials showed reduced knee and pelvis flexion, increased hip flexion, and greater pelvis rotation toward the cutting direction, reflecting upright, stiff movement strategies. Performance analyses revealed smaller cut angles in exercises and greater approach acceleration in game play, without differences in peak velocity. These findings demonstrate the feasibility of field-based kinetic screening and support a complex-systems perspective on ACL injury risk. Full article

Traditional ready-to-wear garments can mostly not conform to different body shapes because of the adoption of the generic sizing system, which leads to the local strain of concentration and morphological misfit. Auxetic structures, which have a negative Poisson’s ratio, permit enhanced redistribution of stress and geometry and allow deformation. Two auxetic knitted structures were developed by using 100% polyester and 100% nylon yarns with a fabric density of 41 Wales and 40 courses per inch. Characterization of the initial fabrics involved checking the behavior of negative Poisson’s ratio (NPR) where the polyester line (P1) structure shows the highest auxeticity, with a NPR of approximately −0.4 and peak strain reductions of 80–90%, as well as air permeability, moisture management, bend test, compression, roughness, friction properties and stiffness tests to check the mechanical and comfort-related performances. The standardized tunic garment was modeled in CLO 3D on three female body shapes—hourglass, pear and rectangle—with a constant size of 34. The fit map showed a strain of 91.49% in auxetic and 509.75% in single-jersey fabric at the hip area of the pear body shape when measuring fabric and body interaction. The findings indicate lower peak strain levels, which ascertain that increased adaptability is possible and support its use in the development of adaptive ready-to-wear garments. Full article

Background/Objectives: Osgood–Schlatter disease (OSD) is a common overuse condition in adolescents characterized by increased stiffness of the rectus femoris muscle, which contributes to pain and functional limitations around the knee. We investigated whether repeating 10 min passive joint movements of the hip and knee produces additional immediate reductions in elevated rectus femoris (RF) stiffness in adolescents with OSD. Methods: Fifteen patients (10–14 years of age) diagnosed with bilateral OSD were included. The legs of the participants were randomly assigned to either the intervention or the non-intervention side (control). The intervention side received two sets of 10 min of passive joint movement to the hip and knee, while the control side rested. RF stiffness was measured before the intervention and immediately after one and two sets of passive joint movements. Results: On the intervention side, RF stiffness decreased significantly from pre to post-1 and from pre to post-2; however, RF stiffness did not differ significantly between post-1 and post-2. None of the parameters changed significantly on the control side (rest condition). Conclusions: Passive joint exercise beyond one repetition (one set for 10 min) did not result in a further decrease in RF stiffness and is likely unnecessary for RF muscle stiffness due to OSD. Full article

Tibial torsion significantly influences knee biomechanics, yet its interaction with ACL reconstruction history in elite alpine skiers remains under-investigated. In this cross-sectional observational study, we analyzed 20 elite alpine skiers (7 ACL-reconstructed, 13 non-injured) using a markerless motion capture system during dynamic tasks (Squat, Single-Leg Squat, Lunge). Static tibial torsion was assessed via the Transmalleolar Axis and Thigh–Foot Angle. The results revealed a critical divergence in biomechanical strategies based on tibial alignment (p < 0.05). Skiers with rotational deformity adopted a pattern we describe as a “Stiffness Strategy”, characterized by suppressed knee valgus and hip rotation, but relied on excessive ankle dorsiflexion (39.5°)—a compensatory mechanism that may become limited when constrained by rigid ski boots. In contrast, ACL-reconstructed skiers with normal alignment exhibited what we term an “Instability Strategy”, showing dynamic valgus collapse and persistent asymmetry. These findings suggest that “one-size-fits-all” rehabilitation may be insufficient. We propose that injury prevention protocols may benefit from incorporating anatomical screening, focusing on decoupling mobility for skiers with tibial torsion and enhancing dynamic stability for those with normal alignment. Full article

Background: The viscoelastic properties of muscle tissue are important factors affecting muscle performance; they play a significant role in maintaining spinal stability, as well as muscle contraction and function. Changes in these properties can result in pain, restricted movement, or poor posture. However, there is limited information in the literature regarding the viscoelastic properties of the paraspinal muscles, such as tone and stiffness, in individuals with chronic low back pain, which is one of the most common musculoskeletal disorders. The main aim of our study was to investigate the effects of reformer Pilates exercises on muscle viscoelastic properties in individuals with chronic low back pain for 4 weeks. In addition, our secondary aim was to examine the effects of Pilates-based exercises on body anthropometric values, pain intensity, functionality and kinesiophobia levels, sleep, and quality of life in individuals with chronic low back pain and to compare these parameters with a healthy group without low back pain. Methods: The study was carried out in a private clinic center and involved a total of 52 participants: 24 healthy subjects (control group) and 28 subjects with chronic low back pain (CLBP group). Pilates-based exercises were applied 2 days a week for 8 sessions for a total of 4 weeks. Muscle viscoelastic properties, body anthropometric values, pain intensity, functional status, kinesiophobia, sleep quality, and quality of life of all cases were evaluated. Muscle viscoelastic values were measured with a portable myotonometer, MyotonPro. Results: After 4 weeks of Pilates-based training, no significant improvements were observed in the parameters of muscle tone and stiffness in both groups (p > 0.05). It was found that pain intensity (p = 0.001), sleep quality (p = 0.004), quality of life (p = 0.019), and disability level (p = 0.003) improved after 4 weeks of Pilates-based training in subjects with chronic low back pain. In addition, there were significant differences in the parameters of the chest, waist, hip, and thigh circumferences after 4 weeks of Pilates-based training, except for the abdomen, in both groups (p < 0.05). Conclusions: A period of four weeks of Pilates exercises did not lead to significant changes in the muscle viscoelastic properties of the lumbar and abdominal muscles, although performing these exercises did result in regional thinning. The efficacy of Pilates exercises in reducing pain, disability, and kinesiophobia and in improving sleep and quality of life has been demonstrated in individuals suffering from chronic low back pain. Full article

Background/Objectives: Exercise-induced fatigue is a fundamental component of running performance and training, yet it is also implicated in altered movement mechanics and increased injury risk. While numerous studies have examined fatigue-related biomechanical changes during running, findings remain fragmented across biomechanical domains and fatigue modalities. The purpose of this systematic review was to synthesize contemporary evidence on the effects of fatigue on lower-limb biomechanics during running and to interpret the potential injury relevance of these adaptations. Methods: A systematic literature search was conducted in PubMed, Scopus, and Web of Science for original empirical studies published between January 2010 and December 2025. Eligible studies involved human participants performing running or running-related tasks, applied an explicit fatigue protocol, and reported quantitative lower-limb biomechanical outcomes. Study selection followed PRISMA 2020 guidelines. Data extraction included participant characteristics, fatigue protocols, biomechanical measures, instrumentation, and key findings. Methodological quality was assessed using the Cochrane Risk of Bias 2 (RoB-2) tool. Due to substantial methodological heterogeneity, findings were synthesized narratively. Results: Twenty-four studies met the inclusion criteria. Across studies, fatigue consistently altered spatiotemporal parameters, joint kinematic and kinetic variables, spring-mass behavior, impact loading, coordination variability, neuromuscular output, and inter-limb symmetry. Common adaptations included increased ground contact time, reduced ankle joint power and stiffness, increased joint range of motion, elevated impact loading, and greater movement variability. These changes reflected reduced mechanical efficiency and a redistribution of mechanical load from distal to proximal joints, particularly toward the knee and hip. Similar fatigue-related biomechanical patterns were observed in both laboratory-based and real-world endurance running conditions. Conclusions: Exercise-induced fatigue produces systematic and injury-relevant alterations in lower-limb biomechanics during running. These adaptations may preserve short-term performance but create mechanical conditions associated with increased susceptibility to overuse and non-contact injuries. Integrating fatigue-aware biomechanical assessment, neuromuscular conditioning, and individualized load management strategies may help mitigate adverse fatigue-related adaptations. Full article

Background/Objectives: Blood Flow Restriction training has been suggested as a method to enhance strength and neuromuscular adaptations at low exercise intensities. Early reports indicate potential effects on pain perception, myofascial stiffness, and flexibility; however, the evidence remains inconsistent. Method: Twenty-two healthy adults participated in a randomized, within-participant, contralateral-controlled design, performing 5 min of treadmill walking (4–5 km/h) with and without blood flow restriction at 70% arterial occlusion pressure. Pressure pain threshold, hip range of motion, and hamstring stiffness were measured before and after the intervention. Adverse effects were recorded. Results: Changes in pain threshold, range of motion, and myofascial stiffness were similar between conditions. The pressure pain threshold decreased slightly in both conditions, regardless of BFR, while range of motion and stiffness remained unchanged. Mild, short-lasting sensations (cuff pressure, erythema, tingling) were reported, with no adverse events. Conclusions: A single short session of low-intensity BFR walking did not change pain sensitivity, flexibility, or myofascial stiffness in healthy adults. The protocol was well tolerated. Repeated or longer interventions may be needed to see measurable effects. Full article

This study systematically investigated the influence of approach kinematics on the subsequent kinetics and power production strategies during the approach to running jumps with a single leg (ARJSL). Twenty-five physically active male university students performed ARJSL trials under two prescribed approach speeds (fast and slow) and three approach distances (3, 6, and 9 m) in a 2 × 3 within-subjects design. Three-dimensional motion capture synchronized with force platform data was used to quantify jump height (JH), vertical touchdown velocity (TDv), reactive strength index (RSI), peak joint power (hip, knee, and ankle), and joint stiffness. Significant approach speed × distance interactions were observed for JH (p = 0.006), TDv (p < 0.001), RSI (p = 0.014), ankle stiffness (p = 0.006), and peak power generation at all lower-limb joints (all p < 0.034). The results demonstrate that changes in approach strategy systematically alter the distribution of mechanical power among the hip, knee, and ankle joints, thereby influencing the effectiveness of horizontal-to-vertical momentum conversion during take-off. Notably, RSI and ankle stiffness were particularly sensitive to combined manipulations of speed and distance, highlighting their value as neuromechanical indicators of stretch–shortening cycle intensity and joint loading demands. In conclusion, ARJSL performance depends on finely tuned, speed- and distance-specific biomechanical adaptations within the lower extremity. These findings provide a constrained, joint-level mechanical characterization of how approach speed and distance interact to influence power redistribution and stiffness behavior during ARJSL, without implying optimal or performance-maximizing strategies. Full article

Purpose: This study investigated how variations in approach speed and distance influence lower-limb muscle activation, joint co-contraction ratios (CCRs), and mechanical joint stiffness during single-leg approach run jump landings (ARJSL), to clarify adaptive neuromuscular strategies for joint stiffness regulation. Methods: Twenty-five physically active male university students performed ARJSLs under six randomized conditions combining two approach speeds (fast > 4.0 m/s; slow < 4.0 m/s) and three approach distances (3, 6, and 9 m). Surface electromyography (sEMG) from five dominant-limb muscles—rectus femoris, biceps femoris, tibialis anterior, gastrocnemius, and soleus—was analyzed across three movement phases: pre-activation, downward (braking), and push-off. Knee and ankle CCRs were computed, while kinematic and kinetic data were used to calculate mechanical joint stiffness via inverse dynamics. A two-way repeated-measures ANOVA evaluated the main and interaction effects of approach speed and distance. Results: Significant speed × distance interactions were observed for tibialis anterior activation, several CCRs, and eccentric ankle stiffness (p < 0.05). Pre-activation knee CCR increased with longer, faster approaches, indicating anticipatory joint pre-stiffening. During braking, greater ankle co-contraction under fast–9 m conditions coincided with reduced mechanical ankle stiffness, suggesting a compensatory yielding strategy under high kinetic loads. In the push-off phase, faster approaches elicited higher concentric stiffness at the hip and ankle, supporting efficient energy transfer. Rectus femoris and gastrocnemius activation scaled with both approach speed and distance. Conclusions: Athletes adapt neuromuscular co-contraction and mechanical stiffness in a coordinated, phase-dependent manner to balance protection and performance. These insights may inform targeted training strategies for enhancing jump efficiency and mitigating ACL injury risk. Full article

This paper presents a lower-limb hip exoskeleton system integrated with an adjustable-stiffness flexible energy-storage module for three-dimensional gait correction. This system features a modular flexible mechanical design and a stiffness-gain scheduled PID control strategy for dynamic, personalized assistance. Based on biomechanical analysis of the hip joint, a 3D gait correction model was constructed targeting impairments in flexion, abduction, and adduction. The control strategy adjusts system stiffness in real-time according to gait phase and user-specific parameters. Experimental results demonstrated that the exoskeleton effectively reduced joint trajectory variability (22% decrease in standard deviation of hip flexion angle) and improved muscle activation patterns (21.4% increase in rectus femoris activity), thereby enhancing gait symmetry and stability. This study offers a feasible mechatronic solution for pathological gait correction with promising clinical applicability. Full article