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Context: Analyzing flick movement kinematics biomechanically is important to prevent sport-related injuries in underwater hockey players since the aquatic-based flick movement is completely different from land-based flick movements. The study aimed to describe the flick movement kinematic biomechanically in underwater hockey players. Moreover, this study further aimed to investigate the effect of the Thrower's Ten exercises on flick movement kinematics in underwater hockey players. Design: Descriptive laboratory study. Methods: Seventeen underwater hockey players (age: 26.2 [4.3] y; sports age: 6.2 [4.5] y) were included. First, 2 underwater cameras using motion capture video analysis MATLAB were used to biomechanically analyze the angular changes on the shoulder, elbow, wrist, and body while players were performing the flick movements. Players were then recruited to the Thrower's Ten exercise program for 6 weeks. Flick movement kinematics and flick-throwing distance were recorded at baseline and 6 weeks. Results: The flick movement kinematic patterns demonstrated increased shoulder flexion (from 102.5° to 144.9°), wrist extension (from 9.5° to 10.8°), and upper-extremity rotation (from 5.7° to 56.8°) while decreased elbow extension (from 107.7° to 159.2°) from the stick met the puck until the competition of the movement. The Thrower's Ten exercises improved the elbow extension (P =.04), wrist extension (P =.01), body rotation (P <.001), and flick-throwing distance (P <.001) from baseline to 6 weeks. Conclusion: This study describes the underwater flick kinematic technique biomechanically and interprets preliminary findings for the first time. Thus, 6 weeks of Thrower's Ten exercise program provides more body muscle movements than the smaller ones during the flick movements and higher flick-throwing distance in underwater hockey players. [ABSTRACT FROM AUTHOR]

Context: The best current evidence supports the effectiveness of neuromuscular training in reducing the risk of injury; however, the rate of anterior cruciate ligament (ACL) injuries is still high. Neurocognitive training (NT) has successfully improved biomechanical risk factors, but they have been considered in only a few studies. Objective: To review the literature to determine the effect of NT on biomechanical risk factors related to ACL injury in athletes. Evidence Acquisition: We searched PubMed, Google Scholar, Scopus, Science Direct, and the Physiotherapy Evidence Database from inception to August 2011. We included randomized controlled trials that used motor learning approaches and injury prevention programs to investigate kinematic and kinetic risk factors related to ACL injury. The quality of each clinical trial study was evaluated by the Physiotherapy Evidence Database scale. The eligibility criteria were checked based on the PICOS (population, intervention, comparison, outcome, and study type) framework. Evidence Synthesis: A total of 9 studies were included in the final analysis. Motor learning approaches include internal and external focus of attention, dual tasks, visual motor training, self-control feedback, differential learning, and linear and nonlinear pedagogy, combined with exercise programs. In most of the studies that used NT, a significant decrease in knee valgus; tibial abduction and external rotation; ground reaction force; and an increase in knee-, trunk-, hip-, and knee-flexion moment was observed. Conclusion: In classical NT, deviation from the ideal movement pattern especially emphasizing variability and self-discovery processes is functional in injury prevention and may mitigate biomechanical risk factors of ACL injuries in athletes. Practitioners are advised to use sport-specific cognitive tasks in combination with neuromuscular training to simulate loads of the competitive environment. This may improve ACL injury risk reduction and rehabilitation programs. [ABSTRACT FROM AUTHOR]

Purpose: Performing back squats with elastic bands has been widely used in resistance training. Although research demonstrated greater training effects obtained from adding elastic bands to the back squat, little is known regarding the optimal elastic resistance and how it affects neuromuscular performance. This study aimed to compare the force, velocity, power, and muscle activity during back squats with different contributions of elastic resistance. Methods: Thirteen basketball players performed 3 repetitions of the back squat at 85% of 1-repetition maximum across 4 conditions: (1) total load from free weight and (2) 20%, (3) 30%, and (4) 40% of the total load from elastic band and the remaining load from free weight. The eccentric and concentric phases of the back squat were divided into upper, middle, and bottom phases. Results: In the eccentric phase, mean velocity progressively increased with increasing elastic resistance, and muscle activity of the vastus medialis and rectus femoris significantly increased with the largest elastic resistance in the upper phase (P ≤.036). In the concentric phase, mean power (P ≤.021) and rate of force development (P ≤.002) significantly increased with increasing elastic resistance. Furthermore, muscle activity of the vastus lateralis and vastus medialis significantly improved with the largest elastic resistance in the upper phases (P ≤.021). Conclusion: Velocity, power, rate of force development, and selective muscle activity increased as the elastic resistance increased in different phases during the back-squat exercise. [ABSTRACT FROM AUTHOR]

Purpose: To compare the kinematic profile of 2 underwater pullout breaststroke techniques. Methods: Sixteen swimmers (9 men, 20.67 [2.71] y old; 7 women, 18.86 [0.83] y old) performed 3 × 25-m breaststroke using 2 pullout breaststroke techniques: Fly-Kick first and Combined. A speedometer was used to assess the peak and the mean velocity during the glide, propulsion, and recovery phases of both techniques, as well as for the total underwater sequence. The underwater distance was retrieved from video footage and was considered for each pullout technique. The range of motion of the knee during the fly-kick was also retrieved, and the time to complete the 25 m was considered the performance outcome, accompanied by the mean velocity, stroke rate, stroke length, and stroke index. Results: Velocity–time series showed different profiles between pullout techniques (P ≤.05) mostly in the glide and propulsion phases for males and females, respectively. The mean velocity of 25 m was shown to be greater in females when using the Fly-Kick first technique (P =.05, d = 0.36). Greater values in total underwater distance and knee range of motion were also observed for this technique in both cohorts. Conclusions: Female swimmers presented a higher performance when using the Fly-Kick first technique. Different kinematic profiles arise when swimmers use different underwater pullout techniques where the Fly-Kick first may allow them to reach higher kinematical standard. [ABSTRACT FROM AUTHOR]

Musculoskeletal modeling, typically implemented using marker-based systems in laboratory environments, is commonly used for noninvasive estimations of loads. Inertial measurement units (IMUs) have become an alternative for the evaluation of kinematics. However, estimates of spine joint contact forces using IMUs have yet to be thoroughly evaluated. Dynamics tasks and static postures from activities of daily living were captured on 11 healthy subjects using both systems simultaneously. Spine kinematics obtained from IMU- and marker-based systems and L4–L5 joint contact forces were compared. Lateral bending resulted in a weak agreement with significant differences between the 2 systems (P =.02, average root mean-squared error = 4.81), whereas flexion–extension and axial rotation exhibited the highest agreement with no significant differences (P <.05, average root mean-squared error = 5.51 and P <.31, average root mean-squared error = 5.08, respectively). All tasks showed excellent correlations (R2 =.76–.99) in estimated loads between systems. Differences in predicted loads at the L4–L5 were only observed during flexion–extension (1041 N vs 947 N, P =.0004) and walking with weights (814 N vs 727 N, P =.004). Different joint reaction force outcomes were obtained in 2 of the 8 tasks between systems, suggesting that IMUs can be robust tools allowing for convenient and less expensive evaluations and for longitudinal assessments inside and outside the laboratory setting. [ABSTRACT FROM AUTHOR]

This study investigated how data series length and gaps in human kinematic data impact the accuracy of Lyapunov exponents (LyE) calculations with and without cubic spline interpolation. Kinematic time series were manipulated to create various data series lengths (28% and 100% of original) and gap durations (0.05–0.20 s). Longer gaps generally resulted in significantly higher LyE% error values in each plane in noninterpolated data. During cubic spline interpolation, only the 0.20-second gap in frontal plane data resulted in a significantly higher LyE% error. Data series length did not significantly affect LyE% error in noninterpolated data. During cubic spline interpolation, sagittal plane LyE% errors were significantly higher at shorter versus longer data series lengths. These findings suggest that not interpolating gaps in data could lead to erroneously high LyE values and mischaracterization of movement variability. When applying cubic spline, a long gap length (0.20 s) in the frontal plane or a short sagittal plane data series length (1000 data points) could also lead to erroneously high LyE values and mischaracterization of movement variability. These insights emphasize the necessity of detailed reporting on gap durations, data series lengths, and interpolation techniques when characterizing human movement variability using LyE values. [ABSTRACT FROM AUTHOR]

Purpose: The optimal approach to hamstring training is heavily debated. Eccentric exercises reduce injury risk; however, it is argued that these exercises transfer poorly to improved hamstring function during sprinting. Some argue that other exercises, such as isometric exercises, result in better transfer to running gait and should be used when training to improve performance and reduce injury risk. Given the performance requirements of the hamstrings during the terminal swing phase, where they are exposed to high strain, exercises should aim to improve the torque production during this phase. This should improve the hamstrings' ability to resist overlengthening consequently, improving performance and limiting strain injury. Most hamstring training studies fail to assess running kinematics postintervention. Of the limited evidence available, only eccentric exercises demonstrate changes in swing-phase kinematics following training. Studies of other exercise modalities investigate effects on markers of performance and injury risk but do not investigate changes in running kinematics. Conclusions: Despite being inconsistent with principles of transfer, current evidence suggests that eccentric exercises result in transfer to swing-phase kinematics. Other exercise modalities may be effective, but the effect of these exercises on running kinematics is unknown. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of attentional focus instructions on the biomechanical variables associated with the risk of anterior cruciate ligament injury of the knee joint during a drop landing task using a time series analysis. Ten female volleyball players (age: 20.4 ± 0.8 years, height: 169.7 ± 7.1 cm, mass: 57.6 ± 3.1 kg, experience: 6.3 ± 0.8 years) performed landings from a 50 cm height under three different attentional focus conditions: (1) external focus (focus on landing as soft as possible), (2) internal focus (focus on bending your knees when you land), and (3) control (no-focus instruction). Statistical parameter mapping in the sagittal plane during the crucial first 30% of landing time showed a significant effect of attentional focus instructions. Despite the similarity in landing performance across foci instructions, adopting an external focus instruction promoted reduced vertical ground reaction force and lower sagittal flexion moment during the first 30% of execution time compared to internal focus, suggesting reduced knee loading. Therefore, adopting an external focus of attention was suggested to reduce most biomechanical risk variables in the sagittal plane associated with anterior cruciate ligament injuries, compared to internal focus and control condition. No significant differences were found in the frontal and horizontal planes between the conditions during this crucial interval. [ABSTRACT FROM AUTHOR]

Bilateral gait symmetry is an essential requirement for normal walking since asymmetric gait patterns increase the risk of falls and injuries. While human gait control heavily relies on the contribution of sensory inputs, the role of sensory systems in producing symmetric gait has remained unclear. This study evaluated the influence of vision as a dominant sensory system on symmetric gait production. Ten healthy adults performed treadmill walking with and without vision. Twenty-two gait parameters including ground reaction forces, joint range of motion, and other spatial–temporal gait variables were evaluated to quantify gait symmetry and compared between both visual conditions. Visual block caused increased asymmetry in most parameters of ground reaction force, however mainly in the vertical direction. When vision was blocked, symmetry of the ankle and knee joint range of motion decreased, but this change did not occur in the hip joint. Stance and swing time symmetry decreased during no-vision walking while no significant difference was found for step length symmetry between the two conditions. This study provides a comprehensive analysis to reveal how the visual system influences bilateral gait symmetry and highlights the important role of vision in gait control. This approach could be applied to investigate how vision alters gait symmetry in patients with disorders to help better understand the role of vision in pathological gaits. [ABSTRACT FROM AUTHOR]

Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction. [ABSTRACT FROM AUTHOR]

This study estimated the contribution of the midfoot joint complex (MJC) kinematics to the pelvis anterior–posterior positions during the stance phase of walking and investigated whether the MJC is functionally coordinated with the lower limb joints to maintain similar pelvic positions across steps. Hip, knee, ankle, and MJC sagittal angles were measured in 11 nondisabled participants during walking. The joints' contributions to pelvic positions were computed through equations derived from a link-segment model. Functional coordination across steps was identified when the MJC contribution to pelvic position varied and the summed contributions of other joints varied in the opposite direction (strong negative covariations [r ≤ −.7] in stance phase instants). We observed that the MJC plantarflexion (arch raising) during the midstance and late stance leads the pelvis backward, avoiding excessive forward displacement. The MJC was the second joint that contributed most to the pelvis positions (around 18% of all joints' contributions), after the ankle joint. The MJC and ankle were the joints that were most frequently coordinated with the other joints (≅70% of the stance phase duration). The findings suggest that the MJC is part of the kinematic chain that determines pelvis positions during walking and is functionally coordinated with the lower limb joints. [ABSTRACT FROM AUTHOR]

Individuals with knee osteoarthritis (KOA) and flat feet are more likely to experience increased pain and cartilage damage. This study aimed to investigate the knee kinetics, kinematics, pain, and physical function in individuals with moderate symptomatic KOA, in comparison to asymptomatic control participants. Thirty volunteers with moderate KOA (with flat feet n = 15, with normal feet n = 15) and 30 asymptomatic people (with flat feet n = 15, with normal feet n = 15) were evaluated. The knee adduction angular impulse, knee flexion moment, knee flexion angular impulse, and knee flexion angle were measured during level walking. The pain was assessed in patients with KOA. The study found that individuals with KOA had a significant increase in the knee adduction angular impulse compared with the asymptomatic people (P <.05). The KOA with flat feet group had significantly lower knee flexion moment, knee flexion angular impulse, and knee flexion angle values than the KOA with normal feet group (P <.05). Furthermore, the KOA with flat feet group had a higher pain score than the KOA with normal feet group. Individuals with osteoarthritis and flat feet had lower knee flexion moments which may indicate reduced knee force exerted through compensatory mechanisms. Despite this reduction, they reported significantly higher levels of pain compared with those without flat feet, a finding that warrants further investigation in future studies. [ABSTRACT FROM AUTHOR]

Purpose: To explore the association of the load–velocity (L-V) relationship variables and ability to maintain maximal mechanical performance during the prone bench-pull exercise with sprint swimming performance and in-water forces. Methods: Eleven competitive adult male swimmers (50-m front crawl World Aquatics points: 488 [66], performance level 4) performed 1 experimental session. The L-V relationship variables (L0 [ie, maximal theoretical load at 0 velocity]; v0 [ie, maximal theoretical velocity at 0 load], and Aline [ie, area under the L-V relationship]) and maximal mechanical maintenance capacity were assessed at the beginning of the session. Afterward, sprint swimming performance and in-water force production were tested through a 50-m front-crawl all-out trial and 15-s fully-tethered swimming, respectively. Results: Only v0 presented high positive associations with 50-m time and swimming kinematics (r >.532; P <.046). The L0, v0, and Aline showed very high positive associations with the in-water forces during tethered swimming (r >.523; P <.049). However, the ability to maintain maximal mechanical performance, assessed by the mean velocity decline during the prone bench pull, was only significantly correlated with stroke rate (r = −.647; P =.016) and stroke index (r =.614; P =.022). Conclusions: These findings indicate that maximal neuromuscular capacities, especially v0, have a stronger correlation with swimming performance and in-water force production than the ability to maintain maximal mechanical performance in level 4 swimmers. [ABSTRACT FROM AUTHOR]

Postpartum mothers are susceptible to lumbopelvic pain which may be exacerbated by loading, like carrying their infant in arms and with baby carriers. Nulliparous women carrying infant mannequins may biomechanically mimic mother–infant dyad, but this has not been studied. The purpose of our study was to investigate biomechanical differences of 10 mothers carrying their infants and 10 nulliparous women carrying infant mannequins under 3 gait conditions: carrying nothing, carrying in arms, and carrying in a baby carrier (babywearing). Spatiotemporal gait parameters, peak ground reaction forces and impulses, and lower extremity and trunk kinematics were collected using motion capture and force plates and compared using a mixed 2 × 3 (parity × condition) analysis of variance (α ≤.05). The largest differences occurred between carrying conditions: carrying in arms or babywearing increased vertical and anteroposterior ground reaction forces, trunk extension, ankle dorsiflexion, and hip and knee flexion. Kinematic differences were identified between arms and babywearing conditions. Together this suggests alterations in joint loading for both groups. Our study also contributes a novel understanding of postpartum health by demonstrating alterations in step time, anterior forces, and ankle and knee mechanics, suggesting that during gait, mothers carrying their own infants choose different propulsive strategies than nulliparous women carrying mannequins. [ABSTRACT FROM AUTHOR]

As markerless motion capture is increasingly used to measure 3-dimensional human pose, it is important to understand how markerless results can be interpreted alongside historical marker-based data and how they are impacted by clothing. We compared concurrent running kinematics and kinetics between marker-based and markerless motion capture, and between 2 markerless clothing conditions. Thirty adults ran on an instrumented treadmill wearing motion capture clothing while concurrent marker-based and markerless data were recorded, and ran a second time wearing athletic clothing (shorts and t-shirt) while markerless data were recorded. Differences calculated between the concurrent signals from both systems, and also between each participant's mean signals from both asynchronous clothing conditions were summarized across all participants using root mean square differences. Most kinematic and kinetic signals were visually consistent between systems and markerless clothing conditions. Between systems, joint center positions differed by 3 cm or less, sagittal plane joint angles differed by 5° or less, and frontal and transverse plane angles differed by 5° to 10°. Joint moments differed by 0.3 N·m/kg or less between systems. Differences were sensitive to segment coordinate system definitions, highlighting the effects of these definitions when comparing against historical data or other motion capture modalities. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the preliminary effects of movement pattern training (MoveTrain) versus strengthening/flexibility (standard) treatment on hip and pelvic biomechanics in patients with chronic hip-related groin pain. This is a secondary analysis of data collected during a pilot randomized clinical trial. Thirty patients with hip pain, between the ages of 15 and 40 years, were randomized to MoveTrain or standard. Both groups completed 10 treatment sessions over 12 weeks along with a daily home exercise program. Three-dimensional motion analysis was used to collect kinematic and kinetic data of the pelvis and hip during a single-leg squat task at pretreatment and immediately posttreatment. Compared with the standard group, the MoveTrain group demonstrated smaller hip adduction angles (P =.006) and smaller hip external adduction moments (P =.008) at posttreatment. The desired changes to hip joint biomechanics, as found in this study, may require specificity in training that could allow health care professionals to better customize the rehabilitation of patients with hip pain. These findings can also be applied to the design and implementation of future clinical trials to strengthen our understanding of the long-term implications of different rehabilitation techniques for patients with hip pain. [ABSTRACT FROM AUTHOR]

As markerless motion capture systems become more affordable than ever, it is becoming far easier to collect and analyze kinematic data on baseballers. To ensure this data can be used impactfully, coaches and practitioners should possess a good understanding of specific technique characteristics that are associated with enhanced performance in pitchers and hitters. This study used the open-source data provided by Driveline Baseball's OpenBiomechanics Project to evaluate the contribution of lower-body kinematics to pitch velocity and bat speed. In addition to correlational analyses to examine the association between discrete kinematic variables and performance, statistical nonparametric mapping was used to compare slow and fast velocity groups across the entirety of pitching and hitting motions from peak knee height to ball release/contact. It was found that rotation of the trail leg and extension of the lead knee were both associated with performance in pitchers and hitters. Consequently, coaches and practitioners should ensure that individuals possess an adequate level of strength and flexibility to facilitate optimal movement of the trail hip and lead knee during pitching and hitting movements. If deficiencies exist, then training programs should be designed to address these issues and eventually bring about an improvement in performance. [ABSTRACT FROM AUTHOR]

More than 80% of adult manual wheelchair users with spinal cord injuries will experience shoulder pain. Females and those with decreased shoulder dynamics variability are more likely to experience pain in adulthood. Sex-related differences in shoulder dynamics variability during pediatric manual wheelchair propulsion may influence the lifetime risk of pain. We evaluated the influence of sex on 3-dimensional shoulder complex joint dynamics variability in 25 (12 females and 13 males) pediatric manual wheelchair users with spinal cord injury. Within-subject variability was quantified using the coefficient of variation. Permutation tests evaluated sex-related differences in variability using an adjusted critical alpha of P =.001. No sex-related differences in sternoclavicular or acromioclavicular joint kinematics or glenohumeral joint dynamics variability were observed (all P ≥.042). Variability in motion, forces, and moments are considered important components of healthy joint function, as reduced variability may increase the likelihood of repetitive strain injury and pain. While further work is needed to generalize our results to other manual wheelchair user populations across the life span, our findings suggest that sex does not influence joint dynamics variability in pediatric manual wheelchair users with spinal cord injury. [ABSTRACT FROM AUTHOR]

Purpose: Power output is dependent on the load used during exercise such as bench-press throw (BPT). Attentional focus (external [EXT] vs internal [INT]) during exercise significantly modulates power performance. The purpose of the present study was to examine the effects of load and attentional focus on mechanical parameters during BPT. Methods: In a crossover study, 31 resistance-trained men (mean age 23.5 [3.0] y) performed BPT at 30% (light), 50% (moderate), and 70% (heavy) of 1-repetition maximum (1-RM) using an INT or EXT focus of attention in randomized order. A linear encoder was used to identify barbell vertical displacement, throw time, peak/average velocity, force, and power during the concentric lifting phase. Results: Statistical analysis revealed significant load × focus interaction effects for velocity and vertical displacement (P ≤.045; 0.66 ≤ d ≤ 0.89). Post hoc analyses indicated significantly larger velocities and displacements at 30% and 70% of 1-RM in favor of EXT (P ≤.038; 0.79 ≤ d ≤ 1.13) but similar values at 50% of 1-RM (P >.05). Furthermore, significant main effects of load were found for throw time, force, and power (P <.001; 4.20 ≤ d ≤ 14.0). While time and force gradually increased with higher loads (P <.001; 1.45 ≤ d ≤ 14.0), power output was larger at 50% compared with 30% and 70% 1-RM (P <.001; 3.09 ≤ d ≤ 7.07), irrespective of attentional focus. Conclusions: The present findings indicated that practitioners may use EXT over INT attentional focus to enhance velocity and vertical displacement during BPT at light and heavy loads (ie, 30% and 70% 1-RM). At moderate loads (ie, 50% 1-RM), mechanical bench-press parameters appear to be less affected by attentional focus. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r >.770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance. [ABSTRACT FROM AUTHOR]

This study aimed to determine the acute effects of static stretching of the hamstrings on maximal sprint speed and its spatiotemporal variables and lower-limb kinematics during the late swing phase, as well as the relationship with Nordic hamstring strength. The study had a within-participant experimental design. Sixteen healthy male college sprinters were asked to sprint 80 m without static stretching and with static stretching of the hamstrings for 4 x 30 s per leg before the sprint: both conditions were counterbalanced. The knee ftexion peak torque was measured using the Nordic hamstring. The differences between no static stretching and static stretching as well as their relationship with Nordic hamstri ng strength were investigated. The results showed that the touchdown distance (p = .036) significantly increased following static stretching. Although not significant. maximal sprint speed decreased (p = .086), and the theoretical hamstring length (difference between knee angle and hip angle) at ipsilateral touchdown was greater (p =.069) following static stretching. In addition, a lower peak torque of the Nordic hamstring resulted in a more significant decrease in maximal sprint speed following static stretching. Therefore, static stretching of the hamstring just before sprinting may increase the theoretical hamstring length during the late swing phase at maximal sprint speed and induce kinematics that increases the hamstring strain injury risk. Moreover, it is suggested that improving the Nordic hamstring strength may help minimize the negative effects of static stretching on the hamstrings. [ABSTRACT FROM AUTHOR]

Context: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). Design: A correlation study. Methods: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. Results: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between −.3 and.1). Conclusions: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump. [ABSTRACT FROM AUTHOR]

Prior studies have explored the relationship between knee valgus and musculoskeletal variables to formulate injury prevention programs, primarily for females. Nonetheless, there is insufficient evidence pertaining to professional male soccer players. Here, the aim was to test the correlation of lateral trunk inclination, hip adduction, hip internal rotation, ankle dorsiflexion range of motion, and hip isometric strength with knee valgus during the single-leg vertical jump test. Twenty-four professional male soccer players performed a single-leg vertical hop test, hip strength assessments, and an ankle dorsiflexion range of motion test. A motion analysis system was employed for kinematic analysis. Maximal isometric hip strength and ankle dorsiflexion range of motion were tested using a handheld dynamometer and a digital inclinometer, respectively. The correlation of peak knee valgus with peak lateral trunk inclination was.43 during the landing phase (P =.04) and with peak hip internal rotation was −.68 (P <.001). For knee valgus angular displacement, only peak lateral trunk inclination presented a moderate positive correlation (r =.40, P =.05). This study showed that trunk and hip kinematics are associated with knee valgus, which could consequently lead to increased knee overload in male professional soccer players following a unilateral vertical landing test. [ABSTRACT FROM AUTHOR]

There is mixed evidence on the role that biological sex plays in shoulder biomechanics despite known differences in musculoskeletal disorder prevalence between males and females. Additionally, advancing age may contribute to shoulder kinematic changes. The purpose of this study was to determine if sex and age influenced scapular and thoracohumeral kinematics during a range of functional tasks. Sixty healthy participants aged 19–63 years (30 males; 30 females) completed a functional task protocol while their upper limb motion was recorded. Scapular and humeral angles were calculated and compared with multiple linear regressions to assess the interaction effects of sex and age. Shoulder kinematics were not different between sex and age groups for many of the functional tasks. However, females had lower humeral external rotation in the overhead lift task (15°, P <.001), and less scapular anterior tilt angles in the forward transfer task (6°, P <.001) than males. Age was positively associated with humeral elevation (R2 =.330, P <.001) and scapular rotation (R2 =.299, P <.001) in the Wash Axilla task. There exist some kinematic differences between sex and with advancing age for select functional tasks, which should be considered for musculoskeletal disorder development. [ABSTRACT FROM AUTHOR]

The present randomized study investigated the effect of acute supplementation of 800 mg/kg of ketone monoester ingestion (KE) or placebo (PL) and 210 mg/kg of NaHCO3 co-ingestion on cycling performance of WorldTour cyclists during a road cycling stage simulation. Twenty-eight cyclists participated in the study (27.46 ± 4.32 years; 1.80 ± 0.06 m; 69.74 ± 6.36 kg). Performance, physiological, biochemical, and metabolism outcomes, gut discomfort, and effort perceived were assessed during a road cycling simulation composed of an 8-min time-trial (TT) performance + 30-s TT + 4.5 hr of outdoor cycling + a second 8-min TT + a second 30-s TT. Greater absolute and relative mean power during the first 8-min TT (F = 5.067, p =.033, η p 2 =.163 , F = 5.339, p =.029, η p 2 =.170 , respectively) was observed after KE than after PL (KE: 389 ± 34, PL: 378 ± 44 W, p =.002, d = 0.294 and KE: 5.60 ± 0.42, PL: 5.41 ± 0.44 W/kg, p =.001, d = 0.442). Additionally, greater concentration of β-hydroxybutyrate blood concentration (F = 42.195, p <.001, η p 2 =.619) was observed after KE than after PL during the first steps of the stage (e.g., after warm-up KE: 1.223 ± 0.642, PL: 0.044 ± 0.058 mM, p <.001, d = 2.589), although the concentrations returned to near baseline after 4.5 hr of outdoor cycling. Moreover, higher values of anion gap were observed (F = 2.333, p =.026, η p 2 =.080) after KE than after PL ingestion, after the warm-up and after the first 8-min and 30-s TT. Additionally, lower concentrations of HCO 3 − were reported in the KE condition after warm-up and after the first 8-min and 30-s TT. During the initial phase of the stage simulation, acute supplementation with KE + NaHCO3 co-ingestion enhanced 8-min TT cycling performance (3.1%) in WorldTour cyclists with a concomitant hyperketonaemia. [ABSTRACT FROM AUTHOR]

At present, ginkgo leaves are still picked manually. A brush roller ginkgo leaf picker has been designed to improve harvesting efficiency and reduce losses caused by manual failure to pick leaves in time under large-scale planting areas. The ginkgo leaf picker is mainly composed of crawler chassis, gantry frame, brush roller picking parts, and collecting box. The kinematics of the brush roller are analyzed for the picking omission situation. An experimental platform for picking ginkgo biloba leaves was established. Three parameters, namely roller speed, moving speed, and roller inclination were selected for optimization. Then the maximum net harvest rate and the minimum damage rate were achieved. The orthogonal test showed that when the roller speed was 130 rev/min, the moving speed was 0.25 m/s, and the roller inclination was 32°, the picking effect was the best, the net harvest rate was 93.32%, the damage rate was 1.42%, and the damage degree of the trunks was slight. The experiment proved that the brush-roller ginkgo leaf picker has a good picking effect, which can provide a reference for the optimization design of ginkgo leaf harvesting machinery under the dwarf dense planting mode. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study is to evaluate how gait kinematics and muscle activity during robot-assisted gait training are affected by different combinations of parameter settings and a number of instruction types, ranging from no instructions to goal-specific instructions. Design: Robots for gait therapy provide a haptic guidance, but too much guidance can limit the active participation. Therapists can stimulate this active participation either with instructions or by adapting device parameters. How these two factors interact is still unknown. In the present study, we test the interaction of three different parameter settings and four instruction types in a cross-sectional study with 20 children and adolescents without impairment. Gait kinematics and surface electromyography were measured to evaluate the immediate effects. Results: We found that only goal-specific instructions in combination with a low guidance led to a moderate but significant change in gait kinematics. The muscle activity was altered by all instructions, but the biggest effect was found for goal-specific instructions with a 2.5 times higher surface electromyography amplitude compared to no instruction. Conclusions: Goal-specific instructions are a key element of robot assisted gait therapy interventions and device parameter adjustments may be used to modulate their effects. Therapists should pay close attention to how they instruct patients. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the effect of neuromuscular electrical stimulation on the frontal ankle motor control in individuals with chronic ankle instability during drop landing. Design: This was a randomized, controlled, double-blind trial. Thirtysix individuals with chronic ankle instability were randomly assigned to each group. Participants received 6-wk neuromuscular electrical stimulation intervention and sham stimulation in the neuromuscular electrical stimulation and control groups, respectively. Data were collected at week0 and week6. A mixed-effects model and analysis of covariance were employed to investigate the between-group differences in continuous and discrete outcome variables at week6, with the outcome variables at week0 as covariates. Results: Compared to control group, neuromuscular electrical stimulation group exhibited a 2.66° (2.45, 2.86) reduction in frontal ankle inversion angle, a 47.41°/sec (−16.05, −78.77) decrease in peak ankle inversion angular velocity, and a 0.43 Nm/kg (0.18, 0.68) increase in peak ankle eversion moment during drop landing at week6. Conclusions: Applying 6-wk neuromuscular electrical stimulation to the fibularis longus resulted in decreased ankle inversion angle and ankle inversion angular velocity and increased peak ankle eversion moment during drop landing. Consequently, neuromuscular electrical stimulation could be considered an effective modality for individuals with chronic ankle instability to enhance the frontal ankle movement patterns and overall ankle motor control. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to assess the impact of combining transcranial direct current stimulation with end-effector robot-assisted treatment on upper limb function, spasticity, and hand dexterity in chronic stroke patients. Design: This was a prospective, double-blind randomized trial with 20 equally allocated stroke patients. The experimental group received dual transcranial direct current stimulation (anode over affected M1, cathode over contralateral M1) alongside robot-assisted treatment, while the control group received sham transcranial direct current stimulation with the same electrode placement + robot-assisted treatment. Each patient underwent 20 combined transcranial direct current stimulation and robot-assisted treatment sessions. The primary outcome measure was the Fugl-Meyer Upper Limb motor score, with secondary outcomes including AMADEO kinematic measures, Action Research Arm Test, and Functional Independence Measure. Assessments were conducted at baseline, after rehabilitation, and 3 mos later. Results: Combining bilateral transcranial direct current stimulation with robot-assisted treatment did not yield additional improvements in Fugl Meyer Upper Limb motor score, Functional Independence Measure, or Action Research Arm Test scores among stroke patients. However, the real transcranial direct current stimulation group showed enhanced finger flexion in the affected hand based on AMADEO kinematic measures. Conclusions: The addition of transcranial direct current stimulation to robot-assisted treatment did not result in significant overall functional improvements in chronic stroke patients. However, a benefit was observed in finger flexion of the affected hand. [ABSTRACT FROM AUTHOR]

Grinding stones are a worldwide technology, instrumental in processing food as far back as the African Middle Stone Age. Research interest in grinding stones, and the usewear on their surfaces, has grown in the last few decades. Models of grinding stone manufacture, use, and discard provide a reference for cross-cultural comparisons of practices and guide methodologies in planning usewear analysis based on kinetics. In Ethiopia, traditional knowledge of grinding stones is still accessible, and grinding stones remain in use. The models developed through interviews with, and observations of, local practitioners show processes and behaviors but also decisions made at various stages. Particular behaviors and decisions have impacts on tool wear. [ABSTRACT FROM AUTHOR]

Total knee arthroplasty (TKA) is an end-stage treatment for knee osteoarthritis that relieves pain and loss of mobility, but patient satisfaction and revision rates require improvement. One cause for TKA revision is joint instability, which may be due to improper ligament balancing. A better understanding of the relationship between prosthesis design, alignment, and ligament engagement is necessary to improve component designs and surgical techniques to achieve better outcomes. We investigated the biomechanical effects of ligament model complexity and ligament wrapping during laxity tests using a virtual joint motion simulator. There was little difference in kinematics due to ligament complexity or ligament wrapping. [ABSTRACT FROM AUTHOR]

Early warning systems (EWSs) for landslides are becoming a pivotal tool to safeguard assets and stakeholders. With this mission, an EWS should be capable of reliably forecasting the failure time when the ground accelerates. There are analytical methods developed to this end that use time-series kinematics: inverse velocity (INV), minimum inverse velocity (MINV), slope gradient (SLO), and velocity over acceleration (VOA). Although an abundant number of studies applied these methods, they have been majorly examined in a back-analysis context where all the measurements are incorporated into the forecasting process. A successful operation of EWSs in raising meaningful alarms calls for an examination in which the forecasting method is evaluated synchronously. This study evaluates the ability of the four mentioned methods to provide reliable forecasts in real time using a comprehensive database including 75 historical failures. For the first time, the methods are evaluated using a quantitative metric called reliability fitness index (RFI) that measures the portion of forecasts meeting an accuracy threshold. For accuracy thresholds of 50, 75 and 90%, INV showed the highest RFI values of 16, 7, and 4% followed by SLO values of 12, 5, and 2%, respectively. Opposing reliability values for SLO and INV suggest EWSs should take advantage of hybrid models that consider both methods. [ABSTRACT FROM AUTHOR]

Many recent studies have used boil-and-bite style instrumented mouthguards to measure head kinematics during impact in sports. Instrumented mouthguards promise greater accuracy than their predecessors because of their superior ability to couple directly to the skull. These mouthguards have been validated in the lab and on the field, but little is known about the effects of decoupling during impact. Decoupling can occur for various reasons, such as poor initial fit, wear-and-tear, or excessive impact forces. To understand how decoupling influences measured kinematic error, we fit a boil-and-bite instrumented mouthguard to a 3D-printed dentition mounted to a National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform. We also instrumented the headform with linear accelerometers and angular rate sensors at its center of gravity (CG). We performed a series of pendulum impact tests, varying impactor face and impact direction. We measured linear acceleration and angular velocity, and we calculated angular acceleration from the mouthguard and the headform CG. We created decoupling conditions by varying the gap between the lower jaw and the bottom face of the mouthguard. We tested three gap conditions: 0 mm (control), 1.6 mm, and 4.8 mm. Mouthguard measurements were transformed to the CG and compared to the reference measurements. We found that gap condition, impact duration, and impact direction significantly influenced mouthguard measurement error. Error was higher for larger gaps and in frontal (front and front boss) conditions. Higher errors were also found in padded conditions, but the mouthguards did not collect all rigid impacts due to inherent limitations. We present characteristic decoupling time history curves for each kinematic measurement. Exemplary frequency spectra indicating characteristic decoupling frequencies are also described. Researchers using boil-and-bite instrumented mouthguards should be aware of their limitations when interpreting results and should seek to address decoupling through advanced post-processing techniques when possible. [ABSTRACT FROM AUTHOR]

Robot technology is considered one of the most promising technologies to achieve intelligent production, with picking robots being the most common type. Picking robots are highly integrated mechatronic systems, which autonomously complete tasks including picking, carrying, and sorting. The application of picking robots enhances the efficiency of production across various environments. In this paper, a classification-design-optimization-application integrated framework of picking robots is addressed, contributing to theoretical research and application of picking robots. Classification of picking robot is established and analyzed considering the differences of overall form and end-effector to guide the development of research strategies and approaches of picking robot. Design of picking robot is described from different aspects of the target, structure, monitoring, and control design. Additionally, the commonly used optimization methods for picking robots, including structural parameters, kinematics and dynamics, and energy consumption, are discussed. Finally, the application of picking robots under different environments is expounded, and the challenges and prospects of picking robots are highlighted. This study could present theoretical support and application measures for picking robot study and technology development. [ABSTRACT FROM AUTHOR]

Generalizing smooth volumetric growth to the singular case, using de Rham currents and flat chains, we demonstrate how regular boundaries of bodies may evolve to fractals. [ABSTRACT FROM AUTHOR]

A second-order multiscale theory based on the concept of a Representative Volume Element (RVE) is proposed to link a classical poromechanical model at the RVE scale to a high-order poromechanical model at the macro-scale in the context of finite-strain kinematics. The proposed theory is carefully derived from the Principle of Multiscale Virtual Power, which is a generalization of the Hill-Mandel Principle of Macrohomogeneity. The coupled governing equations of the low-scale and the homogenization rules for the flux and stress-like quantities are obtained by means of standard variational arguments. The main theoretical result is that the minimally constrained space for the pore pressure field allows for non-zero net fluid flow across the RVE boundaries, unlike first-order theories. The direct consequence of this finding is that the present theory can be consistently applied in cases where the low-scale (RVE level) exhibits substantial volume changes (swelling or shrinking) as a consequence of the evolution of the macro-scale kinematics. Details of formulation development and expression for the homogenized tangent operators are presented for those interested in the computational implementation of the model. [ABSTRACT FROM AUTHOR]

The teleoperation of robotic manipulators allows extending the capabilities of human operators to work in different scales and distances to improve the efficiency of tasks that require high precision and repeatability. However, the lack of kinesthetics makes teleoperation difficult under diminished visibility or during palpation tasks despite visual and auditory feedback. This work presents the design and implementation of a haptic teleoperation system based on a master–slave hybrid control scheme. The robotic system uses a haptic device and a joystick to map the desired pose of the robot, while a force sensor located in the end-effector provides stiffness perception. The implemented control algorithm employs a weighted quadratic program to compute the inverse kinematics at different scales, allowing the system to operate over delicate and uneven surfaces, such as those found in surgical incisions. Finally, experimental results are shown, where the performance of the haptic system in cutting porcine tissue and manipulation tasks inside the free workspace are discussed. [ABSTRACT FROM AUTHOR]

The analysis of gait is an important tool for evaluating postoperative outcomes of a Total Knee Replacement (TKR). There are few studies which have evaluated the gait parameters of a Kinematic retaining (Kr) prosthesis. This study therefore aims to investigate the kinetic and kinematic differences of running and walking, in the ankle, knee and hip joints in patients who underwent a Kr TKR. This study assessed the gait of 12 patients with physica lima Kr TKRs at 1 year follow up and 8 healthy controls using 3D video analysis. Data was collected on the kinetics and kinematics of walking and running at the ankle, knee and hip. Comparison was made between the operated and non-operated limbs of the patients, and between the operated and control limbs. Gait analysis showed no statistically significant difference in the hip, ankle and knee angles or moments between the non-operated and operated legs during walking and running. However, there was a statistically significant difference between the knee angles of initial contact, maximum flexion during stance and swing in the TKR knees vs controls in walking and running. Similarly, there was also a statistically significantly higher max knee flexion moment between operated knees and controls in both walking and running. This study has shown that a quadriceps avoidance gait persists in patients after TKR, and that there was symmetry and reciprocated gait parameters in non-operated limbs. These findings suggest that Kr TKRs could be capable of replicating normal knee kinematics when running and walking. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of a five-week training program on undulatory underwater swimming (UUS) in swimmers and to compare the specific effects prompted by two different training protocols on UUS performance and kinematics. Swimmers (n = 14) were divided into in-water only (WO) (18.61 ± 2.62 years, FINA points: 507 ± 60) and water + dry-land training groups (with conical pulleys) (WD) (18.38 ± 2.67 years, FINA points: 508 ± 83). Three countermovement jumps (CMJ) and three maximal UUS trials were performed before and after a five-week training period. The training program comprised 14 × 30-min sessions. The WO group repeated the same 15-min block twice, while the WD group performed one block of 15 min in the water and the other block on land performing lower limb exercises with conical pulleys. Seven body landmarks were auto-digitalized during UUS by a pre-trained neural network and 21 kinematic variables were calculated. The level of statistical significance was set at p < 0.05. Significant time × group interaction in favour of the WD group was observed for mean vertical toe velocity (p = 0.035, η²p = 0.32). The WD group experienced enhancements in mean and maximum underwater velocity, kick frequency, maximum shoulder angular velocity, as well as mean and maximum vertical toe velocity (p < 0.05). The WO group exhibited an enhancement in CMJ height (p < 0.05). In conclusion, UUS performance was improved in adolescent swimmers after five weeks of specific training, only when combining water and conical pulley exercises. Coaches should include dry-land specific lower limb exercises in addition to in-water training to improve UUS performance. [ABSTRACT FROM AUTHOR]

Purpose: Most shoulder pathologies are associated with altered scapular kinematics which is mentioned as scapular dyskinesis. Scapular mobility, especially in upward rotation, measurement is essential for diagnosis and treatment. Easy-to-use, clinically applicable 2-dimensional (2-D) measurements would show excellent intra-tester reliability. To quantify intra-tester reliability for measuring scapular upward rotation in individuals with scapular dyskinesias, the landmark palpation with a video annotation tool was used. Methods: Ten participants with scapular dyskinesis were recruited. Scapular upward rotation was measured at rest, 30∘, 60∘, 90∘, and 120∘ of humeral elevation in the coronal plane both raising and lowering phases. Two trials were conducted for each arm position randomly, and an assessor took the pictures throughout. The video annotation tool (2-D Kinovia program) was used for measuring scapular upward rotation angles between days. The intra-tester reliability of scapular upward rotation was calculated. Results: This measurement technique demonstrated excellent intra-tester reliability (ICC3,1 = 0.98), range 0.96–0.99, and standard error of measurement was less than 1∘. Conclusions: The findings demonstrated that using this technique to measure scapular upward rotation was reliable in subjects with scapular dyskinesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Kinesio taping has been widely used as a means of sports protection, but its role as a means to correct abnormal biomechanical changes of the lower limbs during side-step cutting remains unclear. OBJECTIVE: To analyze and compare the changes in lower limb kinematics and dynamics when the subjects complete the side-step cutting of the knee joint under the conditions of kinesio taping, placebo taping and blank control. METHODS: Thirty-nine male college students majoring in basketball were recruited as subjects. Each subject was tested with kinesio taping, placebo taping or no taping. The mechanical correction method was used to patch the dominant knee joint of each subject. The run-up speed of 4.5-5.5 m/s was selected to complete the 45° side-step cutting motion, and the kinematics and kinetics data were collected synchronously by the three-dimensional dynamic capture system and the force measuring platform. The kinematics and kinetics parameters at the moment of initial touchdown and peak ground reaction force were selected for data analysis. SPSS 27.0 software was used for statistical analysis of the test data. RESULTS AND CONCLUSION: Kinematic indexes: compared with no taping and placebo taping, the hip abduction and knee valgus angles at the initial touchdown moment were significantly decreased when kinesio taping was used (P < 0.05); at the moment of peak lateral ground reaction force, the angles of hip abduction, knee valgus and ankle plantar flexion decreased significantly (P < 0.05), and the knee flexion angle was significantly increased (P < 0.05). Kinetic indexes: Compared with no taping, both kinesio taping and placebo taping significantly reduced hip abduction and external rotation torque, knee valgus and external rotation torque at the moment of initial touchdown (P < 0.05), and significantly reduced peak vertical ground reaction force and peak horizontal backward ground reaction force (P < 0.05); in addition, kinesio taping significantly reduced peak lateral ground reaction force compared with no taping and placebo taping (P < 0.05). These results indicate that kinesio taping of the knee joint may improve some kinematic and kinetic indexes associated with lower limb injury risk factors during the completion of the side-step cutting in basketball specialized college students to some extent, and may have a positive effect on the prevention of injury during the side-step cutting. In addition, the trends in the effects of placebo taping and kinesio taping on the knee joint are more consistent in terms of changes in some indexes, suggesting that there may be a placebo effect on the mechanism of action of kinesio taping. [ABSTRACT FROM AUTHOR]

Quantitative three-dimensional gait analysis has been used to evaluate the loading at the knee (i.e. external knee adduction moment, EKAM) during level ground walking in individuals with knee osteoarthritis (OA). The magnitude of EKAM can be influenced by some factors, such as knee marker position and foot placement angles in static calibration trials, which may lead to inaccurate functional assessments and intervention planning. This study aimed to clarify the effects of knee position during static calibration trials on the evaluation of knee loading during gait in individuals with medial knee OA. Seventeen individuals with medial knee OA completed three different static standing trials; (1) knee flexed at 0 degrees, (2) knee flexed at 15 degrees, and (3) knee flexed at 30 degrees before walking at their self-selected speed. A sixteen-camera three-dimensional VICON gait analysis system with four AMTI force platforms was used to collect the EKAM, knee adduction angular impulse (KAAI), knee joint center (KJC), and other knee kinematic and kinetic variables during gait. A repeated measures ANOVA was used to investigate the differences between conditions. The 1st peak of EKAM, the 1st peak EKAM arm, KAAI, and knee extension moment were significantly increased at the 15-degree and 30-degree conditions in comparison with the 0-degree condition (P < 0.05). Additionally, the knee flexion moment and knee external rotation moment were significantly reduced at the 15-degree and 30-degree conditions in comparison with the 0-degree condition (P < 0.05). All biomechanical variables were influenced by the localization of the KJC during static calibration trials. The changes in knee position during static trials significantly affected the 1st peak EKAM, KAAI, and other knee kinematics and kinetics variables during gait. Therefore, future studies should consider keeping the participants’ knees in a consistent position during static trials between visits, as the variations in knee position could mask or exaggerate the differences between groups and interventions. [ABSTRACT FROM AUTHOR]

Introduction: Stiffness (k) describes a material’s resistance to deformation and is useful for understanding neuromuscular function, performance, and injury risk. The aim of this study is to compare the lower limb stiffness method (kLLS), which uses only force plate data, with methods combining force plate and motion capture data to calculate stiffness during the eccentric phase of a countermovement. Material and Methods: Twelve resistance-trained males: age 24.9 (4.4) years, height 1.81 (0.05) m, weight 88.2 (14) kg) performed three maximal effort countermovement jumps (CMJ). Data were collected synchronously using three-dimensional (3D) kinematic and kinetic data (dual force plate setup). Lower limb stiffness (z), joint stiffness (x, y, and z), and leg stiffness (linear, sagittal plane, and 3D) were calculated for the eccentric phase of all CMs. Results: kLLS showed high concurrent validity with strong correlations to kinetic-kinematic methods (r = 0.90-0.97, p < 0.05). A linear mixed model revealed no significant differences in k-values between kLLS and leg stiffness, indicating high concurrent validity. Discussion: kLLS offers valid and valuable information affecting performance, injury risk, and return-to-sport decisions. Conclusion: The findings suggest that kLLS is a valid method for calculating stiffness in CMJs and equal to 3D leg stiffness. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the variation of individual and group competitive learning strategies on technique, kinematic variables in the front crawl stroke swimming, and intelligent physical-motor among swimming level 2 course students. The sample of the study consisted of 16 students, it was selected based on Intentional style of swimming level 2 course students involved in the second semester (2018/2019) who divided into two similar groups; A: control group (8) students learning with the traditional style, B: experimental group (8) students learning with competitive strategy. The following variables have been measured: skill level, frequency and stroke length, and speed of swimming 50m at front crawl stroke as well as intelligent physical-motor. The results of the study showed that the traditional learning method has a positive impact on improving skillfulness and speed of swimming 50 m at front crawl stroke performance. On the other hand, a competitive learning strategy has a significant effect in improving the performance of swimming 50m at front crawl stroke between students. The researcher recommends using a competitive learning strategy better when implementing swimming education programs to enhance technique skills and mechanical performance in front crawl stroke swimming and evaluate the level of intelligent physical-motor to know the right and viable strategy that would be used in swimming learning and use the results of kinetic analysis when evaluating students swimming to give feedback to detect weaknesses in performance to modify them. [ABSTRACT FROM AUTHOR]

The circumgalactic medium (CGM) hosts many physical processes with different kinematic signatures that affect galaxy evolution. We address the CGM–galaxy kinematic connection by quantifying the fraction of H  i that is aligned with galaxy rotation with the equivalent width co-rotation fraction, |$f_{\rm EWcorot}$|⁠. Using 70 quasar sightlines having Hubble Space Telescope /Cosmic Origins Spectrograph H  i absorption (⁠|${12\lt \log (N(\rm{{\rm H}\,{\small I}})/{\rm cm}^{-2})\lt 20}$|⁠) within |$5R_{\rm vir}$| of |$z\lt 0.6$| galaxies we find that |$f_{\rm EWcorot}$| increases with increasing H  i column density. |$f_{\rm EWcorot}$| is flat at |$\sim 0.6$| within |$R_{\rm vir}$| and decreases beyond |$R_{\rm vir}$| to |$f_{\rm EWcorot}$| |$\sim 0.35$|⁠. |$f_{\rm EWcorot}$| also has a flat distribution with azimuthal and inclination angles within |$R_{\rm vir}$|⁠ , but decreases by a factor of two outside of |$R_{\rm vir}$| for minor axis gas and by a factor of 2 for edge-on galaxies. Inside |$R_{\rm vir}$|⁠ , co-rotation dominated H i is located within |$\sim 20$| deg of the major and minor axes. We surprisingly find equal amounts of H  i absorption consistent with co-rotation along both major and minor axes within |$R_{\rm vir}$|⁠. However, this co-rotation disappears along the minor axis beyond |$R_{\rm vir}$|⁠ , suggesting that if this gas is from outflows, then it is bound to galaxies. |$f_{\rm EWcorot}$| is constant over two decades of halo mass, with no decrease for log(M |$_{\rm h}/{\rm M}_{\odot })\gt 12$| as expected from simulations. Our results suggest that co-rotating gas flows are best found by searching for higher column density gas within |$R_{\rm vir}$| and near the major and minor axes. [ABSTRACT FROM AUTHOR]

This study compared lower extremity, trunk, and upper extremity kinematics between tee and front toss hitting in youth baseball athletes. Twenty youth baseball athletes (14.3±2.9 yrs) performed three maximal effort swings off front toss and tee. Kinematic data were collected during the preparatory and acceleration phases. Lower extremity, trunk, and upper extremity kinematics were compared between tee and front toss hitting using 1-dimensional statistical parametric mapping (SPM). There was a significant difference in trunk kinematics between tee and front toss during the preparatory phase (p=.001); the trunk rotated more toward the back side when hitting off a tee compared to front toss (p<0.001). There was also a significant difference in trunk kinematics between tee and front toss for 67% of the acceleration phase; the trunk rotated more towards the back side from 0 to 67% when hitting off the tee (p<0.001). Significant differences were found in trunk kinematics between tee and front toss hitting in youth baseball players, where the trunk is less rotated toward the pitcher in the tee than in the front toss. Coaches utilize various training modalities to enhance hitting performance; however, differences in trunk kinematics should be considered between modalities when developing fundamental hitting techiques in youth baseball athletes. [ABSTRACT FROM AUTHOR]

Kinematic principle in lapping process is an essential theoretical foundation to achieve high lapping accuracy. The motion path of abrasive grains determines the machined area on workpiece, thereby affecting the surface accuracy. To improve lapping uniformity, this paper established a kinematic model of swing fixed-abrasive lapping (SFAL) and investigated the effect of kinematic parameters (rotational speed ratio, swing ratio, swing angle) on lapping uniformity. Non-uniformity coefficient (NUC) was adopted to evaluate the lapping uniformity, and the impact mechanism of kinematic parameters on the trajectory of abrasive grains were revealed by Taguchi experiments and numerical simulation. Furthermore, response surface experiments were employed to optimize the parameter combination, and a prediction model for NUC was developed. This work provides theoretical guidance for the selection of kinematic parameters in SFAL process, and has reference significance for improving the lapping accuracy. [ABSTRACT FROM AUTHOR]

AbstractMany researchers are interested in how the kinematics of reach-to-grasp movements in virtual reality (VR), which involve the vergence–accommodation conflict, differ from real space. The present study, conducted in VR, verified the effect of a discrepancy between visual and haptic target size and found that terminal haptic feedback is weighted more heavily than visual information, as is the case in real space. Furthermore, we investigated how the presence or absence of terminal haptic feedback modulates performance in VR by comparing prehension with or without terminal haptic feedback in VR, closed-loop natural grasping in real space, and pantomimed prehension with the eyes closed. Our results suggested that the contribution of a visual image to grip aperture adjustment is quite marginal in situations where terminal haptic feedback is unavailable, and that the performance in VR without haptic feedback is highly correlated with performances driven by fully internal representations (i.e., pantomimed movements). [ABSTRACT FROM AUTHOR]

The purpose of this quasiexperimental study was to test the effects of wearing the NewGait rehabilitative device on walking abilities in individuals with foot drop. The study involved 16 participants with foot drops caused by stroke (11 participants), multiple sclerosis (one participant), and peripheral neuropathies (four individuals). During a single testing session, participants walked 12 m at their self‐selected speed in four experimental conditions: walking without any orthotic device; walking while wearing a regular plastic posterior leaf ankle foot orthosis (AFO); walking with the NewGait device assisting ankle dorsiflexion only; and walking with the NewGait device assisting the hip, knee, and ankle joint motions. Body motions during walking were recorded using a 3D system for motion analysis and analyzed with a set of spatiotemporal and kinematic parameters and a gait decomposition index. The gait decomposition index indicated sagittal interjoint coordination in the three joint pairs (hip–knee, knee–ankle, and hip–ankle) of the paretic (foot drop) leg during walking and was validated in a previous study. Overall, wearing all three orthotic devices improved the gait velocity, ankle dorsiflexion, and foot clearance compared to gait trials in which no assistive devices were used. However, wearing the AFO significantly restricted the plantarflexion range of motion and decreased interjoint coordination as measured by joint decomposition. In contrast, the NewGait device altered the ankle plantarflexion motions but also increased coordinated movement (reduced the decomposition) in most lower‐extremity joint pairs and conditions. Therefore, the NewGait rehabilitative device can be considered superior to a regular AFO in correcting gait deviations caused by foot drop. [ABSTRACT FROM AUTHOR]

This paper introduces the flexible control and trajectory planning medical two-arm surgical robots, and employs effective collision detection methods to ensure the safety and precision during tasks. Firstly, the DH method is employed to establish relative rotation matrices between coordinate systems, determining the relative relationships of each joint link. A neural network based on a multilayer perceptron is proposed to solve FKP problem in real time. Secondly, a universal interpolator based on Non-Uniform Rational B-Splines (NURBS) is developed, capable of handling any geometric shape to ensure smooth and flexible motion trajectories. Finally, we developed a generalized momentum observer to detect external collisions, eliminating the need for external sensors and thereby reducing mechanical complexity and cost. The experiments verify the effectiveness of the kinematics solution and trajectory planning, demonstrating that the improved momentum torque observer can significantly reduce system overshoot, enabling the two-arm surgical robot to perform precise and safe surgical tasks under algorithmic guidance. [ABSTRACT FROM AUTHOR]