Search Results (74)

This paper addresses inherent limitations in unmanned aerial vehicle (UAV) undercarriages hindering vertical takeoff and landing (VTOL) capabilities on uneven slopes and obstacles. Robotic landing gear (RLG) designs have been proposed to address these limitations; however, existing designs are typically limited to ground slopes of 6–15°, beyond which rollover would happen. Moreover, articulated RLG concepts come with added complexity and weight penalties due to multiple drivetrain components. Previous research has highlighted that even a minor 3-degree slope change can increase the dynamic rollover risks by 40%. Therefore, the design optimization of robotic landing gear for enhanced VTOL capabilities requires a multidisciplinary framework that integrates static analysis, dynamic simulation, and control strategies for operations on complex terrain. This paper presents a novel, hybrid, compliant, belt-driven, three-legged RLG system, supported by a multidisciplinary design optimization (MDO) methodology, aimed at achieving enhanced VTOL capabilities on uneven surfaces and moving platforms like ship decks. The proposed system design utilizes compliant mechanisms featuring a series of three-flexure hinges (3SFH), to reduce the number of articulated drivetrain components and actuators. This results in a lower system weight, improved energy efficiency, and enhanced durability, compared to earlier fully actuated, articulated, four-legged, two-jointed designs. Additionally, the compliant belt-driven actuation mitigates issues such as backlash, wear, and high maintenance, while enabling smoother torque transfer and improved vibration damping relative to earlier three-legged cable-driven four-bar link RLG systems. The use of lightweight yet strong materials—aluminum and titanium—enables the legs to bend 19 and 26.57°, respectively, without failure. An animated simulation of full-contact landing tests, performed using a proportional-derivative (PD) controller and ship deck motion input, validate the performance of the design. Simulations are performed for a VTOL UAV, with two flexible legs made of aluminum, incorporating circular flexure hinges, and a passive third one positioned at the tail. The simulation results confirm stable landings with a 2 s settling time and only 2.29° of overshoot, well within the FAA-recommended maximum roll angle of 2.9°. Compared to the single-revolute (1R) model, the implementation of the optimal 3R Pseudo-Rigid-Body Model (PRBM) further improves accuracy by achieving a maximum tip deflection error of only 1.2%. It is anticipated that the proposed hybrid design would also offer improved durability and ease of maintenance, thereby enhancing functionality and safety in comparison with existing robotic landing gear systems. Full article

Background: Participation in on-duty exercise is critical to enhance firefighter safety and readiness. However, these sessions are often interrupted with emergency responses and require firefighters to work in a fatigued state that may increase injury risk. Objective: To assess the impact of on-duty resistance training on neuromuscular function. Methods: A sample of 18 firefighters (Age: 38.8 ± 8.0 y; Body fat: 24.9 ± 7.0%) completed three testing sessions, separated by at least 72 h to compare the effects of circuit (CT) versus heavy resistance training (HRT) fatigue on neuromuscular function. During Session 1, anthropometrics and familiarization trials of balance and neuromuscular function were completed, which included single-leg drop landing (SLDL), postural sway (PS), and modified Functional Balance Test (mFBT). Sessions 2 and 3 were randomized, where participants completed either HRT or CT. Isometric midthigh pull (IMTP), long jump (LJ), and lower body power (LBP) tests were conducted pre- and immediately post exercise, whereas static and dynamic balance assessments were conducted pre- and 10 min post exercise to simulate an emergency response time course. Repeated measures ANOVA, effect sizes, and difference scores were used to analyze the effects of condition and time. The level of significance was set at p < 0.05. Results: CT decreased IMTP, LJ, and LBP, whereas HRT decreased LJ and LBP (p ≤ 0.001, ES ≥ 0.476). Despite several significant condition by time interaction effects on balance outcomes, there were no differences within CT or HRT over time (p ≥ 0.066). Conclusions: These findings suggest that on-duty resistance training reduces firefighters’ power and/or strength immediately post exercise but does not influence most firefighters’ balance 10 min post exercise. Thus, firefighters are recommended to perform resistance training on-duty during low emergency call volume times. Full article

The knee is a complex joint essential for locomotion, providing stability that is crucial for avoiding biomechanical deviations such as dynamic knee valgus (DKV), a contributing injury risk factor. This study aimed to assess the influence of body mass index (BMI), age, sex, anthropometric variables, visual feedback, and drop height on the occurrence of DKV. Forty healthy adults aged between 18 and 45 years, with a BMI between 18.5–29.9 kg/m² and no lower limb injuries, were evaluated. Participants underwent a standardized warm-up, anthropometric measurements, and a single-leg drop-landing test from 20 to 30 cm, with and without visual feedback. Women exhibited significantly higher DKV in nearly all conditions. Statistically significant differences were observed between legs when no feedback was provided. Visual feedback significantly reduced DKV in one condition (left limb at 30 cm). Significant weak negative correlations with DKV were found for age, BMI, thigh length, and leg length. These data suggest that women may have higher DKV, anatomical variables may be associated with DKV, and visual feedback may have the potential to attenuate its occurrence. These findings highlight the importance of targeted interventions to attenuate DKV and underscore the role of body awareness and feedback in improving knee alignment. Full article

Background/Objectives: Adolescent female basketball players are frequently affected by lateral ankle sprains that may progress to chronic ankle instability (CAI) if not adequately managed. This double-blind, prospective, cluster-randomized controlled trial aimed to compare the effects of hop-stabilization training (hop training) and those of traditional balance training on ankle instability and functional performance of this population. Methods: Thirty-two adolescent female basketball players with CAI were cluster-randomized into the hop training group (HG; n = 16) or balance training group (BG; n = 16). Participants completed three 20 min sessions per week for 6 weeks. The hop training protocol comprised multiplanar hopping exercises with progressive increases in the landing volume and an emphasis on controlled landing mechanics. The balance training protocol included single-leg stance and basketball-specific dynamic activities with gradually increasing difficulty. Primary outcomes were self-reported ankle stability (Cumberland ankle instability tool [CAIT] score) and performance test results (t-test, lateral hop test, figure-8 hop test results). Secondary outcomes included static and dynamic balance and isometric ankle strength (dorsiflexion [DF], plantar flexion, inversion, eversion [EV]). Assessments were conducted at baseline and after interventions. Results: The HG and BG exhibited significant improvements in CAIT scores and balance. However, the HG demonstrated significantly greater enhancements in dynamic performance test results and notable improvements in DF and EV strength compared to those of the BG. Conclusions: Hop training comprising the close replication of the multidirectional and dynamic demands of basketball was more effective than traditional balance training for enhancing functional performance and ankle strength. Full article

Background/Objectives: Kinematic measurements obtained from functional tests have been used to identify associated and risk factors for the development of lower limb dysfunction, allowing targeted interventions to reduce potential risks and guide rehabilitation. It is necessary to identify variables and tests with adequate reliability and with the capability to discriminate individuals with and without lower limb functional deficits. This study aimed to determine which single-legged test (single-leg squat and single-leg landing) and variables (angle at deepest instant and range of motion) present the best reliability and capability to discriminate individuals with and without lower limb functional deficits. Methods: The frontal plane kinematics of 86 adults, divided into 2 groups (43 with lower limb functional deficits and 43 without), as classified by the Lower Extremity Functional Scale, were assessed during single-leg squat and single-leg landing tasks. The differences between groups in trunk, pelvis, hip, and knee ranges of motion and angles were tested using the independent T test or Mann–Whitney U test, and the test–retest, inter-rater, and intra-rater absolute (standard error of measurement and minimal detectable difference) and relative (intraclass correlation coefficient) reliability were calculated. Results: Trunk (r = 0.47), hip (r = 0.40), and knee (r = 0.35) angles at the deepest instant, as well as range of motion of the trunk (r = 0.33), pelvis (r = 0.47), and knee (r = 0.32) during the single-leg landing discriminated between groups (p < 0.05). For the single-leg squat, no variable discriminated the groups. Test–retest, inter-rater, and intra-rater reliability ranged from poor to excellent, with minimal detectable differences remaining below 19°. Conclusions: The single-leg landing and pelvis range of motion were the most effective tests and variables for discriminating individuals with and without lower limb functional deficits. Most variables demonstrated moderate test–retest and excellent inter-rater and intra-rater reliability. Full article

Anterior cruciate ligament (ACL) injuries can occur in non-contact conditions (e.g., jump-landing) and are common among junior badminton players. The knee abduction angle has been widely identified as a biomechanical risk factor that likely contributes to this injury mechanism. Purpose: This study aims to examine the relationship between the trunk and lower limb landing kinematics and the peak knee abduction angle following a jumping smash. Method: Twenty-one male junior badminton players performed jump smashes on an instrumented badminton court. Anthropometry was measured; trunk and lower limb single-leg landing kinematics and kinetics were collected using a motion capture system. Pearson’s correlation was performed to identify the variables significantly correlated to peak knee abduction angle, followed by stepwise multiple regression to identify the most important combination of predictors. Results: Regression analysis showed that knee external rotation angle at foot contact and peak knee internal rotation angle were associated with peak knee abduction angle. A separate analysis also showed that landing time was positively associated with peak knee abduction angle. Conclusions: Assessing ACL injury risk and developing injury prevention strategies for jump landings in badminton should focus on knee motion in the frontal and transverse planes, as well as landing time. Full article

Purpose: This study aimed to evaluate neuromuscular control and muscle activation patterns in individuals following anterior cruciate ligament (ACL) reconstruction, compared to healthy controls. Methods: A cross-sectional comparative study was conducted following STROBE guidelines, including 16 participants (ACL group: n = 9; control group: n = 7). Participants performed the single-leg squat (SLS) test and the single-leg drop landing (SLDL) test. Neuromuscular control was assessed using the Qualitative Analysis of Single-Leg Loading Score (QASLS), while gluteus medius and vastus medialis activation were recorded using surface electromyography. Results: The ACL group showed significantly higher QASLSs in the SLS test (p = 0.0113), indicating poorer movement quality, while no difference was found in the SLDL test (p = 0.5484). Gluteus medius activation was lower in the ACL group during the SLS test (p = 0.0564), and vastus medialis activation was higher but not significantly different (p = 0.095). Conclusions: These findings highlight persistent neuromuscular deficits post-ACL-reconstruction, particularly in SLS tasks, reinforcing the need for targeted rehabilitation strategies focusing on hip stabilization and quadriceps motor control to optimize movement quality and reduce reinjury risk. Full article

Limited research has explored the impact of balance training on young alpine skiers, despite its recognized importance in the sport. This study evaluated the effects of a 10-week dry-land balance training program on the balance and skiing technique of skiers aged 9–11 years. The program employed five training modalities: neuromuscular, plyometric, core stability, proprioceptive, and equipment-based balance training. Thirty participants were divided into experimental and control groups based on their initial SKI IQ scores. The assessments included static balance (BTS P-Walk), explosive power (BTS G-Walk), and on-snow metrics (SKI IQ; balance, pressure, and edging) using CARV technology. The statistical analysis revealed significant improvements in the experimental group for the SKI IQ (F = 13.239; p = 0.001; η² = 0.321) in terms of the balance metric (F = 4.800; p = 0.037) and pressure metric (F = 8.084; p = 0.008), and for the static balance parameters, such as mediolateral stability in a two-legged stance (F = 4.304; p = 0.047; η² = 0.133) and anteroposterior stability in eyes-closed conditions (F = 14.249; p = 0.001; η² = 0.337). The single-leg stance stability and explosive force (F = 6.08; p = 0.02) also showed marked enhancements. The edging performance, however, showed no significant change. This study underscores the value of balance training for enhancing young skiers’ performance metrics and highlights wearable technology as an effective tool for real-time feedback. Integrating balance-focused programs into alpine skiing preparation can boost performance. Full article

Background/Objectives: Football poses a high risk of sustaining lower-limb injuries, particularly anterior cruciate ligament (ACL) injuries, owing to the frequent jumping and landing movements. Identifying risk factors for these injuries is crucial to successful prevention. Two-dimensional (2D) video analysis is a commonly employed tool for assessing movement patterns and determining injury risk in clinical settings. This study aims to investigate whether variations in the camera frame rate impact the accuracy of key angle measurements (knee valgus, hip adduction (HADD), and lateral trunk flexion (LTF)) in male football players during high-risk functional tasks such as single-leg landing and 45° side-cutting. Methods: This laboratory-based cross-sectional study included 29 football players (mean (SD) age: 24.37 [3.14] years). The frontal plane projection angle (FPPA), HADD, and LTF during single-leg landing and side-cutting tasks were measured using two different camera frame rates: 30 frames per second (fps) and 120 fps. The 2D kinematic data were analyzed using Quintic Biomechanics software. Results: Significant differences in FPPA scores during single-leg landing were observed between the 30 fps and 120 fps for both the dominant (mean difference = 2.65 [95% confidence interval [CI]: 0.76–4.55], p = 0.008) and non-dominant leg (3.53 [1.53–5.54], p = 0.001). Additionally, the FPPA of the right leg during the side-cutting task showed significant differences (2.18 [0.43–3.93], p = 0.016). The LTF of the right leg during side-cutting displayed a significant variation between frame rates (−2.69 [−5.17–−0.22], p = 0.034). No significant differences in HADD were observed. Conclusions: Compared with a 30 fps camera, a high-speed (120 fps) camera demonstrated a superior performance in delivering accurate kinematic assessments of lower-limb injury risk factors. This improved precision supports injury screening, rehabilitation monitoring, and return-to-play decision-making through determining subtle biomechanical deficits crucial for lower-limb injury prevention and management. Full article

Background/Objectives: This study compared step-by-step kinematic measurements from an infrared contact mat (IR-mat) and an inertial measurement unit (IMU) system during bounding and single leg jumping for speed, while also evaluating the validity of algorithms originally developed for sprinting and running when applied to horizontal jumps. The aim was to investigate differences in contact times between the systems. Methods: Nineteen female football players (15 ± 0.5 years, 61.0 ± 5.9 kg, 1.70 ± 0.06 m) performed attempts in both jumps over 20 m with maximum speed, of which the first eight steps were analysed. Results: Significant differences were found between the systems, with the IR-mat recording longer contact times than the IMU. The IR-mat began and ended its measurements slightly earlier and later, respectively, compared to the IMU system, likely due to the IMU’s algorithm, which was developed for sprinting with forefoot contact, while more midfoot and heel landing is used during jumps. Conclusions: Both systems provide reliable measurements; however, the IR mat consistently records slightly longer contact times for horizontal jumps. While the IMU is dependable, it exhibits a consistent bias compared to the IR mat. For bounding, the IR mat begins recording 0.018 s earlier at touch down and stops 0.021 s later. For single leg jumps, it starts 0.024 s earlier and ends 0.021 s later, resulting in contact times that are, on average, 0.039–0.045 s longer. These findings provide valuable insights for coaches and researchers in selecting appropriate measurement tools, highlighting the systematic differences between IR mats and IMUs in horizontal jump analysis. Full article

The purpose of this study was to clarify the relationship between vertical ground reaction force (VGRF) and acceleration from wearable inertial measurement units (IMUs) during single-leg drop landing after anterior cruciate ligament reconstruction (ACLR). Twenty-six participants, 42.4 ± 5.3 weeks after ACLR, performed three single-leg drop landing trials bilaterally. The peak VGRF was assessed using a force plate. The resultant acceleration was calculated using IMUs attached to the shank, thigh, and lumbar region. Univariate regression analysis was performed to examine the linear relationship between the VGRF and resultant acceleration. The limb symmetry index (LSI) of the VGRF was linearly associated with the LSI of the resultant accelerations at the shank, thigh, and lumbar sensors (R² = 0.166, p = 0.039; R² = 0.525, p < 0.001; and R² = 0.250, p = 0.009, respectively). In the involved limb, only the resultant acceleration at the thigh was a significant predictor of VGRF (R² = 0.490, p < 0.001), whereas in the uninvolved limb, the resultant accelerations at the shank, thigh, and lumbar sensors were significant predictors of VGRF (R² = 0.245, p = 0.010; R² = 0.684, p < 0.001; and R² = 0.412, p < 0.001, respectively). Caution may be required when using IMUs to predict VGRF asymmetry because the coefficient of determination for predicting VGRF is lower in the involved limb than in the uninvolved limb. Full article

Quadruped robots, with their biomimetic structure, are capable of stable locomotion in complex terrains and are vital in rescue, exploration, and military applications. However, developing multi-modal robots that feature simple motion control while adapting to diverse amphibious environments remains a significant challenge. These robots need to excel at obstacle-crossing, waterproofing, and maintaining stability across various locomotion modes. To address these challenges, this paper introduces a novel leg–fin integrated propulsion mechanism for a bionic quadruped robot, utilizing rapidly advancing soft materials and integrated molding technologies. The robot’s motion is modeled and decomposed using an improved central pattern generator (CPG) control network. By leveraging the control characteristics of the CPG model, global control of the single-degree-of-freedom drive mechanism is achieved, allowing smooth transitions between different motion modes. The design is verified through simulations conducted in the Webots environment. Finally, a physical prototype of the quadruped compliant robot is constructed, and experiments are carried out to test its walking, turning, and obstacle-crossing abilities in various environments. The experimental results demonstrate that the robot shows a significant speed advantage in regions where land and water meet, reaching a maximum speed of 1.03 body lengths per second (bl/s). Full article

Background/Objectives: After anterior cruciate ligament reconstruction (ACLR), a 6-month composite test is recommended during rehabilitation before the return to sport, and the influence of a meniscal tear is not known. The hypothesis was that the location and treatment of meniscus injuries could influence the results of the composite test. Methods: A retrospective single-center study was carried out of prospectively collected data involving 504 patients who performed a composite test 6 months after ACLR. Isolated ACLR was compared to ACLR with medial meniscus injuries (MM), lateral meniscus injuries (LM), and bimeniscal injuries (BM) using a composite test including a single-leg squat (SLS), a single-leg landing (SLL), a single hop for distance (SHD), a triple hop for distance (THD) and a side-hop test (Side-HT), isokinetic strength tests, and an assessment of the anterior cruciate ligament—return to sport after injury (ACL-RSI). Results: Compared with isolated ACLR, MM injury was associated with a quadricipital deficit at a velocity of 240°/s (14% ± 14% vs. 18% ± 18%, p = 0.02), hamstring deficit at 30°/s (14% ± 18% vs. 18% ± 18%, p = 0.02) and an increase in the hamstring/quadricipital ratio at 240°/s (68% ± 27% vs. 80% ± 67% p = 0.02). Furthermore, ACLR + MM or ML injuries in the operated knee generated an increase in the dynamic valgus frequency detected by the SLS, respectively (40% ± 49% vs. 51% ± 50%, p = 0. 05) and (40% ± 49% vs. 54% ± 50%, p = 0.02). Meniscal repair and meniscectomies showed no differences. Conclusions: These results show that meniscal injuries lead to muscle imbalance for MM injuries and impaired neuromuscular control for MM and LM injuries and suggest that meniscal repairs should be done. Moreover, rehabilitation must be adapted to meniscus injuries. Full article

This study aimed to evaluate the biomechanics of single-leg drop landing in individuals with functional ankle instability (FAI) during cognitive tasks, contrasting these findings with those of healthy controls to provide insights for evidence-based rehabilitation strategies. Fifteen FAI participants, identified using clinical tools, were age- and activity-matched with controls. They performed drop landings with and without a cognitive task, and the data were analyzed using a 2 × 2 mixed ANOVA. At the initial ground contact (IC), the FAI group’s affected side showed a significantly smaller plantarflexion angle than the control group (p = 0.008). With cognitive tasks, this angle increased in the FAI group (p = 0.005). The FAI group also had larger knee flexion at contact (p = 0.002) and greater knee valgus at peak vertical ground reaction force (vGRF) (p = 0.027). They exhibited a higher peak vGRF, shorter time to peak vGRF (T-vGRF), and higher loading rate (LR) (all p < 0.05). No differences were found in other variables (p > 0.05). This study shows that FAI individuals make specific biomechanical adjustments under cognitive tasks, notably increased plantarflexion at IC, suggesting reactive compensations. Despite similar motor control to controls, this may reflect long-term adaptations rather than equal proficiency. Full article

(1) Background: This study investigated the impact of different footwear conditions on the biomechanics of individuals with Functional Ankle Instability (FAI) during single-leg drop landing movements. (2) Methods: Fifteen participants with FAI and a control group were tested. Kinematics and kinetics were measured using Vicon (Model: MX13, Oxford, UK) and Kistler (Model: 9287B, Switzerland) equipment. A mixed-ANOVA analyzed the impact of footwear conditions. (3) Results: At the initial contact (IC), under the shoe-wearing condition, the FAI group exhibited a significantly smaller ankle-joint plantarflexion angle compared to the control group (p = 0.001). The FAI group exhibited a significantly smaller ankle-joint plantarflexion angle under the shoe-wearing condition compared to the barefoot condition at the IC (p < 0.001). At the IC moment, regardless of the footwear conditions in this study, the FAI group showed a larger knee flexion angle (p = 0.028) and a shorter time to vertical ground reaction force (T_vGRF) (p = 0.020) compared to the control group. (4) Conclusions: The study concluded that footwear conditions significantly influence the biomechanics of FAI individuals, with shoes enhancing ankle stability and barefoot conditions leading to biomechanics similar to healthy individuals. The effect of socks on FAI individuals was not significant. Future research should further explore the impact of footwear on FAI rehabilitation. Full article