Head Stabilization Research Articles

Simultaneous Localization and Mapping Methods for Snake-like Robots Based on Gait Adjustment.

Snake robots require autonomous localization and mapping capabilities for field applications. However, the characteristics of their motion, such as large turning angles and fast rotation speeds, can lead to issues like drift or even failure in positioning and map building. In response to this situation, this paper starts from the gait motion characteristics of the snake robot itself, proposing an improved gait motion method and a tightly coupled method based on IMU and visual information to solve the problem of poor algorithm convergence caused by head-shaking in snake robot SLAM. Firstly, the adaptability of several typical gaits of the snake robot to SLAM methods was evaluated. Secondly, the serpentine gait was selected as the object of gait improvement, and a head stability control method for the snake robot was proposed, thereby reducing the interference of the snake robot's motion on the sensors. Thirdly, a visual-inertial tightly coupled SLAM method for the snake robot's serpentine gait and Arc-Rolling gait was proposed, and the method was verified to enhance the robustness of the visual SLAM algorithm and improve the positioning and mapping accuracy of the snake robot. Finally, experiments proved that the methods proposed in this paper can effectively improve the accuracy of positioning and map building for snake robots.

Evaluating the clinical potential of bioceramic-rods for revascularization in osteonecrosis of the femoral head: a systematic review.

To evaluate the safety, reliability, and effectiveness of bioceramic rods (BR) in treating osteonecrosis of the femoral head (ONFH), compared with other treatments such as core decompression and autologous bone grafting. Systematic review and meta-analysis. Pubmed, Embase, and CNKI databases from January 2011 to July 2023. Included studies involved patients treated with bioceramic rods. Studies were required to have a follow-up time of more than six months and no statistically significant differences in baseline information between groups in controlled studies. Exclusions included literature reviews, case reports, conference abstracts, animal experiments, and studies without defined success criteria or lacking analysis on factors influencing efficacy. The primary outcome measure was the Harris Hip Score (HHS) improvement rate. Secondary outcomes included the femoral head stability and survival rate, alongside the hip replacement rate. The systematic review revealed significant improvements in symptom relief and functional recovery using BR for the treatment of ONFH. An average follow-up of 20.44 months showed an overall HHS improvement rate of 33.93%. Hip preservation efficacy with BR was superior to core decompression and autologous bone grafting. The overall femoral head survival rate was 84.42%, with results sustained for three years. The success rate of hip preservation was notably higher with early intervention, which showed better outcomes when the overall HHS improvement exceeded 27%, and rates of excellent and good outcomes approached 90%. Bioceramic rods offer a safe, minimally invasive, reliable, and effective treatment option for ONFH, ensuring substantial symptom relief and functional recovery. The technique's success in early disease stages suggests a strong potential for broader clinical adoption. Although additional benefits from combining BR with stem cells, platelet-rich plasma, and traditional Chinese medicine are noted, definitive conclusions on enhanced therapeutic effects remain inconclusive.

NeuroMechFly v2: simulating embodied sensorimotor control in adult Drosophila.

Discovering principles underlying the control of animal behavior requires a tight dialogue between experiments and neuromechanical models. Such models have primarily been used to investigate motor control with less emphasis on how the brain and motor systems work together during hierarchical sensorimotor control. NeuroMechFly v2 expands Drosophila neuromechanical modeling by enabling vision, olfaction, ascending motor feedback and complex terrains that can be navigated using leg adhesion. We illustrate its capabilities by constructing biologically inspired controllers that use ascending feedback to perform path integration and head stabilization. After adding vision and olfaction, we train a controller using reinforcement learning to perform a multimodal navigation task. Finally, we illustrate more bio-realistic modeling involving complex odor plume navigation, and fly-fly following using a connectome-constrained visual network. NeuroMechFly can be used to accelerate the discovery of explanatory models of the nervous system and to develop machine learning-based controllers for autonomous artificial agents and robots.

Exploratory Investigation of Head Stability in Children with Cerebral Palsy and Typically Developing Children during a Targeted Stepping Task

Children with cerebral palsy (CP) exhibit head instability during simple overground walking, which may comprise sensory input and reduce stepping accuracy. Investigations of head stability during more challenging tasks, where fall risk may be increased, are limited. This study explored differences in head stability between ambulatory children with hemiplegic CP (N = 9) and diplegia (N = 9) (GMFCS I and II) and typically developing (TD) children (N = 8) during a targeted stepping task. All children completed five trials stepping into two successive rectangular floor-based targets whilst walking along an 8 m walkway. Three-dimensional motion capture enabled calculation of head stability and foot placement within and before each target. A two-way mixed-design ANOVA compared differences between all groups and target approach. Children with diplegic CP showed greater sagittal, frontal, and resultant head-to-laboratory and head-to-trunk head instability compared to children with hemiplegic CP and TD children. Anteroposterior foot placement error was significantly greater in children with hemiplegic CP (8.5 ± 5.0 cm) compared to TD children (3.8 ± 1.5 cm). Group differences in head instability were not consistent with group differences in foot placement error. To better understand how head instability might affect fall risk in children with CP, more challenging environments should be tested in future.

Quantifying toddler exploration in different postures with powered mobility

ABSTRACT Access to powered mobility can support play and development for toddlers with disabilities. Using powered mobility in a standing posture has been theorized to support development of muscle coordination, balance, head and trunk stability, and transition to ambulation. The purpose of this study was to quantify and characterize joystick control, bodyweight support, and muscle activity while using the Permobil Explorer Mini in seated and supported standing postures. Nine children with mobility disabilities participated in four visits where they completed two, 15–20 minute play sessions, one in each posture, with a break between. We found that all toddlers engaged with the joystick in both postures, with individual differences in favored directions and control patterns. Participants had similar loading through their feet in both postures, but had slightly higher muscle activity in standing, especially while driving. These results demonstrate that young children with disabilities quickly engage with joystick-based powered mobility in seated and standing postures, with important individual differences that can inform future design of devices and interventions to support play and development.

Human proprioceptive gaze stabilization during passive body rotations underneath a fixed head

The present study explored the presence of torsional gaze-stabilization to proprioceptive neck activation in humans. Thirteen healthy subjects (6 female, mean age 25) were exposed to passive body rotations while maintaining a head-fixed, gravitationally upright, position. Participants were seated in a mechanical sled, their heads placed in a chin rest embedded in a wooden beam while wearing an eye tracker attached to the beam using strong rubber bands to ensure head stability. The body was passively rotated underneath the head both in darkness and while viewing a projected visual scene. Static torsional gaze positions were compared between the baseline position prior to the stimulation, and immediately after the final body tilt had been reached. Results showed that passive neck flexion produced ocular torsion when combined with a visual background. The eyes exhibited rotations in the opposite direction of the neck’s extension, matching a hypothetical head tilt in the same direction as the sled. This corresponded with a predicted head rotation aimed at straightening the head in relation to the body. No such response was seen during trials in darkness. Altogether, these findings suggest that proprioception may produce a predictive gaze-stabilizing response in humans.

Influence of aging on the relation between head control and hip joint kinematics during crossover stepping.

Falls in older individuals are a serious health issue in super-aged societies. The stepping reaction is an important postural strategy for preventing falls. This study aimed to reveal the characteristics of lateral stepping in response to mechanical disturbance by means of an analysis of the hip joint kinematics in the stepping leg and head stability during crossover steps. The participants included 11 healthy older and 13 younger individuals. An electromagnet-controlled disturbance-loading device induced crossover steps due to lateral disturbance. Responses were measured using a motion capture system and force plates. The righting reaction of the head was quantified by lateral displacement (sway), neck joint kinematics (angle displacement, angular velocity), and neck joint moment during crossover stepping. Moreover, the relationship between the neck lateral bending moment and angular velocity of hip flexion/adduction of the stepping leg was examined. The lateral head sway was significantly larger in the older participants (1.13±0.7 m/s2) than in the younger individuals (0.54±0.3 m/s2); whereas, the angle displacement (older -14.1±7.1 degree, young -8.3±4.5 degree) and angular velocity (older 9.9±6.6 degree/s, 41.2±27.7 degree/s) of the head were significantly lower in the older than in the younger participants. In both groups, the moment of neck lateral bending exhibited a significant negative correlation with the hip flexion angular velocity of the stepping leg. Correlation analysis also showed a significant negative correlation between the neck lateral bending moment and hip adduction angular velocity only in the older group (r = 0.71, p<0.01). In conclusion, older individuals increased instability in the lateral direction of the head and decreased righting angle displacement and angular velocity of the head during crossover steps. The correlation between neck moment and hip flexion/adduction angular velocity suggested a decrease in step speed due to increased neck muscle tone, which could be influenced by vestibulospinal reflexes.

Full-body kinematics and head stabilisation strategies during walking in patients with chronic unilateral and bilateral vestibulopathy

Chronic imbalance is a frequent and limiting symptom of patients with chronic unilateral and bilateral vestibulopathy. A full-body kinematic analysis of the movement of patients with vestibulopathy would provide a better understanding of the impact of the pathology on dynamic tasks such as walking. Therefore, this study aimed to investigate the global body movement during walking, its variability (assessed with the GaitSD), and the strategies to stabilise the head (assessed with the head Anchoring Index). The full-body motion capture data of 10 patients with bilateral vestibulopathy (BV), 10 patients with unilateral vestibulopathy (UV), and 10 healthy subjects (HS) walking at several speeds (slow, comfortable, and fast) were analysed in this prospective cohort study. We observed only a few significant differences between groups in parts of the gait cycle (shoulder abduction–adduction, pelvis rotation, and hip flexion–extension) during the analysis of kinematic curves. Only BV patients had significantly higher gait variability (GaitSD) for all three walking speeds. Head stabilisation strategies depended on the plan of motion and walking speed condition, but BV and UV patients tended to stabilise their head in relation to the trunk and HS tended to stabilise their head in space. These results suggest that GaitSD could be a relevant biomarker of chronic instability in BV and that the head Anchoring Index tends to confirm clinical observations of abnormal head-trunk dynamics in patients with vestibulopathy while walking.

Applying Resistant Starch to Improve the Gel and Water Retention of Reduced-Fat Pork Batter.

Emulsified meat products contain high animal fat content, and excessive intake of animal fat is not good for health, so people are paying more and more attention to reduced-fat meat products. This study investigated the impact of varying proportions of pork back-fat and/or resistant starch on the proximate composition, water and fat retention, texture properties, color, and rheology characteristic of pork batter. The results found that replacing pork back-fat with resistant starch and ice water significantly decreased the total lipid and energy contents of cooked pork batter (p < 0.05) while improving emulsion stability, cooking yield, texture, and rheology properties. Additionally, when the pork back-fat replacement ratio was no more than 50%, there was a significant increase in emulsion stability, cooking yield, hardiness, springiness, cohesiveness, chewiness, and L* and G' values (p < 0.05). Furthermore, resistant starch and ice water enhanced myosin head and tail thermal stability and increased G' value at 80 °C. However, the initial relaxation times significantly decreased (p < 0.05) and the peak ratio of P21 significantly increased from 84.62% to 94.03%, suggesting reduced fluidity of water. In conclusion, it is feasible to use resistant starch and ice water as a substitute for pork back-fat in order to produce reduced-fat pork batter with favorable gel and rheology properties.

Humanoid Head Camera Stabilization Using a Soft Robotic Neck and a Robust Fractional Order Controller.

In this paper, a new approach for head camera stabilization of a humanoid robot head is proposed, based on a bio-inspired soft neck. During walking, the sensors located on the humanoid's head (cameras or inertial measurement units) show disturbances caused by the torso inclination changes inherent to this process. This is currently solved by a software correction of the measurement, or by a mechanical correction by motion cancellation. Instead, we propose a novel mechanical correction, based on strategies observed in different animals, by means of a soft neck, which is used to provide more natural and compliant head movements. Since the neck presents a complex kinematic model and nonlinear behavior due to its soft nature, the approach requires a robust control solution. Two different control approaches are addressed: a classical PID controller and a fractional order controller. For the validation of the control approaches, an extensive set of experiments is performed, including real movements of the humanoid, different head loading conditions or transient disturbances. The results show the superiority of the fractional order control approach, which provides higher robustness and performance.

236 Bilateral Intrathalamic Infusion of rAAVrh8-Hexa/Hexb in a Phase 1/2 Clinical Trial for Gene Therapy in Infantile and Juvenile Tay-Sachs and Sandhoff Disease; Surgical Technique

INTRODUCTION: Tay-Sachs (TSD) and Sandhoff (SD) diseases are rare,monogenic and severe neurodegenerative disorders due to Hexosaminidase A deficiency. We performed the first-in-human bilateral thalamic (BiTh) delivery of rAAVrh8-HEXA/HEXB in 8 children in a Phase 1/2 clinical trial. METHODS: Stereotactic infusion cannula placement was performed using ROSA robotic platform. Bilateral trajectories were planned via the trans-frontal route..Head stabilization was accomplished using radiolucent horse-shoe head rest and radiolucent pin-skull clamps. Flexible infusion cannulas were placed through small drill holes using ROSA guidance. Cannula stabilization was achieved using a construct which combined the Navigus brain biopsy platform and flexible cannula bolt. Insertion accuracy was verified with intraoperative CT images. Patients received one of the three doses in each thalamus: 180 mcl (5.87E + 12vg), 360 mcl (1.17E + 13vg) or 720 mcl (2.35E + 13vg). Drug infusion rate was 4 mcl/minute and completed in 90-360 minutes depending on drug dosage. RESULTS: Eight patients received treatment; 5 infants (6, 11, 13, 17, and 20 months) and 3 juvenile (5, 6, 12 years). Duration of follow up was 2-28 months. Outcome assessments included safety, CSF biochemistry, MRI/MRS/DTI, and neurodevelopmental observations. Surgery and drug infusions were well-tolerated. Post-infusion MRIs showed signal enhancement volume coverage in thalamus from 8%-44% parallel to escalating doses. The only surgery related complication was superficial wound dehiscence in two patients. Infants showed partial stabilization or improvement, including in oral feeding and myelination. In juveniles, dystonic posturing worsened after dosing in all 3 patients treated. Two patients died much later from reasons unrelated to surgery or drug infusion. CONCLUSIONS: Surgery for BiTh infusion of rAAVrh8-HEXA/HEXB for gene therapy in infants with TSD and SD is well-tolerated. Patients respond well to treatment with some stabilization or improvement.

Auditory and Visual Gratings Elicit Distinct Gamma Responses.

Sensory stimulation is often accompanied by fluctuations at high frequencies (>30 Hz) in brain signals. These could be "narrowband" oscillations in the gamma band (30-70 Hz) or nonoscillatory "broadband" high-gamma (70-150 Hz) activity. Narrowband gamma oscillations, which are induced by presenting some visual stimuli such as gratings and have been shown to weaken with healthy aging and the onset of Alzheimer's disease, hold promise as potential biomarkers. However, since delivering visual stimuli is cumbersome as it requires head stabilization for eye tracking, an equivalent auditory paradigm could be useful. Although simple auditory stimuli have been shown to produce high-gamma activity, whether specific auditory stimuli can also produce narrowband gamma oscillations is unknown. We tested whether auditory ripple stimuli, which are considered an analog to visual gratings, could elicit narrowband oscillations in auditory areas. We recorded 64-channel electroencephalogram from male and female (18 each) subjects while they either fixated on the monitor while passively viewing static visual gratings or listened to stationary and moving ripples, played using loudspeakers, with their eyes open or closed. We found that while visual gratings induced narrowband gamma oscillations with suppression in the alpha band (8-12 Hz), auditory ripples did not produce narrowband gamma but instead elicited very strong broadband high-gamma response and suppression in the beta band (14-26 Hz). Even though we used equivalent stimuli in both modalities, our findings indicate that the underlying neuronal circuitry may not share ubiquitous strategies for stimulus processing.

Effects of humeral head stabilization intervention during aggressive manual passive stretching exercises in patients with painful stiff shoulder: a prospective, comparative study

BackgroundNo reports have been published verifying the effects of manual interventions such as humeral head stabilization on improving function and reducing pain when applying aggressive manual passive stretching in patients with painful stiff shoulders. The purpose of this study was to compare clinical outcomes, such as range of motion (ROM), pain, and disability scores, in patients with painful stiff shoulders with and without humeral head stabilization intervention while applying aggressive manual passive stretching. MethodsFifty-six patients with painful stiff shoulders were recruited (31 with humeral head stabilization intervention and 25 without such intervention). Clinical outcomes such as active ROM (A-ROM), pain, and disability scores were evaluated using a goniometer; measurement of activity visual analog scale (A-VAS); and disabilities of the arm, shoulder and hand (DASH) and shoulder pain and disability index (SPADI), respectively. ResultsAll the parameters, A-ROM, A-VAS, and disability scores (DASH and SPADI) were not significantly different between the two groups (p > 0.05) before the intervention. However, after the intervention, the mean difference in A-ROM for flexion, abduction, and external and internal rotation was 18 (95% confidence interval [CI], 14.1 to 21.7), 31 (95% CI, 24.9 to 37.4), 17 (95% CI, 13.4 to 21.4), and 16 (95% CI, 11.6 to 20.9), respectively. The mean difference in A-VAS and disability scores for DASH and SPADI was -1 (95% CI, -1.5 to -0.8), -27 (95% CI, 32.3 to -22.6), and -23 (95% CI, -27.8 to -18.3), respectively. All of these measurements favored humeral head stabilization. ConclusionDuring aggressive manual passive stretching in patients with painful stiff shoulders, humeral head stabilization intervention may be more beneficial in improving clinical outcomes such as A-ROM, A-VAS pain levels, and disability scores.

Intelligent Caching for Vehicular Dew Computing in Poor Network Connectivity Environments

In vehicular networks, some edge servers may not function properly due to the time-varying load condition and the uneven computing resource distribution, resulting in a low quality of caching services. To overcome this challenge, we develop a Vehicular dew computing (VDC) architecture for the first time by combining dew computing with vehicular networks, which can achieve wireless communication between vehicles in a resource-constrained environment. Consequently, it is crucial to develop an adaptive caching scheme that empowers vehicles to form efficient cooperation in VDC. In this paper, we propose an intelligent caching scheme based on VDC architecture, which includes two parts. First, to meet the dynamic nature of VDC, a spatiotemporal vehicle clustering algorithm is proposed to establish adaptive cooperation to assist content caching for vehicles. Second, the multi-armed bandit algorithm is employed to select suitable content for caching in vehicles based on real-time file popularity, and a model is established to dynamically update each vehicle’s request preferences. Extensive experiments are conducted to demonstrate that the proposed scheme has excellent performance in terms of cluster head stability and cache hit rate.

Investigating Biomechanical Postural Control Strategies in Healthy Aging Adults and Survivors of Stroke

As the aging populations, both nationwide and worldwide, rapidly increase, falls leading to unintentional injury and death subsequently increase. Thus, developing an understanding of biomechanical postural control strategies used to maintain balance in aging healthy adults, and those that have suffered stroke, are critical. Here, we were interested in how one’s body segments stabilize relative to one another, and in space, in order to maintain balance. To accomplish this goal, we studied 30 healthy individuals and 8 survivors of stroke between 60 and 85 years old, both before and after several weeks of sensory training. Motion capture data were acquired to assess participants’ body kinematics during walking: forward (easiest), forward-tandem, backward, and backward-tandem walking (most challenging). Deviations (via the observation of the absolute angle with deviations, or AADs) of the head, thorax, and lumbar areas relative to an earth vertical reference, as well as how one body segment stabilized in space or relative to the inferior body segment (via the observation of anchoring indices, or AIs), were explored. The results provide metrics (AADs and AIs) that can assess aging posture. Further, the results show an initial indication that, for aging individuals, training could lead to improved head and body stabilization in space.

Partial femoral head replacement: a new innovative hip-preserving approach for treating osteonecrosis of the femoral head and its finite element analysis.

Purpose: Controversy remains regarding the optimal treatment for stage III Osteonecrosis of the femoral head (ONFH). This study presents, for the first time, the precise treatment of stage III ONFH using the "substitute the beam for a pillar" technique and performs a comparative finite element analysis with other hip-preserving procedures. Methods: A formalin-preserved femur of male cadavers was selected to obtain the CT scan data of femur. The proximal femur model was reconstructed and assembled using Mimics 20.0, Geomagic, and UG-NX 12.0 software with four different implant types: simple core decompression, fibula implantation, porous tantalum rod implantation, and partial replacement prosthesis. The finite element simulations were conducted to simulate the normal walking gait, and the stress distribution and displacement data of the femur and the implant model were obtained. Results: The peak von Mises stress of the femoral head and proximal femur in the partial replacement of the femoral head (PRFH) group were 22.8MPa and 37.4MPa, respectively, which were 3.1%-38.6% and 12.8%-37.4% lower than those of the other three surgical methods. Conclusion: The PRFH group exhibits better mechanical performance, reducing stress and displacement in the ONFH area, thus maintaining femoral head stability. Among the four hip-preserving approaches, from a biomechanical perspective, PRFH offers a new option for treating ONFH.

Head stabilization apparatus for high-resolution ophthalmic imaging.

Head movement must be stabilized to enable high-quality data collection from optical instrumentation such as eye trackers and ophthalmic imaging devices. Though critically important for imaging, head stabilization is often an afterthought in the design of advanced ophthalmic imaging systems, and experimental devices often adapt used and/or discarded equipment from clinical devices for this purpose. Alternatively, those seeking the most stable solution possible, including many users of adaptive optics ophthalmoscopy systems, utilize bite bars. Bite bars can provide excellent stability but are time consuming to fabricate, decreasing imaging efficiency, and uncomfortable for many patients, especially the elderly and/or those with prosthodontics such as dentures who may refuse participation in a study that requires one. No commercial vendors specifically offer head mount solutions for experimental ophthalmic imaging devices, resulting in nearly every custom device having a different solution for this commonly encountered problem. Parallelizing the head stabilization apparatus across different custom devices may improve standardization of experimental imaging systems for clinical trials and other multicenter investigations. Here we introduce a head mount design for ophthalmic imaging that is modular, adjustable, and customizable to the constraints of different experimental imaging configurations. The three points of head contact in our solution provide excellent stabilization across a range of head sizes and shapes from small children to adults, and the ease of adjustment afforded by our design minimizes the time to get participants stabilized and comfortable.

Middle trapezius tendon transfer using Achilles allograft for irreparable isolated supraspinatus tendon tears effectively restores the superior stability of the humeral head without restricting range of motion: a biomechanical study

BackgroundMiddle trapezius tendon (MTT) transfer has been suggested for promising treatment of irreparable isolated supraspinatus tendon tears (IISTTs). However, there have been no attempts to assess the biomechanical efficacy of MTT transfer. This study aims to evaluate the biomechanical efficacy of MTT transfer in the setting of IISTTs. MethodsEight fresh-frozen cadaveric shoulders were tested in three conditions (1) intact rotator cuff, (2) IISTTs, and (3) Middle trapezius tendon transfer (MTT) using Achilles allograft for IISTTs. Total humeral rotational range of motion, superior translation of the humeral head, and subacromial contact characteristics were measured at 0°, 20°, and 40° glenohumeral abduction (representing 0°, 30°, and 60° shoulder abduction). Superior translation and subacromial contact pressures were measured at 0°, 30°, 60° and 90° external rotation (ER). Two different MTT muscle loading conditions were investigated. A linear mixed-effects model and Tukey post hoc test were used for statistical analysis. ResultsTotal range of motion was significantly increased after IISTT at 20° abduction (P =.037). There were no changes in total ROM following MTT transfer compared to the IISTT condition (P>.625 for all comparisons). The IISTT condition significantly increased superior translation compared to the intact rotator cuff condition in 0° and 20° abduction with all ER angles (P<.001), 40° abduction/30° ER (P=.016), and 40° abduction/60° ER (P=.002). MTT transfer significantly decreased superior translation of the humeral head at all abduction angles compared to the IISTTs condition (P<.026). MTT transfer significantly decreased peak contact pressure by 638.7 kPa (normal loading) and 726.8 kPa (double loading) at 0° abduction/30° ER compared to the IISTTs condition (P<.001). Mean contact pressure was decreased by 102.8 kPa (normal loading) and 118.0 kPa (double loading) at 0° abduction/30° ER (P<.001) and 101.0 kPa (normal loading) and 99.2 kPa (double loading) at 0° abduction/60° ER (P<.001). MTT transfer at 20° abduction/30° ER with 24N loading significantly decreased contact pressure by 91.2 kPa (P=.035). ConclusionsThe MTT transfer biomechanically restored the superior humeral head translation and reduced the subacromial contact pressure in a cadaveric model of IISTT, while not restricting total ROM. These findings suggest that MTT transfer may have potential as a surgical treatment for IISTTs.

Parameter Identification of KT Equation Based on Flight Test Data of Amphibious Aircraft

To improve the turning efficiency of amphibious aircraft, the flight test of water surface rotation of amphibious aircraft was carried out. Referring to the KT equation of ship maneuverability, the paper established the maneuverability KT equation of the amphibious aircraft on the water surface, and the parameters in the KT equation of amphibious aircraft were identified by forward difference. The test results show that the average value of K value is -0.1095, and the average value of T value is 0.5490. The turning efficiency of amphibious aircraft is low, the maneuverability is insufficient, and the heading stability is good. At the same time, the steering response is fast and the delay is low.

Risk of injury and kinematic assessment of the shoulder biomechanics during strokes in padel players: a cross-sectional study.

Padel players commonly suffer from shoulder pain and the particularly high incidence is probably linked to the high frequency of strokes. In addition, due to the repetitive technical gesture, an adequate technique is essential in terms of performance and injury risk prevention. Aim of this study was to objectively evaluate shoulder kinematic during the athletic gesture to analyze the risk factors linked to padel strokes. Professional and amateur padel players underwent a three-dimensional motion analysis of the padel strokes utilizing optoelectronic and surface electromyography systems (BTS Bioengineering, Garbagnate Milanese, Milan, Italy). Twelve padel players were included in this study (10 professional players in Group A and 10 amateurs in Group B). Experience influences the execution of padel strokes with a significant difference between group A and B in terms of gleno-humeral rotation and scapular tilt. Moreover, a subgroup analysis revealed that male players execute voleè with a higher external rotation (P=0.043), and forehand with a higher scapular tilt (P=0.044). The results confirm that the high ranges of motion of the overhead strokes could rise the risk of slap lesion, impingement, and glenohumeral internal rotation deficit. However, a correct execution of the athletic gesture is linked with a dynamic stabilization of the humeral head. In conclusion, the kinematic analysis could help in the early identification of the kinematic alteration to build a tailored rehabilitation plan based on the athlete's needs.