Search Results (577)

Recent reports have revealed that the number of lower limb amputees worldwide has increased as a result of war, accidents, and vascular diseases and that transfemoral amputation accounts for 39% of cases, highlighting the need to develop an improved functional prosthetic knee joint that improves the amputee’s ability to resume activities of daily living. To enable transfemoral prosthesis users to walk on level ground, accurate prediction of the intended knee joint angle is critical for transfemoral prosthesis control. Therefore, the purpose of this research was to develop a technique for estimating knee joint angle utilizing a long short-term memory (LSTM) network and kinematic data collected from inertial measurement units (IMUs). The proposed LSTM network was trained and tested to estimate the contralateral knee angle using data collected from twenty able-bodied subjects using a lab-developed sensory gadget, which included four IMUs. Accordingly, the present work represents a feasibility investigation conducted on able-bodied individuals rather than a clinical validation for amputee gait. This study contributes to the field of bionics by mimicking the natural biomechanical behavior of the human knee joint during gait cycle to improve the control of artificial prosthetic knees. The proposed LSTM model learns the contralateral knee’s motion patterns in able-bodied gait and demonstrates the potential for future application in prosthesis control, although direct generalization to amputee users is outside the scope of this preliminary study. The contralateral LSTM models exhibited a real-time RMSE range of 2.48–2.78° and a correlation coefficient range of 0.9937–0.9991. This study proves the effectiveness of LSTM networks in estimating contralateral knee joint angles and shows their real-time performance and robustness, supporting its feasibility while acknowledging that further testing with amputee participants is required. Full article

Background: Static coronal alignment is considered a key of lower limb biomechanics after total knee replacement (TKR); however, its relationship with dynamic foot loading patterns and gait characteristics remains unclear. The primary objective of this prospective study was to investigate whether there is a correlation between dynamic plantar pressures and spatiotemporal parameters of gait and the coronal alignment of the lower limb after unilateral TKR for primary knee osteoarthritis (KOA). Methods: Thirty-two consecutive patients scheduled for TKR were evaluated preoperatively and at six months postoperatively. Changes in plantar pressure distribution and spatiotemporal gait parameters were collected using a multiplatform plantar pressure analysis system (PPAS), while coronal alignment was assessed using the femorotibial angle (FTA). Relationships with preoperative, postoperative, and correction-related alignment measures were examined using non-parametric statistical methods. Results: Dynamic plantar pressures and spatiotemporal gait parameters were not found to be consistently associated with pre- or postoperative values of FTA, respectively. Furthermore, the degree of correction did not appear to influence baropodometric outcomes. Conclusions: Static coronal alignment, as defined by the FTA, was not found to be consistently associated with dynamic plantar pressure patterns or spatiotemporal gait parameters at six months following unilateral TKR in our study population. These findings highlight the potential limitations of using solely static radiographic markers to evaluate complex functional outcomes such as gait. Full article

Background: This study aimed to explore the effects of neuromuscular electrical stimulation (NMES) combined with water-based resistance training on muscle activation and coordination during freestyle kicking. Methods: Thirty National Level male freestyle swimmers were randomly assigned to an experimental group (NMES + water-based training) or a control group (water-based training only) for a 12-week intervention. The experimental group received NMES pretreatment before each session. Underwater surface electromyography (sEMG) synchronized with high-speed video was used to collect muscle activation data and corresponding kinematic information during the freestyle kick. The sEMG signals were then processed using time-domain analysis, including integrated electromyography (iEMG), which reflects the cumulative electrical activity of muscles, and root mean square amplitude (RMS), which indicates the intensity of muscle activation. Non-negative matrix factorization (NMF) was further applied to extract and characterize muscle synergy patterns. Results: The experimental group showed significantly higher iEMG and RMS values in key muscles during both kicking phases. Within the core propulsion synergy, muscle weighting of vastus medialis and biceps femoris increased significantly, while activation duration of the postural adjustment synergy was shortened. The number of synergies showed no significant difference. Conclusions: NMES combined with water-based resistance training enhances muscle activation and optimizes neuromuscular coordination strategies, offering a novel approach to improving sport-specific performance. 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

Background: Long-distance hiking usually requires carrying a backpack, adding external load to the lower limbs and modifying plantar loading patterns. Excessive loads may contribute to overuse injuries, but quantitative evidence to support current recommendations on backpack weight is still scarce. This study aimed to examine how different backpack loads influence plantar pressure in long-distance hikers. Methods: A cross-sectional observational study was conducted in adults who had walked at least 20 km during the previous 24 h. Sociodemographic and clinical variables were recorded, and barefoot plantar pressure was assessed using the Podoprint^® system under four conditions: without a backpack, with the habitual backpack, and with backpacks loaded to 10% and 20% of body weight. Static and dynamic plantar pressure parameters were analyzed using repeated-measures comparisons. Results: A progressive increase in plantar force was observed in both feet as backpack load increased. Compared with the unloaded condition, static forefoot pressure rose by 5.41% with a 10% load and by 8.73% with a 20% load (p = 0.005); rearfoot pressure increased by 5.01% and 10.17% (p = 0.015); and total foot pressure by 5.04% and 9.61% (p = 0.002). Loads above 10% of body weight significantly modified static plantar pressures and were associated with measurable changes during dynamic assessment. Conclusions: In long-distance hikers, carrying a backpack that exceeds approximately 10% of body weight leads to a clear, load-dependent increase in plantar pressure. These findings provide biomechanical support for recommendations that advise limiting backpack load to around 10% of body weight to reduce plantar stress during hiking. Full article

Analyzing the dynamics of muscle activation patterns and joint range of motion is essential to understanding human movement during complex tasks such as tooth brushing Activities of Daily Living (ADLs). In individuals with neuromotor impairments, accurate assessment of upper limb motor patterns plays a critical role in rehabilitation, supporting the identification of compensatory strategies and informing clinical interventions. This study presents the validation of a previously developed novel, low-cost, wearable, and portable multimodal prototype that integrates inertial measurement units (IMU) and surface electromyography (sEMG) sensors into a single device. The system enables bilateral monitoring of arm segment kinematics and muscle activation amplitudes from six major agonist muscles during ADLs. Eleven healthy participants performed a functional task, tooth brushing, while wearing the prototype. The recorded data were compared with two established gold-standard systems, Qualisys^® motion capture system and Biosignalsplux^®, for validation of kinematic and electrophysiological measurements, respectively. This study provides technical insights into the device’s architecture. The developed system demonstrates potential for clinical and research applications, particularly for monitoring upper limb function and evaluating rehabilitation outcomes in populations with neurological disorders. Full article

Background: The integration of markerless motion capture systems such as OpenCap with force platforms expands the possibilities of biomechanical analysis in low-cost environments; however, it requires robust temporal synchronization procedures in the absence of shared hardware triggers. Objective: To develop and validate an automatic synchronization algorithm based on heel kinematic events to align OpenCap data with force platform signals during lower-limb functional exercises. Methods: Thirty normal-weight adult women (18–45 years) were evaluated while performing between 11 and 14 functional tasks (60° and 90° squats, lunges, sliding variations, and step exercises), yielding 330 motion records. Kinematics were estimated using OpenCap (four iPhone 12 cameras at 60 Hz), and kinetics were recorded using BTS P6000 force platforms synchronized with an OptiTrack system (Gold Standard). The algorithm detected heel contact from the filtered vertical coordinate and aligned this event with the initial rise in vertical ground reaction force. Validation against the Gold Standard was performed in 20 squat repetitions (10 at 60° and 10 at 90°) using Pearson correlation, RMSE, and MAE of the time-normalized and amplitude-normalized (0–1) vertical ground reaction force (vGRF). Results: The algorithm successfully synchronized 92.5% of the 330 records; the remaining cases showed kinematic noise or additional steps that prevented robust event detection. During validation, correlations were r = 0.85 (60°) and r = 0.81 (90°), with Root Mean Square Error (RMSE) < 0.17 and Mean Absolute Error (MAE) < 0.14, values representing less than 0.1% of the peak force. Conclusions: The heel-contact-based algorithm allows accurate synchronization of OpenCap and force platform signals during lower-limb functional exercises, achieving performance comparable to hardware-synchronized systems. This approach facilitates the integration of markerless motion capture in clinical, sports, and occupational settings where advanced dynamic analysis is required with limited infrastructure. 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

(1) Background: Endovascular therapy is widely used for lower limb peripheral artery disease (PAD), yet device performance varies across vascular territories due to anatomical and biomechanical differences. This study evaluated territory- and lesion-specific outcomes following contemporary endovascular strategies in a real-world cohort. (2) Methods: This retrospective single-center study included consecutive patients undergoing endovascular revascularization of the iliac, superficial femoral (SFA), or popliteal arteries between 2010 and 2023. The primary endpoint was 12-month binary restenosis (≥50% diameter loss) assessed by duplex ultrasonography, CT angiography, or invasive angiography. Secondary outcomes included target lesion revascularization and procedural complications. Kaplan–Meier analysis was used to evaluate restenosis-free survival. Multivariable Cox models were constructed separately for each vascular territory, adjusting for relevant clinical and anatomical covariates. (3) Results: A total of 283 lesions were included (iliac n = 135; SFA n = 145; popliteal n = 102). At 12 months, restenosis rates differed substantially by treatment modality and arterial territory. In the iliac segment, covered stents demonstrated the lowest restenosis (12.8%), whereas in the SFA, interwoven nitinol stents yielded the most favorable profile (15.4%). In the popliteal artery, drug-coated balloons were associated with the lowest restenosis rate (16.7%). In multivariable analysis, covered stents (iliac), interwoven nitinol stents (SFA), and drug-coated balloons (popliteal) were independently associated with lower restenosis risk. Procedural success was high and complication rates were low. (4) Conclusions: Endovascular device performance is strongly influenced by arterial territory and lesion characteristics. Tailoring the treatment strategy to vessel biomechanics and lesion morphology may optimize mid-term patency in lower limb PAD. Larger prospective studies are warranted to validate these findings. Full article

Cycling-based rehabilitation is a non-invasive intervention for individuals with lower limb asymmetries. However, current cycling devices lack comprehensive biomechanical feedback and cannot assess asymmetry. Our lab has developed a novel cycle ergometer equipped with three-dimensional force pedals, a seat post and handlebar force sensors, which allow for a comprehensive analysis of asymmetry across a fatiguing task. This study assessed the reproducibility of the cycling kinetics and asymmetry index derived from this device during incremental and constant load cycling tasks to volitional failure. Eighteen participants completed incremental and constant-load tests, each across two identical sessions. Pedal forces and power were analyzed for each leg individually, and handlebar forces and seat post mediolateral sway were recorded during cycling. Normalized symmetry index (NSI), a metric quantifying the degree of asymmetry between limbs, was calculated for each variable. The reproducibility of the device was assessed using repeated measures analysis of variance and intraclass correlation coefficients (ICC). No significant session or interaction effects were found for pedal, handlebar, and seat post measures (all p > 0.05). Time effects were observed for pedal force and power in the incremental test (all p < 0.001). NSI values were reproducible with high ICC values (≥0.70) for force and power. The results suggest that this ergometer offers reproducible cycling kinetics and asymmetry measures across a fatiguing task. The findings support the application of this ergometer in research and rehabilitation settings. Full article

Scapholunate (SL) ligament injuries, if not properly treated, can compromise wrist biomechanics, leading to instability, scapholunate advanced collapse (SLAC) and progressive osteoarthritis. Depending on the severity of the injury, current repair techniques include either arthroscopic or open surgical approaches; however, the limited vascularization of the region often represents an obstacle to optimal ligament healing. This study aims to assess the feasibility of using a vascularized fascial flap based on the 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) for biological augmentation of the scapholunate ligament. Five previously injected cadaveric upper limbs were dissected and flap dimensions, including length, width, and pedicle length, were measured using a millimeter-calibrated ruler by two independent operators. All flaps provided sufficient coverage, and the vascular pedicle length allowed tension-free positioning without vascular kinking. These findings demonstrate that a 1,2 ICSRA-based fascial flap is anatomically feasible for scapholunate ligament augmentation. It should be noted that this is a purely cadaveric study, and the technique has not yet been tested in vivo. The results suggest potential surgical applications, providing a vascularized biological option that may enhance ligament healing in future clinical studies. Full article

Background: The subacromial space, measured as the acromiohumeral distance (AHD), is a key determinant of shoulder biomechanics and injury risk. Athletes performing repetitive upper-limb resistance training are particularly exposed to cumulative tendon stress. Musculoskeletal ultrasound (US) enables dynamic, cost-effective assessment, yet its role in strength athletes remains underexplored. The aim of this study was to determine whether young adults engaged in regular upper-limb weight training present a narrower acromiohumeral distance and a higher prevalence of ultrasound-detected tendon abnormalities compared with non-weight-training individuals. Methods: We conducted a post hoc subanalysis of a cross-sectional cohort of 66 young adults (18–45 years; mean 29.6 ± 9.0 years; 27 men/39 women) evaluated with standardized shoulder US. Participants were classified as weight-training (n = 15; 36.2 ± 5.7 years; 11 men/4 women) or non-weight-training (n = 51; 27.6 ± 8.8 years; 16 men/35 women). AHD was measured in millimeters, and abnormalities of the supraspinatus, subscapularis, long head of the biceps tendon (LHBT), and subacromial–subdeltoid bursa were recorded. Between-group comparisons used Welch’s t-test or χ²/Fisher’s exact test; effect sizes were expressed as Cohen’s d or odds ratios (OR). Multiple testing was corrected with the false discovery rate (FDR). Results: Weight-training participants exhibited a significantly smaller AHD (7.13 ± 0.54 vs. 7.49 ± 0.68 mm; t (28) = −2.12, p = 0.038; mean difference −0.36 mm, 95% CI −0.70 to −0.03; Cohen’s d = −0.56). Supraspinatus tendinopathy was more prevalent in weight-training athletes (93.3% vs. 41.2%; OR 17.7, 95% CI 2.16–145.8; FDR-adjusted p = 0.003). Subscapularis tendinitis (40.0% vs. 17.6%; OR 3.58, 95% CI 1.00–12.88; FDR p = 0.14) and LHBT tenosynovitis (20.0% vs. 3.9%; OR 6.82, 95% CI 1.02–45.8; FDR p = 0.09) showed non-significant trends. Conclusions: Upper-limb weight training in young adults is associated with reduced AHD and a markedly higher prevalence of supraspinatus tendinopathy. Ultrasound proved valuable for early detection of structural and morphological alterations in shoulder soft tissues. Preventive strategies focusing on load management, exercise technique, and targeted strengthening should be prioritized. Full article

Background: Tibial pilon fractures are, in most cases, complex injuries caused by high-energy trauma. This type of fracture requires surgical stabilization and immobilization that impairs ankle function by reducing range of motion, muscle strength, and affecting the mechanical properties of the muscles. Methods: We evaluated 22 patients who required surgery for tibial pilon fractures and 22 age-matched healthy controls. Dynamometry assessed the isometric strength of the dorsiflexors and plantar flexors. Myotonometry of the tibialis anterior, peroneus longus, and medial and lateral gastrocnemius muscles analyzed the muscle tone, biomechanical (stiffness and decrement), and viscoelastic properties (mechanical stress relaxation and ratio of relaxation time to deformation time (creep). Results: Compared to the control group, the patients had significantly decreased isometric strength in both the dorsal flexors and plantar flexors on the affected side. Myotonometric measurements did not reveal significant differences in the tibialis anterior and peroneus longus muscles. Both medial and lateral gastrocnemius muscles exhibited significantly increased frequency and stiffness, and significantly decreased relaxation and creep in patients when compared to the control group. Conclusions: When compared to healthy controls, patients with surgically treated unilateral pilon fracture had a decreased isometric muscle force of ankle dorsiflexors and plantar flexors of both affected and non-affected lower limbs. Myotonometry indicated increased frequency and stiffness, along with decreased values of viscoelastic parameters (stress relaxation time and creep) in the medial and lateral gastrocnemius muscles on both sides. Full article

Prolonged operation of cotton picker poses significant risks of work-related musculoskeletal disorders (WMSDs), primarily driven by non-ergonomic cab layouts that fail to accommodate the unique “left-hand steering, right-hand lever” operational mode. Traditional optimization methods, relying on general digital human models or isolated surface electromyography (sEMG) measurements, often lack the physiological fidelity and computational efficiency for high-dimensional, personalized design. To address this interdisciplinary challenge in agricultural engineering and ergonomics, this study proposes a novel AMS-RF-DBO framework that integrates high-fidelity biomechanical simulation with intelligent optimization. A driver–cabin biomechanical model was developed using the AnyBody Modeling System (AMS) and validated against sEMG data (ICC = 0.695). This model generated a dataset linking cab layout parameters to maximum muscle activation (MA). Using steering wheel and control lever coordinates (X, Y, Z) as inputs, a Random Forest (RF) regression model demonstrated strong performance (R² = 0.91). Optimization with the Dung Beetle Optimizer (DBO) algorithm yielded an optimal configuration: steering wheel (L1 = 434 mm, H1 = 738 mm, θ = 32°) and control lever (L2 = 357 mm, H2 = 782 mm, M = 411 mm), reducing upper-limb MA from 3.82% to 1.47% and peak muscle load by 61.5%. This study not only provides empirical support for ergonomic cab design in cotton pickers to reduce operator fatigue and health risks but also establishes a replicable technical paradigm for ergonomic optimization of other specialized agricultural machinery. Full article

Background/Objectives: Accurate plantar pressure assessment is essential for injury prevention and rehabilitation monitoring in sports. Wearable sensor technologies, such as DAid^® Smart Socks, offer portable, real-time biomechanical feedback and enable data collection in field conditions. However, there is limited evidence on their level of agreement with a gold standard in measuring the foot plantar center of pressure (CoP) in football-specific tasks. This study aimed to determine the preliminary validity of DAid^® Smart Socks compared with a gold-standard force platform in measuring plantar center of pressure (CoP) during functional football FIFA 11+ Part 2 exercises. Methods: Ten male volunteer youth football players (mean age 12.2 ± 0.42 years; height 158.7 ± 7.72 cm; weight 46.46 ± 8.78 kg; shoe size EU 39.8 ± 2.68) from the Latvian Football Federation Youth League participated. Eight players had right-leg dominance, two had left-leg dominance; three reported past lower-limb injuries. Plantar pressure was measured simultaneously using DAid^® Smart Socks and a 1.5 m entry-level force platform with a calibration factor of 3.2. Center of pressure (CoP) data from the force platform were recorded using Footscan software version 9.10.4. Participants performed two selected FIFA 11+ Part 2 exercises—a single-leg squat (unilateral) and a squat with heel raise, performed bilaterally—under standardized conditions. Each exercise was performed twice, with sock removal and reapplication between trials. Agreement between the DAid^® Smart Socks and the force platform was examined using waveform synchronization, root mean square error (RMSE), Bland–Altman analysis, and Lin’s Concordance Correlation Coefficient (CCC) to quantify both relative waveform correspondence and absolute CoP measurement accuracy. Results: Across 160 paired recordings, the DAid^® Smart Socks showed moderate-to-high correlation with the force platform for relative CoP dynamics, with 79% of waveforms demonstrating CCC ≥ 0.60. Absolute agreement was limited, with only 16% of recordings reaching CCC ≥ 0.90, and RMSE values ranging from 2.1 to 18.9 mm (X) and 4.3–34.2 mm (Y). Conclusions: DAid^® Smart Socks showed moderate-to-high correspondence with the force platform in capturing the directional and temporal characteristics of plantar CoP during functional football tasks, with agreement varying across individuals. Full article