Search Results (367)

Background: This study aimed to examine the effects of an 8-week plyometric training program on lower-limb explosive strength, jump performance, musculotendinous stiffness, reactive strength index (RSI), and multidirectional speed in elite Polish badminton players. Methods: Twenty-four athletes were randomly assigned to either an experimental group (n = 15), which supplemented their regular badminton training with plyometric exercises, or a control group (n = 15), which continued standard technical training. Performance assessments included squat jump (SJ), countermovement jump (CMJ), single-leg jumps, sprint tests (5 m, 10 m), lateral movements, musculotendinous stiffness, and RSI measurements. Results: The experimental group showed statistically significant improvements in jump height, power output, stiffness, and 10 m sprint and lateral slide-step performance (p < 0.05), with large effect sizes. No significant changes were observed in the control group. Single-leg jump improvements suggested potential benefits for addressing lower-limb asymmetries. Conclusions: An 8-week plyometric intervention significantly enhanced lower-limb explosive performance and multidirectional movement capabilities in young badminton players. These findings support the integration of targeted plyometric training into regular training programs to optimize physical performance, improve movement efficiency, and potentially reduce injury risk in high-intensity racket sports. Full article

The mental and physical health of college students, especially in urban environments like Shanghai, is crucial given the high academic and urban stressors, which were intensified by the COVID-19 lockdown. Prior research has shown gender differences in health impacts during public health crises, with females often more vulnerable to mental health issues. Objective: This study aimed to comprehensively assess the physical and psychological health of Chinese college students post-lockdown, focusing on the relationship between stress, anxiety, depression, sleep patterns, and physical health, with a particular emphasis on gender differences. Methods: We conducted a cross-sectional study involving 116 students in Shanghai, utilizing psychological scales (HAMA, IPAQ, PSQI, SDS, FS 14, PSS, SF-36) and physical fitness tests (resting heart rate, blood pressure, hand grip, forced vital capacity, standing long jump, sit-and-reach, one-minute sit-up test and the one-minute squat test, single-leg stand test with eyes closed), to analyze health and behavior during the pandemic lockdown. All students have undergone the same life habits during the pandemic. Results: The HAMA scores indicated no significant levels of physical or mental anxiety. The PSS results (42.45 ± 8.93) reflected a high overall stress level. Furthermore, the PSQI scores (5.4 ± 2.91) suggested that the participants experienced mild insomnia. The IPAQ scores indicated higher levels of job-related activity (1261.49 ± 2144.58), transportation activity (1253.65 ± 987.57), walking intensity (1580.78 ± 1412.20), and moderate-intensity activity (1353.03 ± 1675.27) among college students following the lockdown. Hand grip strength (right) (p = 0.001), sit-and-reach test (p = 0.001), standing long jump (p = 0.001), and HAMA total score (p = 0.033) showed significant differences between males and females. Three principal components were identified in males: HAMA, FS14, and PSQI, explaining a total variance of 70.473%. Similarly, three principal components were extracted in females: HAMA, PSQI, and FS14, explaining a total variance of 69.100%. Conclusions: Our study underscores the complex interplay between physical activity (PA), mental health, and quality of life, emphasizing the need for gender-specific interventions. The persistent high stress, poor sleep quality, and reduced PA levels call for a reorganized teaching schedule to enhance student well-being without increasing academic pressure. Full article

Background: Anterior cruciate ligament reconstruction (ACLr) often leads to asymmetries between limbs, with variable return-to-performance rates in athletes. The single-leg countermovement jump (SLCMJ) is commonly used to assess postoperative knee function. However, limited research has explored deficits specifically during the unweighting phase of the jump. Methods: This study assessed 53 recreational athletes (11 females, 42 males) between 6 and 9 months post-ACLr using a dual force plate system (1000 Hz). Each participant performed three maximal-effort SLCMJs per limb. Outcome measures included jump height, negative peak velocity, minimum force, and center of mass (COM) displacement. Paired t-tests and Wilcoxon tests were used to compare the ACLr limb with the contralateral limb. Results: Compared to the healthy limb, the ACLr limb showed significantly lower negative peak velocity (−0.80 ± 0.40 m/s vs. −0.94 ± 0.40 m/s, p < 0.001), higher minimum force (36.75 ± 17.88 kg vs. 32.05 ± 17.25 kg, p < 0.001), and reduced COM displacement (−17.62 ± 6.25 cm vs. −19.73 ± 5.34 cm, p = 0.014). Eccentric phase duration did not differ significantly. Conclusions: Athletes post-ACLr demonstrate altered neuromuscular control during the early SLCMJ phase. These findings highlight the importance of rehabilitation strategies targeting eccentric strength and symmetry restoration. Full article

Driven by the rapid advancement of Vehicle-to-Grid (V2G) and Grid-to-Vehicle (G2V) technologies, improving power quality and system stability during charging and discharging has become a research focus. To address this, this paper proposes a Model Predictive Control (MPC) strategy for Active Neutral-Point Voltage Balancing (ANPVB) in a single-phase three-level converter used in on-board V2G chargers. Traditional converters rely on passive balancing using redundant vectors, which cannot ensure neutral-point (NP) voltage stability under sudden load changes or frequent power fluctuations. To solve this issue, an auxiliary leg is introduced into the converter topology to actively regulate the NP voltage. The proposed method avoids complex algorithm design and weighting factor tuning, simplifying control implementation while improving voltage balancing and dynamic response. The results show that the proposed Model Predictive Current Control-based ANPVB (MPCC-ANPVB) and Model Predictive Direct Power Control-based ANPVB (MPDPC-ANPVB) strategies maintain the NP voltage within ±0.7 V, achieve accurate power tracking within 50 ms, and reduce the total harmonic distortion of current (THDi) to below 1.89%. The proposed strategies are tested in both V2G and G2V modes, confirming improved power quality, better voltage balance, and enhanced dynamic response. Full article

Background: Current methods of postural control assessments and interventions to improve postural stability and thereby prevent falls often fail to incorporate the hazardous perturbation situations that frequently accompany falls. Virtual environments can safely incorporate these hazards. The purpose of the study was to identify if virtual slip and trip perturbations can be used as an exposure paradigm in place of real slip and trip perturbations to improve postural control. Methods: Fifteen healthy young adults were included in this study. Two paradigms, real gait exposure (real) and virtual environment gait exposure (virtual), consisting of real and virtual slip and trip trials, were performed by each participant in a counterbalanced order to avoid order effects. At baseline and following real and virtual paradigms, the modified clinical test for sensory integration and balance (mCTSIB), limits of stability (LOS), and single-leg stance (SLS) using BTracks balance plate were administered. Separate one-way (baseline vs. Real vs. Virtual) repeated measures analysis of variance were conducted on response variables. Results: In the posterior left quadrant of the LOS, significant differences were found after the real paradigm compared to baseline (p = 0.04). For the anterior left quadrant and total LOS, significant differences post real paradigm (p = 0.002 and p < 0.001) and virtual paradigm (p = 0.007 and p < 0.001) compared to baseline were observed. For the SLS, the left-leg significant differences were observed post real paradigm (p = 0.019) and virtual paradigm (p = 0.009) compared to BL in path length, while significant main effects were found for mean sway velocity for the left leg only (p = 0.004). For the right leg, significant differences were only observed after the virtual paradigm (p = 0.01) compared to BL. Conclusions: Both virtual and real paradigms were identified to improve postural control. The virtual paradigm led to increased postural control in the right-leg SLS condition, while the real paradigm did not, without any adverse effects. Findings suggest virtual reality perturbation exposure acutely improves postural control ability compared to baseline among healthy young adults. Full article

Background: Ischemic preconditioning (IPC) is a non-invasive, time-efficient strategy that has been shown to acutely enhance athletic performance. The present study examined the effects of 5 min of IPC on vertical and horizontal jump performance. A secondary aim was to explore the associations between outcomes of the 5-Hop (5-H) test and drop jump performance, in order to provide further evidence supporting the validity of the 5-H test for assessing reactive strength characteristics in trained jumpers. Methods: Twelve trained track and field jumpers (nine males, three females, age: 23.2 ± 2.9 years; height: 1.76 ± 0.07 m; body mass: 71.5 ± 8.0 kg) completed two conditions: an IPC condition applied to one leg and a control condition applied to the contralateral leg. In the first week, one leg was assigned to IPC and the other to the control condition, while in the second week, the conditions for each leg were reversed. Vertical single-leg performance was evaluated by drop jump (DJ) height, ground contact time, and reactive strength index (RSI). Horizontal jump performance was assessed by a five-hop (5-H) test during which total distance (TD), total time (TT), and reactive hopping index (RHI) were obtained. Results: Compared to the control condition, IPC enhanced DJ height (+ 3.6%) and RSI (+ 7.8%) (p < 0.05, g = 0.16 and 0.32, respectively) and reduced contact time (−4.4% p < 0.05, g = 0.41). Also, IPC resulted in significant improvements in TD (+ 4.1%) and RHI (+ 3.9%) during the 5-H test (p < 0.05, g = 0.32 and 0.42, respectively), while TT remained unchanged. Conclusions: A single cycle of IPC acutely improved vertical and horizontal jump performance and reactive strength indices in trained jumpers. These findings support the use of IPC as a practical, time-efficient method to enhance neuromuscular performance in explosive tasks. Full article

Background: The efficacy of postoperative exercise rehabilitation after spine surgery is controversial, and a protocol for exercise treatment and detailed outcomes based on functional activity have not yet been established. This study aimed to determine the efficacy of exercise rehabilitation after lumbar spine surgery. Methods: A prospective, randomized controlled trial was conducted in 40 patients who underwent lumbar spine surgery (20 patients each in the exercise and control groups) for 12 weeks. Clinical outcomes were assessed using the visual analog scale (VAS) for pain and EuroQol-5 Dimensions 5-Level version (EQ-5D-5L). Body proportions, including body mass index, total muscle mass, and body fat percentage were analyzed. Functional activity was evaluated based on the range of motion of the lumbar spine, strength and endurance of lumbar flexion/extension, flexibility, 6 min walking test, single-leg stance, coordination, and gait pattern analysis. Results: The exercise group showed significantly greater improvement in VAS for pain (66.67% versus 20.00%, p < 0.001) and EQ-5D-5L (45.56% versus 20.00, p = 0.039) compared to the control group. Serial assessment revealed significant improvement in strength of lumbar flexion/extension, 6 min walking test, single-leg stance, coordination, and gait patterns in the exercise group compared to the control group. In particular, the single-leg stance time for the affected leg improved more markedly in the exercise group (280.9% versus 48.7%, p < 0.001). Conclusion: Tailored postoperative exercise after lumbar spine surgery is effective in reducing pain and enhancing functional recovery, including strength and balance. Full article

Background/Objectives: Power indices may provide valuable information for performance and injury prevention in soccer players, so increasing the knowledge about them seems essential. Therefore, this study aimed to establish limb-specific normative values for flywheel-derived power indices in professional soccer players, while accounting for limb performance or ability, to explore the relationships between power indices across variables and to compare the power outcomes related to these indices between injured and non-injured players within four months post-assessment. Methods: Twenty-two male professional soccer players (age: 26.6 ± 4.6 years; competitive level: Belgian second division) were recruited from a single elite-tier club to participate in this cross-sectional diagnostic study. Participants underwent a standardized assessment protocol, executed in a rotational inertial device, comprising six unilateral exercises focused on the lower limbs: hip-dominant quadriceps (Qhip), knee-dominant quadriceps (Qknee), hip-dominant hamstrings (Hhip), knee-dominant hamstrings (Hknee), adductor (Add), and abductor (Abd). The testing session incorporated a randomized, counterbalanced design, with each exercise comprising two sets of eight maximal concentric–eccentric repetitions per limb. Leg dominance was operationally defined as the self-reported preferred limb for ball-striking tasks. Power indices were calculated from these exercises. Results: No significant differences in flywheel-derived power indices were found between limbs or between injured and non-injured players. However, significant correlations between indices were found in all power variables, with the Qhip:Qknee and Hhip:Hknee concentric ratios emerging as the most clinically actionable biomarkers for rapid screening. Conclusions: These results suggest the necessity of including more variables for injury prediction. Moreover, power indices could be considered based on the classification of limbs as “strong” or “weak”. Full article

Background: Core stability is a cornerstone of optimum athletic performance, and its reduction is a risk factor for athletic injuries. Evidence has shown that core impairments can alter lower-limb mechanics through the kinetic chains. Additionally, plantar pressure can be influenced by proximal conditions, such as core muscle fatigue. Therefore, this study aimed to investigate the correlation between core endurance and plantar pressure distribution (PPD) during double-leg stance, single-leg stance, and single-leg squat positions in healthy male athletes. Methods: A total of 21 healthy male recreational athletes between 19 and 26 years of age volunteered to participate in this correlational study. The McGill core endurance test was used to measure the endurance of their core flexors, extensors, and lateral flexors. The participants’ PPD was evaluated using the Tekscan Mobile Mat pressure measurement system in three positions (double-leg stance, single-leg stance, and single-leg squat) for both the dominant and non-dominant feet. Results: There was a poor and insignificant correlation (p > 0.05) between the core flexors’, extensors’, and side flexors’ endurance and the peak and total PPD in all the tested positions for both the dominant and non-dominant feet. Conclusions: Core muscle endurance is neither a component that affects nor is affected by the PPD in this study population. Thus, the endurance of core flexors, extensors, and side flexors may not be considered in screening, examination, or intervention for the total and peak pressure during double-leg stance, single-leg stance, and single-leg squat positions for both the dominant and non-dominant feet in the study population. Further similar studies are warranted in various sports and during dynamic tasks to better understand the different dimensions of the studied relationship in athletes. Full article

Background/Objectives: Despite extensive research on caffeine’s (CAF’s) ergogenic effects, evidence regarding its impact on anaerobic performance in female athletes remains limited and inconclusive. The aim of this study was to investigate the acute effects of 6 mg/kg⁻¹ caffeine on anaerobic performance, functional strength, agility, and ball speed in female soccer players. Methods: A randomized, double-blind, placebo-controlled crossover design was employed. Thirteen moderately trained female soccer players (age: 21.08 ± 1.11 years; height: 161.69 ± 6.30 cm; weight: 59.69 ± 10.52 kg; body mass index (BMI): 22.77 ± 3.50 kg/m²; training age: 7.77 ± 1.16 years; habitual caffeine intake: 319 ± 160 mg/day) completed two experimental trials (caffeine vs. placebo (PLA)), separated by at least 48 h. Testing sessions included performance assessments in vertical jump (VJ), running-based anaerobic sprint test (RAST), bilateral leg strength (LS), handgrip strength (HS), single hop for distance (SH), medial rotation (90°) hop for distance (MRH), change of direction (COD), and ball speed. Rating of perceived exertion (RPE) was also recorded. Results: CAF ingestion significantly improved minimum (p = 0.011; d = 0.35) and average power (p = 0.007; d = 0.29) during RAST. A significant increase was also observed in SHR (single leg hop for distance right) performance (p = 0.045; d = 0.44). No significant differences were found in VJ, COD, ball speed, LS, HS, SHL, MRHR, or MRHL (p > 0.05). RPE showed a moderate effect size (d = 0.65) favoring the CAF condition, though not statistically significant (p = 0.110). Conclusions: In conclusion, acute CAF intake at a dose of 6 mg/kg⁻¹ may enhance anaerobic capacity and lower-limb functional strength in female soccer players, with no significant effects on jump height, agility, or upper-body strength. Full article

The purpose of this study was to determine the effect of static stretching (SS) duration on balance. Twenty-two participants performed passive dorsiflexion measurements and balance tests before and after SS. Passive dorsiflexion measurements determined the maximal dorsiflexion angle, passive torque, displacement of the muscle–tendon junction, and electromyography amplitude during passive dorsiflexion. In the balance test, the participant stood on a single leg with their eyes open while the postural sway evaluated in the center of pressure (COP), standing duration, and electromyography amplitude were measured. The ankle and metatarsophalangeal joints underwent SS for 30 s × one set, two sets, and four sets. There were significant increases in COP displacement and COP velocity after two sets of SS but not after one and four sets. Standing duration and electromyography during balance tests were not changed after SS. No gender differences were found in changes in balance. Maximal dorsiflexion angle and passive torque were increased after SS, but the displacement of the muscle–tendon junction and electromyography during passive dorsiflexion were not changed. There was no significant correlation between changes in maximal dorsiflexion angle or passive torque and changes in COP variables after two sets of SS. These results therefore revealed that SS duration affects COP displacement and COP velocity. Full article

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

Biological systems can adaptively navigate multi-terrain environments via morphological and behavioral flexibility. While robotic systems increasingly achieve locomotion versatility in one or two domains, integrating terrestrial, aquatic, and aerial mobility into a single platform remains an engineering challenge. This work tackles this by introducing a bipedal robot equipped with a reconfigurable locomotion framework, enabling seven adaptive policies: (1) thrust-assisted jumping, (2) legged crawling, (3) balanced wheeling, (4) tricycle wheeling, (5) paddling-based swimming, (6) air-propelled drifting, and (7) quadcopter flight. Field experiments and indoor statistical tests validated these capabilities. The robot achieved a 3.7-m vertical jump via thrust forces counteracting gravitational forces. A unified paddling mechanism enabled seamless transitions between crawling and swimming modes, allowing amphibious mobility in transitional environments such as riverbanks. The crawling mode demonstrated the traversal on uneven substrates (e.g., medium-density grassland, soft sand, and cobblestones) while generating sufficient push forces for object transport. In contrast, wheeling modes prioritize speed and efficiency on flat terrain. The aquatic locomotion was validated through trials in static water, an open river, and a narrow stream. The flight mode was investigated with the assistance of the jumping mechanism. By bridging terrestrial, aquatic, and aerial locomotion, this platform may have the potential for search-and-rescue and environmental monitoring applications. Full article

(1) Background: When implementing new biomechanical and technology-based assessments, such as the jump assessment in Multiple Sclerosis (MS), into clinical routine, it is important to ensure that they are based on the real needs of patients and to identify and adapt to potential barriers early on. (2) Methods: In the present cross-sectional study, 157 pwMS performed a sensor-based jump assessment on a force plate consisting of three jump tests: 10 s jump test (10SHT), countermovement jumps (CMJ), and single-leg countermovement jumps (SLCMJ). After the jump assessment, the patient experience measures (PREM) were recorded using a paper-based questionnaire on an 11-point scale from 0 (positive) to 10 (negative). (3) Results: PwMS showed an overall positive experience with the sensor-based jump assessment. “Staff support performance”, “acceptance required time”, “usefulness” of the results, and “integration of results in therapy” were the best rated items with a median of 0 (positive). The CMJ was perceived as the easy (p < 0.05) and less exhausting (p < 0.05). PwMS who experienced CMJ as easy, not exhausting, and safe were associated with higher CMJ performance, especially in peak power, flight time, and jump height (r > −0.4). Significant associations were found between PREMs and age, sex, BMI, physical activity, and disability degree. (4) Conclusions: The study findings support the feasibility of jump assessment in clinical practice and highlight the need for patient-centered integration of innovative technologies to optimize precision neuromuscular function evaluation in MS. Full article

Background and Objectives: Low back pain (LBP) is a leading cause of disability worldwide. Core stabilization exercises such as the plank are often prescribed in rehabilitation settlings to improve neuromuscular control and spinal support. However, it remains unclear whether plank performance -accurately reflects trunk function or disability in individuals with LBP. The purpose of this study was to evaluate the relationship between plank endurance and low back pain in adults. Methods: A cross-sectional study was conducted with 117 adults aged 20–61 years (mean 26.0 ± 9.3), including both individuals with and without LBP. Participants completed a plank endurance test and the Modified Oswestry Disability Index (MODI). A subset of fifty-four participants with LBP also completed single-leg bridge tests to assess posterior chain endurance. Statistical analyses included Mann–Whitney U tests to compare plank times by LBP status, logistic regression to evaluate predictors of LBP, and correlation analyses to examine associations between the bridge-to-plank ratio and MODI scores. Results: Contrary to the initial hypothesis, individuals with LBP demonstrated significantly longer plank hold times than those without (U = 1861.00, p = 0.036). Logistic regression indicated that the overall model was statistically significant (χ² = 12.39, p = 0.030), but plank duration was not an independent predictor of LBP (p = 0.070). Among participants with LBP, a higher bridge-to-plank ratio, reflecting relatively greater posterior chain endurance, was significantly associated with lower disability scores (Pearson r = −0.31, p = 0.023; Spearman ρ = −0.32, p = 0.018). Conclusions: These findings suggest that, while plank duration differs by LBP status, longer plank times may not indicate lower risk or severity of back pain. A greater balance of posterior chain to anterior core endurance may be more intricately linked to reduced disability, highlighting the importance of comprehensive core assessment and training strategies in rehabilitation. Full article