Kinematic Differences Research Articles

Strength and activity of the protractor and retractor muscles of the asymptomatic dyskinetic scapula

The role of scapular dyskinesis as a risk factor of shoulder injury has been largely discussed. However, most studies have focused on symptomatic patients and less is known on the asymptomatic dyskinetic scapula. Removing the confounding effects of the pathologies could contribute to better characterize the scapula dyskinesis. As muscle properties (strength, fatigue, nerve injury …) have been identified as causative factors of scapular dyskinesis, this study focuses specifically on characterizing the protractor and retractor muscles of the dyskinetic scapula. Thirteen asymptomatic dyskinetic volunteers were compared to eleven asymptomatic non-dyskinetic control volunteers. Muscle characteristics were evaluated in terms of maximal strength, fatigue resistance and electromyographic activity during a functional closed-chained task. The results did not identify kinematic or muscle activity significant differences between the dyskinetic and the control group even in fatigue conditions. However, the results demonstrated that protractors vs. retractors fatigue resistance ratios were imbalanced (<0.8) in the dyskinetic group and significantly lower than in the non-dyskinetic one. Our study suggests that that strength imbalances are not necessarily related to the presence of pain at the shoulder joint. These results demonstrated the importance to complete the clinical assessments of the scapula with strength evaluations even for asymptomatic sport practitioners.

Wearing an ultrasound probe during walking does not influence lower limb joint kinematics in adolescents with cerebral palsy and typically developing peers

BackgroundEnhancing traditional three-dimensional gait analysis with a portable ultrasound device at the lower-limb muscle-tendon level enables direct measurement of muscle and tendon lengths during walking. However, it is important to consider that the size of the ultrasound probe and its attachment on the lower limb may potentially influence gait pattern. Research questionWhat is the effect of wearing an ultrasound probe at the lower limb in adolescents with cerebral palsy and typically developing peers? MethodsEleven individuals with cerebral palsy and nine age-matched typically developing peers walking barefoot at their self-selected speed were analyzed. Data collection occurred under three conditions: the reference condition (GAIT), and two conditions involving placement of the ultrasound probe over the distal medial gastrocnemius-Achilles tendon junction (MTJ) and over the medial gastrocnemius mid-belly to capture fascicles (FAS). Data processing included calculating differences between conditions using root mean square error (RMSE) for joint kinematics and comparing them to the overall mean difference. Additionally, Spearman correlations were calculated to examine the relationship between kinematic RMSEs and walking speed. ResultsNo significant differences in stance phase duration or walking speed were observed among the three conditions. Average RMSEs were below 5° for all parameters and condition comparisons in both groups. In both the TD and CP groups, RMSE values during the swing phase were higher than those during the stance phase for all joints. No significant correlations were found between height or body mass and swing phase RMSEs. In the CP group, there was a significant correlation between joint kinematics RMSEs and differences in walking speed at the hip, knee and ankle joints when comparing the MTJ condition with the GAIT condition. SignificanceThis study confirms joint kinematics alterations are smaller than 5° due to wearing to the leg an ultrasound probe during walking.

Statistical Parametric Mapping to detect the effects of the secondary jump direction on landing kinematics

ABSTRACT Anterior cruciate ligament (ACL) injuries in sports often occur with non-contact mechanisms, such as landing and cutting. Previous studies explored the ACL injury biomechanical risk factors through drop-jumps combined with secondary jumps. This study aimed to investigate the effect of the secondary jump direction on first landing kinematic temporal series. Fifty-seven participants (29 males, 28 females) performed three single-leg drop-jumps followed by secondary jumps in vertical (single-planar), 45°-medial and 45°-lateral direction (multi-planar). Lower limb and trunk landing kinematics was recorded using a 9-camera motion capture system and analysed with a One-way ANOVA through Statistical Parametric Mapping (SPM), from initial contact to maximum knee flexion. All variables were affected by the secondary jump direction, except trunk rotation. In sagittal plane, kinematic main differences were found between single- and multi-planar tasks. The latter elicited higher trunk, hip, and knee flexion. Frontal plane kinematics was more influenced by medio-lateral components of secondary jumps. Our results could underline how a single task may be insufficient for ACL injury risk assessment. Single- and multi-planar tasks including a secondary jump should be considered for more comprehensive evaluations in prevention and rehabilitation programs, but caution should be used when comparing results of studies adopting different tasks.

Dynamic Gait Analysis in Paediatric Flatfeet: Unveiling Biomechanical Insights for Diagnosis and Treatment.

Flatfeet in children are common, causing concern for parents due to potential symptoms. Technological advances, like 3D foot kinematic analysis, have revolutionized assessment. This review examined 3D assessments in paediatric idiopathic flexible flat feet (FFF). Searches focused on paediatric idiopathic FFF in PubMed, Web of Science, and SCOPUS. Inclusion criteria required 3D kinematic and/or kinetic analysis during posture or locomotion, excluding non-idiopathic cases, adult feet, and studies solely on pedobarography or radiographs. Twenty-four studies met the criteria. Kinematic and kinetic differences between FFF and typical feet during gait were outlined, with frontal plane deviations like hindfoot eversion and forefoot supination, alongside decreased second peak vertical GRF. Dynamic foot classification surpassed static assessments, revealing varied movement patterns within FFF. Associations between gait characteristics and clinical measures like pain symptoms and quality of life were explored. Interventions varied, with orthoses reducing ankle eversion and knee and hip abductor moments during gait, while arthroereisis normalized calcaneal alignment and hindfoot eversion. This review synthesises research on 3D kinematics and kinetics in paediatric idiopathic FFF, offering insights for intervention strategies and further research.

Insight into the Relationship Between Motor and Cognitive Symptoms in Essential Tremor

Essential tremor (ET) is a heterogeneous disorder characterized by bilateral upper limbs action tremor and, possibly, neurological signs of uncertain significance, including voluntary movement abnormalities and cognitive disturbances, i.e., the so-called ‘soft’ signs configuring the ET-plus definition. While motor and cognitive disturbances often coexist in ET, their interrelationship remains largely unexplored. Here we aim to further investigate the relationship between motor symptoms, objectively assessed through kinematic analysis, and cognitive dysfunctions in ET. Seventy ET patients underwent clinical examination, as well as kinematic recordings of tremor and finger tapping and a thorough cognitive assessment. We then tested clinic-demographic and kinematic differences between patients with and without cognitive abnormalities, i.e., with mild cognitive impairment (MCI). Correlation analysis served to explore potential associations between kinematic and cognitive data. Forty-three ET patients (61.42%) had MCI. ET-MCI patients exhibited reduced movement velocity during finger tapping compared to those with normal cognition (p < 0.001). Lower movement velocity during finger tapping was associated with poorer cognitive performance. Namely, we observed a correlation between movement velocity and performance on the Babcock Story Immediate and Delayed Recall Test (r = 0.52 and r = 0.45, both p < 0.001), as well as the interference memory task at 10 and 30 s (r = 0.3, p = 0.008 and r = 0.2, p = 0.03). In this study, we have provided data for a better pathophysiological interpretation of motor and cognitive signs in ET, including the role played by the cerebellum or extra-cerebellar areas, which possibly underpin both signs.

Stroke walking and balance characteristics via principal component analysis

Balance impairment is associated gait dysfunction with several quantitative spatiotemporal gait parameters in patients with stroke. However, the link between balance impairments and joint kinematics during walking remains unclear. Clinical assessments and gait measurements using motion analysis system was conducted in 44 stroke patients. This study utilised principal component analysis to identify key joint kinematics characteristics of patients with stroke during walking using average joint angles of pelvis and bilateral lower limbs in every gait-cycle percentile related to balance impairments. Reconstructed kinematics showed the differences in joint kinematics in both paretic and nonparetic lower limbs that can be distinguished by balance impairment, particularly in the sagittal planes during swing phase. The impaired balance group exhibited greater joint variability in both the paretic and nonparetic limbs in the sagittal plane during entire gait phase and during terminal swing phase respectively compared with those with high balance scores. This study provides a more comprehensive understanding of stroke hemiparesis gait patterns and suggests considering both nonparetic and paretic limb function, as well as bilateral coordination in clinical practice. Principal component analysis can be a useful assessment tool to distinguish differences in balance impairment and dynamic symmetry during gait in patients with stroke.

Heel riser height influence on kinematics and muscle activity of ski mountaineering – A field based study

Introduction The ski binding plays an important role in ski mountaineering. When traveling uphill, the binding has an adjustable heel height known as the riser. Previous laboratory research reported joint kinematics and kinetics are influenced by riser height, however little is known about changes to muscle activity associated with differing joint motion. The purpose of this work was to assess riser height influence on kinematics and muscle activity at different slopes during on-snow skiing. Methods Three female and nine male recreational ski mountaineers (19-26 y) were tested on 5o and 16o gradients using no riser (0 cm) and riser (5.3 cm) at a submaximal 80% HRmax. Each subject used Backland 85 UL skis and Backland Bindings (Atomic Skis, Altenmarkt, Austria). Subjects skied for 6 min at each binding setting with the last 10 gait-cycles evaluating lower limb joint motion gathered from 2D-sagittal plane motion capture. Electromyography (EMG) collected unilaterally on the rectus femoris, biceps femoris, medial gastrocnemius and triceps brachii also. Results 5o slope: hip range of motion (ROM) decreased (p = .003), ankle ROM decreased (p = .005), stride length decreased (p = .004), rating of perceived exertion (RPE) increased (p = .02) for riser compared to no riser. At 16o slope: hip ROM decreased (p = .001), and RPE decreased (p = .004) for riser compared to no riser. HR, glide distance, velocity, EMG, and net mechanical efficiency were not different between riser heights on either slope. Discussion/Conclusion Lower body joint kinematics, step length and RPE varied significantly with riser height. Kinematic differences did not impact velocity or muscle activity when controlling pace. These results agree with previous findings showing minimal differences in EMG and HR while lower body kinematics and RPE changed with riser height.

Chronic ACLD Knees with Early Developmental Cartilage Lesions Exhibited Increased Posterior Tibial Translation during Level Walking.

Early articular cartilage lesion (CL) is a vital sign in the onset of posttraumatic knee osteoarthritis (PTOA) in patients with anterior cruciate ligament deficiency (ACLD). Researchers have suggested that altered kinematics could accelerate CLs and, therefore, lead to the onset of PTOA. However, little is known about whether specific knee kinematics exist that lead to early CL in chronic ACLD knees. Level walking is the most frequent and relevant in vivo activity, which greatly impacts knee health. We hypothesized that the knee kinematics during level walking in chronic ACLD knees with early tibiofemoral CL would significantly differ from those of chronic ACLD knees without early tibiofemoral CL. Thirty patients with a chronic ACLD history, including 18 subjects with CLs and 12 subjects without CLs, and 35 healthy control subjects were recruited for the study from July 2020 to August 2022. The knee kinematic data during level walking were collected using a three-dimensional motion analysis system. The kinematic differences between groups were compared using statistical parametric mapping with one dimension for One-Way ANOVA. The cartilage statuses of the ACLD knees were assessed via MRI examination. The CLs distribution of subjects was evaluated using a modified Noyes scale and analyzed by chi-square tests. ACLD knees with CLs had significantly greater posterior tibial translation (7.7-8.0mm, 12%-18% gait cycle GC, p = 0.014) compared to ACLD knees without CLs during level walking. ACLD knees with CLs had greater posterior tibial translation (4.6-5.5mm, 0%-23% GC, p < 0.001; 5.8-8.0mm, 86%-100% GC, p < 0.001) than healthy controls during level walking. In the group of ACLD knees with CLs, CL is mainly located in the back of the tibia plateau and front of load bearing area of the medial femoral condyle (p < 0.05). Chronic anterior cruciate ligament deficient knees with cartilage lesions have increased posterior tibial translation compared to anterior cruciate ligament deficient knees without cartilage lesions and healthy subjects. The posterior tibial translation may play an important role in knee cartilage degeneration in ACLD knees. The increased posterior tibial translation and cartilage lesion characteristics may improve our understanding of the role of knee kinematics in cartilage degeneration and could be a helpful potential reference for anterior cruciate ligament deficient therapy, such as physical training to improve abnormal kinematic behavior.

Effects of the open Latarjet procedure on shoulder kinematics and periscapular muscle activity 3 months postoperatively

BackgroundThe debate surrounding the influence of the open Latarjet procedure on postoperative scapular motions persists, and there is no evidence regarding its effects on periscapular muscle activation. This study aimed to assess the short-term influence of open Latarjet procedure on scapular kinematics and periscapular muscle activity during arm raising and lowering based on comparisons between patient and healthy athletes. Methods22 healthy male athletes and 22 male athletes scheduled for glenohumeral stabilization surgery by open Latarjet procedure were included. Scapular kinematics, periscapular muscle activities and shoulder-related quality of life were recorded prior to surgery and 3 months postoperatively for the Latarjet group. For the healthy group, same assessments were performed 3 months apart. Bilateral differences in both scapular kinematics and periscapular muscle activation ratios, and Western Ontario Shoulder Instability (WOSI) index were defined as dependent variables. ResultsScapular kinematics of the operated shoulder, namely scapular upward/downward rotation, internal/external rotation and anterior/posterior tilt recorded between 20° and 120° of humerothoracic elevation, showed no alterations 3 months post-surgery (p>0.05), and did not differ from those observed in healthy athletes (p>0.05). Similarly, all periscapular muscle activations were not different within time and between groups (p>0.05). WOSI index of the operated shoulder was significantly improved postoperatively (871.9 ± 443.7 vs. 1346.3 ± 552.3) but remained higher than the WOSI indices of the non-operated shoulder or those of the healthy group (52.7±75.6). ConclusionThis study emphasizes the short-term effects of the open Latarjet procedure, demonstrating an improvement in the shoulder-related quality of life 3 months after surgery. Notably, during this period, both kinematics and periscapular muscle activity remained consistent, and similar to the patterns observed for healthy athletes.

A Biomechanical Comparison of the Back Squat and Hexagonal Barbell Deadlift.

Stahl, CA, Regni, G, Tanguay, J, McElfresh, M, Trihy, E, Diggin, D, and King, DL. A biomechanical comparison of the back squat and hexagonal barbell deadlift. J Strength Cond Res 38(5): 815-824, 2024-Coaches often use different exercises to encourage similar strength adaptations and limit monotony. Anecdotally, the hexagonal barbell deadlift (HBD) exhibits similarities to the back squat (BS). To date, research has not examined the empirical differences between these exercises. This study examined kinematic and kinetic differences between the BS and the HBD across different loads. Sixteen resistance-trained individuals (6 men and 10 women) volunteered to participate. Subjects performed 1-repetition maximum (1RM) testing under BS and HBD conditions. Kinematic and kinetic data were collected during performance of both exercises at submaximal (warm-up sets) and maximal (1RM) loads using a 3D motion capture and force-plate system. Results showed that subjects lifted greater 1RM loads in the HBD relative to the BS (p < 0.05; d = -1.75). Kinematic data indicated that subjects exhibited greater maximum forward lean of the trunk and decreased maximum knee flexion while performing the HBD compared with the BS. The BS resulted in higher maximum extension moments at the hip joint than the HBD. Maximum extension moments at the knee joint showed no difference between the exercises. Data suggest that bar design and position facilitate balanced moment arm length at hip and knee joints during performance of the HBD. By contrast, bar position during performance of the BS increases moment arm length at the hip joint, making it a hip-dominant exercise. The present data have implications for the programming of both exercises. Future research should examine differences in muscle-activation strategies between the 2 exercises.

Reduced trunk movement control during motor dual-tasking in older adults

Older adults have a decreased trunk movement control which is linked to their higher fall risk. While motor/cognitive dual-tasking deteriorates balance and walking in older adults, there is limited understanding on how trunk kinematics and kinetics are affected by dual-tasking in scenarios where falls can occur. Therefore, the purpose of the study was to determine the impacts of a challenging motor dual-task, specifically obstacle avoidance during walking, on trunk and lower-body kinematics and kinetics of older adults compared to young adults. The study captured three-dimensional kinematic and kinetic data from 12 young adults and 10 older adults as they walked on a treadmill and stepped over an obstacle with both legs. The study analyzed trunk, hip, knee, and ankle angles and torques. Trunk torque was further broken down to trunk muscle torque, gravitational torque, and inertia torque. A linear mixed effects model was used to investigate the difference in each variable between the two groups. Older adults exhibited significantly increased trunk flexion angle and trunk extension muscle torque compared to young adults, with the trunk being the only segment/joint showing differences in both kinematics and kinetics. Trunk torque breakdown analysis revealed that larger trunk flexion led to a larger gravitational torque, which contributed to an increased compensatory trunk muscle torque. Moreover, older adults' less controlled trunk flexion during weight shifting from trail leg to the lead leg, necessitated a compensatory trunk deceleration during trail leg obstacle avoidance which was achieved by generating additional increase in trunk muscle torque. The study demonstrated that motor dual-tasking has the most negative effects on trunk control in older adults compared to young adults. This exposes older adults to a higher fall risk. Therefore, future work should focus on supporting trunk control during daily multi-tasking conditions where falls can occur.

Biomechanical Analyses of Scoop in Field Hockey

Field hockey is an Olympic sport played all over the world. Hockey is played with a stick where one requires endurance, agility, balance coordination, and high skill to convert the shot. There are various kinds of skills i.e. hitting, dribbling, scooping, tackling etc. Only scoop was selected for the study in different phases (stance phase, execution phase, follow through phase). Field hockey scoop is the aerial passing by lifting the ball from the ground inserting head of hockey stick under the ball. Scoop plays vital role in competitive field hockey games. The aim of the study was to find out the kinematic difference in the elbow joint, knee joint, and ankle joint. The objective of the study was to find out the angular differences of elbow joint, knee joint, and ankle joint in different phases of delivery of field hockey scoop shot. Researchers hypothesised that there are significance differences in elbow joint angle, knee joint angle, and ankle joint angle during delivering of field hockey scoop shot. Six males inter university players aged from 20-24 years were selected for the study and at least they represented at inter university games /national level. Set of the camera is at 1.10 m in height and 3.70 meters. The focal length is 5.6, the resolution is 1080, and the frame rate is 100 per sec. A Sony FRD-AX700 camera was placed 3.7 meters apart on the right side of the hockey player. Angle of elbow joint, angle of knee joint, angle ankle joint, cadence, stride length, and numbers of frames were analysed using Kinovea 0.9.5 software. This research will help the players to execute scoop after knowing elbow joint angle, knee joint angle, and ankle joint angle. Key Words: Field Hockey, Scoop, Elbow, Ankle, Knee.

Hindfoot kinematics and kinetics - A combined in vivo and in silico analysis approach

BackgroundThe complex anatomical structure of the foot-ankle imposes challenges to accurately quantify detailed hindfoot kinematics and estimate musculoskeletal loading parameters. Most systems used to capture or estimate dynamic joint function oversimplify the anatomical structure by reducing its complexity. Research QuestionCan four dimensional computed tomography (4D CT) imaging in combination with an innovative foot manipulator capture in vivo hindfoot kinematics during a simulated stance phase of walking and can talocrural and subtalar articular joint mechanics be estimated based on a detailed in silico musculoskeletal foot-ankle model. MethodsA foot manipulator imposed plantar/dorsiflexion and inversion/eversion representing a healthy stance phase of gait in 12 healthy participants while simultaneously acquiring 4D CT images. Participant-specific 3D hindfoot rotations and translations were calculated based on bone-specific anatomical coordinate systems. Articular cartilage contact area and contact pressure of the talocrural and subtalar joints were estimated using an extended foot-ankle model updated with an elastic foundation contact model upon prescribing the participant-specific rotations measured in the 4D CT measurement. ResultsPlantar/dorsiflexion predominantly occurred at the talocrural joint (RoM 15.9±3.9°), while inversion/eversion (RoM 5.9±3.9°) occurred mostly at the subtalar joint, with the contact area being larger at the subtalar than at the talocrural joint. Contact pressure was evenly distributed between the talocrural and subtalar joint at the beginning of the simulated stance phase but was then redistributed from the talocrural to the subtalar joint with increasing dorsiflexion. SignificanceIn a clinical case study, the healthy participants were compared with four patients after surgically treaded intra-articular calcaneal fracture. The proposed workflow was able to detect small but meaningful differences in hindfoot kinematics and kinetics, indicative of remaining hindfoot pathomechanics that may influence the onset and progression of degenerative joint diseases.

Effects of different step lengths at a preferred walking speed on forefoot, midfoot, and hindfoot motion in healthy young adults

Hindfoot, midfoot, and forefoot motion during the stance phase of walking provide insights into the forward progression of the body over the feet via the rocker mechanisms. These segmental motions are affected by walking speed. Increases in walking speed are accomplished by increasing step length and cadence. It is unknown if taking short, medium, and long steps at the same speed would increase hindfoot, midfoot, and forefoot motion similarly to walking speed. We examined effects of different step lengths at the same preferred walking speed on peak forefoot, midfoot, and hindfoot motions related to the foot rockers. Twelve young healthy adults completed five walking trials under three step length conditions in a random order as feet and lower extremity motion were measured via marker positions for the combined Oxford foot and conventional gait models. Peak hindfoot, midfoot, and forefoot joint angles indicating heel, ankle, and forefoot rockers were identified. When walking at the same preferred speed with increase in step length, there were increases in peak hindfoot-tibia plantarflexion angle (p < 0.001; ηp2 = 0.76) in early stance associated with the heel rocker and peak hindfoot-tibia dorsiflexion angle (p = 0.016; ηp2 = 0.39) in midstance associated with ankle rocker. In late stance, the peak hindfoot-tibia plantarflexion angle, forefoot-hindfoot angle, and forefoot-hallux dorsiflexion angle indicating forefoot rocker motion also increased with step length (p < 0.01). When foot kinematics are compared across different individuals or the same individual across different sessions, researchers and clinicians should consider the influence of step length as a contributor to differences in foot kinematics observed.

REAL-TIME WATER LEVEL MONITORING USING LOW-COST GNSS RECEIVER

Abstract. Developing an accurate water level monitoring system is one of the measures to mitigate the effects of water-related hazards such as river flooding. While current monitoring systems in the country are efficient in terms of accurate and immediate data delivery, these systems can be costly. This study assesses the Global Navigation Satellite System (GNSS) performance of low-cost receiver systems for water level monitoring using real-time kinematic (RTK) solution. A total of 10 days’ valid observation were analyzed to compare the two base-rover receiver setups: 1) low-cost base to low-cost rover (LC-LC) and 2) survey-grade base to low-cost rover (SG-LC) grounded on accuracy, integrity, continuity, availability, and cost. Accuracy results show LC-LC=5.81 cm and SG-LC=5.37 cm mean difference of RTK from in-situ readings. In terms of RTK and post-processing kinematic (PPK) difference for integrity criterion, the RTK SG-LC setup has a lower range of RMS of 0.86 to 1.94 cm versus LC-LC setup of 1.19 to 2.28 cm. For the continuity criterion, the average fixed solutions percentage for the LC-LC setup: RTK=91.43%, PPK=92.92%, whereas for the SG-LC: RTK=95.51%, PPK=98.39%. On availability, the number of valid satellites (NSat) and position dilution of precision (PDOP) of RTK and PPK solutions for each setup are LC-LC: RTK=11, PPK=23, PDOP=1.0 and SG-LC: RTK=11, PPK=24, PDOP=1.9. Lastly, in terms of costing, LC-LC costs Php 58,340 while SG-LC costs Php 1,279,645. Overall, the parity of LC-LC with SG-LC in terms of the five criteria suggests viability of using LC-LC for accurate real-time water level monitoring.

Jump Landing Kinematics: Establishing Normative Ranges For Male And Female Athletes.

Lower extremity joint (LE) kinematics during landing tasks are important predictors of injury risk and performance outcomes in athletes. To establish sex-related differences and normative ranges for LE kinematics during the jump-landing task in a large cohort of healthy military service academy cadets. Cross-Sectional Study. US Air Force, Naval, and Military Academies. 5308 cadets (2062 females [38.8%]). Sex-related differences in LE kinematics were analyzed using independent samples t-tests. Mean differences (MD) and effect sizes (d) were reported for interpretability. Normative ranges for hip and knee joint angles were established separately for males and females at initial contact (IC) and 50% of the stance phase. Compared to males, moderate effect sizes (d ≥ .5) were observed for knee external rotation (negative value) where females displayed greater motion at IC and at 50% stance (MD: - 3.9˚ and -5.0˚, respectively, p < .001). The following findings were of small effect size (.2 ≥ d > .5). Females exhibited less knee and hip flexion at IC (MD: -1.8˚ and -0.5˚, respectively, p < .001) and at 50% stance (MD: -4.1˚ and -4.6˚, respectfully, p < .001). This was accompanied by females having greater knee valgus (negative value) and hip adduction at IC (MD: -2.2˚ and 1.06˚, respectively, p < .001) and at 50% stance (MD: -3.2˚ and 1.8˚, respectfully, p < .001). This study establishes normative ranges for LE kinematics during the jump-landing task in a large cohort of healthy military service academy cadets entering their first year. Sex- related differences in LE kinematics were observed, highlighting the importance of considering sex as a factor in the evaluation of lower extremity movement quality and management of injury risk.

Symmetry and synchrony of bimanual movements are not predicated on interlimb control coupling.

Previous studies suggest that bimanual coordination recruits neural mechanisms that explicitly couple control of the arms, resulting in symmetric kinematics. However, the higher symmetry for actions that require congruous joint motions compared with noncongruous joint motions calls into question the concept of control coupling as a general policy. An alternative view proposes that codependence might emerge from an optimal feedback controller that minimizes control effort and costs in task performance. Support for this view comes from studies comparing conditions in which both hands move a shared or independent virtual objects. Because these studies have mainly focused on congruous bimanual movements, it remains unclear if kinematic symmetry emerges from such control policies. We now examine movements with congruous or noncongruous joint motions (inertially symmetric or asymmetric, respectively) under shared or independent cursors conditions. We reasoned that if a control policy minimizes kinematic differences between limbs, spatiotemporal symmetry should remain relatively unaffected by inertial asymmetries. As shared tasks reportedly elicit greater interlimb codependence, these conditions should elicit higher bilateral covariance regardless of inertial asymmetries. Our results indicate a robust spatiotemporal symmetry only under inertially symmetric conditions, regardless of cursor condition. We simulated bimanual reaching using an optimal feedback controller with and without explicit costs of kinematic asymmetry, finding that only the latter mirrored our empirical data. Our findings support the hypothesis that bimanual control policies do not include kinematic asymmetry as a cost when it is not demanded by task constraints suggesting that kinematic symmetry depends critically on mechanical movement conditions.NEW & NOTEWORTHY Previously, the control coupling hypothesis and task-dependent control hypothesis have been shown to be robust in the bimanually symmetrical movement, but whether the same policy remains robust in the bimanually asymmetrical movement remains unclear. Here, with evidence from empirical and simulation data, we show that a spatiotemporal symmetry between the arms is not predicated on control coupling, but instead it is predicated on the symmetry of mechanical conditions (e.g. limb inertia) between the arms.

Comparison of glenohumeral and scapulothoracic kinematics between fastballs and curveballs during baseball pitching

ABSTRACT Shoulder injuries are common in baseball pitchers and primarily involve the glenohumeral joint. Past analyses have examined shoulder biomechanics during different pitch types simply as the motion of the upper arm relative to the thorax. In this study, glenohumeral and scapulothoracic kinematics were compared between fastballs and curveballs at key timepoints throughout a pitch. Upper extremity kinematics of thirteen collegiate pitchers were collected during fastball and curveball pitches with motion capture. A linear model approach was utilised to estimate scapular kinematics based on measurable humerothoracic motion. Glenohumeral kinematics were computed from the scapular and humeral motion data. Comparisons of scapulothoracic and glenohumeral kinematic variables at times of maximum glenohumeral external rotation, ball release, and maximum glenohumeral internal rotation between pitch types were made using paired t-tests with Benjamini-Hochberg corrections. There were no significant differences in glenohumeral kinematics. Fastballs elicited significantly less scapulothoracic internal rotation and more posterior tilt at maximum glenohumeral external rotation. Fastballs produced significantly less scapulothoracic internal rotation and anterior tilt at maximum glenohumeral internal rotation. This study provides further evidence that risk of injury to the glenohumeral joint may be consistent between fastballs and curveballs and offers insights into subtle differences in scapular kinematics between pitch types.

Ankle Muscle Strength and Gait Function After Dorsal Closing Wedge Calcaneal Osteotomy for Haglund Exostosis-Related Heel Pain.

Haglund exostosis-related heel pain may be surgically treated with dorsal closing wedge calcaneal osteotomy (DCWCO). Recent reports on this technique show good clinical and self-reported outcomes. However, uncertainty about functional consequences related to ankle muscle strength and gait function due to a shortened Achilles tendon lever arm exists. Fifteen patients (15 feet) with Haglund exostosis-related heel pain were surgically treated with DCWCO and evaluated before and 1 year after surgery. Isometric plantar flexion and dorsiflexion strength was quantified for both the involved and the uninvolved limb. Gait analysis was performed at a self-selected walking speed using a 3D motion capture system including force plates. Self-reported outcomes (Foot Function Index and Global Treatment Outcome) were also assessed. Before surgery, as well as after surgery, plantar flexion strength of the involved limb was significantly lower compared to the uninvolved limb while dorsiflexion strength did not differ between limbs at both time points. Step length and time, ankle flexion angles, power generation, and propulsive impulses during gait did not differ between limbs both before and after surgery. Propulsive impulse and step length of the involved limb increased from pre- to postsurgery with an effect size of 1.04 and 0.48, respectively, revealing a general improvement in gait dynamics. Total Foot Function Index improved by 48% after surgery, and 80% of patients rated their surgery as "helped" or "helped a lot" (Global Treatment Outcome). In this relatively small cohort, we found that patients treated for Haglund exostosis-related heel pain with DCWCO surgery had minor interlimb differences in gait kinematics and kinetics and generally improved gait dynamics and self-reported function at 1-year follow-up. Level II, observational prospective cohort study.

Is increased trunk flexion in standing up related to muscle weakness or pain avoidance in individuals with unilateral knee pain; a simulation study.

The 'Timed Up and Go' test (TUG) is a widely used clinical tool for assessing gait and balance, relying primarily on timing as a measure. However, there are more observable biomechanical compensation strategies within TUG that are indicative of underlying neuromuscular issues and movement priorities. In individuals with unilateral knee osteoarthritis, an increased trunk flexion during TUG is a common phenomenon, often attributed to muscle weakness and/or pain avoidance. Unfortunately, it is difficult to differentiate between these underlying causes using experimental studies alone. This study aimed to distinguish between muscle weakness and pain avoidance as contributing factors, using predictive neuromuscular simulations of the sit-to-walk movement. Muscle weakness was simulated by reducing the maximum isometric force of the vasti muscles (ranging from 20% to 60%), while pain avoidance was integrated as a movement objective, ensuring that peak knee load did not exceed predefined thresholds (2-4times body weight). The simulations demonstrate that a decrease in muscular capacity led to greater trunk flexion, while pain avoidance led to slower movement speeds and altered muscle recruitments, but not to greater trunk flexion. Our predictive simulations thus indicate that increased trunk flexion is more likely the result of lack of muscular reserve rather than pain avoidance. These findings align with reported differences in kinematics and muscle activations between moderate and severe knee osteoarthritis patients, emphasizing the impact of severe muscle weakness in those with advanced knee osteoarthritis. The simulations offer valuable insights into the mechanisms behind altered movement strategies, potentially guiding more targeted treatment.