The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes

Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.

Reduction in ground reaction force variables with instructed barefoot running

Backgound:Barefoot(BF) running has recently increased in popularity with claims that it is more natural and may result in fewer injuries due to a reduction in impact loading.However,novice BF runners do not necessarily immediately switch to a forefoot strike pattern.This may increase mechanical parameters such as loading rate,which has heen associated with certain running-related injuries,specifically,tibial stress fractures.patellofemoral pain,and plantar iasciitis.The purpose of this study was to examine changes in loading parameters between typical shod running and instructed BF running with real-time force feedback.Methods:Forty-nine patients seeking treatment for a lower extremity injury ran on a force-sensing treadmill in their typical shod condition and then BF at the same speed.While BF they received verbal instruction and real-time feedback of vertical ground reaction forces.Results:While 92%of subjects(n = 45) demonstrated a rearfoot strike pattern when shod,only 2%(n = 1) did during the instructed BF run.Additionally,while BF 47%(n = 23) eliminated the vertical impact transient in all eight steps analyzed.All loading variables of interest were significantly reduced from the shod to instructed BF condition.These included maximum instantaneous and average vertical loading rates of the ground reaction force(p 【 0.0001),stiffness during initial loading(p 【 0.0001).and peak medial(p = 0.001) and lateral(p 【 0.0001) ground reaction forces and impulses in the vertical(p 【 0.0001).medial(p = 0.047),and lateral(p 【 0.0001) directions.Conclusion:As impact loading has been associated with certain running-related injuries,instruction and feedback on the proper forefoot strike pattern may help reduce the injury risk associated with transitioning to BF running.

Analysis of kinematic data and determination of ground reaction force of foot in slow squat

In the present paper, the ground reaction force （GRF） acting on foot in slow squat was determined through a force measuring system, and at the same time, the kinematic data of human squat were obtained by analyzing the photographed image sequences. According to the height and body weight, six healthy volunteers were selected, three men in one group and the other three women in another group, and the fundamental parameters of subjects were recorded, including body weight, height and age, etc. Based on the anatomy characteristics, some markers were placed on the right side of joints. While the subject squatted at slow speed on the force platform, the ground reaction forces on the forefoot and heel for each foot were obtained through calibrated force platform. The analysis results show that the reaction force on heel is greater than that on forefoot, and double feet have nearly constant force. Moreover, from processing and analyzing the synchronously photographed image sequences in squat, the kinematic data of human squat were acquired, including mainly the curves of angle, angular velocity and angular acceleration varied with time for knee, hip and ankle joints in a sagittal plane. The obtained results can offer instructive reference for photographing and analyzing the movements of human bodies, diagnosing some diseases, and establishing in the future appropriate mathematical models for the human motion.

One hundred marathons in 100 days:Unique biomechanical signature and the evolution of force characteristics and bone density

Background:An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance.An extraordinary runner(age=55 years,height=1.81 m,mass=92 kg) scheduled a marathon a day for 100 consecutive days.His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.Methods:Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion.The case’s running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.Results:The case’s peak vertical loading rate(Δx=-61.9 body weight(BW)/s or-57%),peak vertical ground reaction force(Δx=-0.38 BW or-15%),and peak braking force(Δx=-0.118 BW or-31%) were remarkably lower(p<0.05) than the control group at~3.3 m/s.The relatively low loading-related magnitudes were attributed to a remarkably high duty factor(0.41) at the evaluated speed.The foot strike angle of the marathoner(29.5°) was greater than that of the control group,affecting the peak vertical loading rate.Muscle powers in the lower extremity were also remarkably low in the case vs.controls:peak power of knee absorption(Δx=-9.16 watt/kg or-48%) and ankle generation(Δx=-3.17 watt/kg or-30%).The bone mineral density increased to 1.245 g/cm;(+2.98%) near completion of the challenge,whereas the force characteristics showed no statistically significant change.Conclusion:The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

The Human Ankle-Foot Complex as a Multi-Configurable Mechanism during the Stance Phase of Walking

The objective of this study is to investigate the biomechanical functions of the human ankle-toot complex during the stancephase of walking. The three-dimensional (3D) gait measurement was conducted by using a 3D infrared multi-camera system anda force plate array to record the Ground Reaction Forces (GRF) and segmental motions simultaneously. The ankle-foot complexwas modelled as a four-segment system, connected by three joints: talocrural joint, sub-talar joint and metatarsophalangeal joint.The subject-specific joint orientations and locations were determined using a functional joint method based on the particleswarm optimisation algorithm. The GRF moment arms and joint moments acting around the talocrural and sub-talar joints werecalculated over the entire stance phase. The estimated talocrural and sub-talar joint locations show noticeable obliquity. Thekinematic and kinetic results strongly suggest that the human ankle-foot complex works as a mechanical mechanism with twodifferent configurations in stance phase of walking. These lead to a significant decrease in the GRF moment arms therebyincreasing the effective mechanical advantages of the ankle plantarflexor muscles. This reconfigurable mechanism enhancesmuscle effectiveness during locomotion by modulating the gear ratio of the ankle plantarflexor muscles in stance. This studyalso reveals many factors may contribute to the locomotor function of the human ankle-foot complex, which include not only itsre-configurable structure, but also its obliquely arranged joints, the characteristic heel-to-toe Centre of Pressure (COP) motionand also the medially acting GRF pattern. Although the human ankle-foot structure is immensely complex, it seems that itsconfiguration and each constitutive component are well tuned to maximise locomotor efficiency and also to minimise risk ofinjury. This result would advance our understanding of the locomotor function of the ankle-foot complex, and also the intrinsicdesign of the ankle-foot musculoskeletal structure. Moreover, this may also provide implications for the design of bionicprosthetic devices and the development of humanoid robots.

Is changing footstrike pattern beneficial to runners?

Some researchers, running instructors, and coaches have suggested that the "optimal" footstrike pattern to improve performance and reduce running injuries is to land using a mid-or forefoot strike. Thus, it has been recommended that runners who use a rearfoot strike would benefit by changing their footstrike although there is little scientific evidence for suggesting such a change. The rearfoot strike is clearly more prevalent. The major reasons often given for changing to a mid-or forefoot strike are(1) it is more economical;(2) there is a reduction in the impact peak and loading rate of the vertical component of the ground reaction force; and(3) there is a reduction in the risk of a running-related injuries. In this paper,we critique these 3 suggestions and provide alternate explanations that may provide contradictory evidence for altering one's footstrike pattern.We have concluded, based on examining the research literature, that changing to a mid-or forefoot strike does not improve running economy, does not eliminate an impact at the foot-ground contact, and does not reduce the risk of running-related injuries.

Coordinated control strategy for robotic-assisted gait training with partial body weight support

Walking is the most basic and essential part of the activities of daily living. To enable the elderly and non-ambulatory gait-impaired patients, the repetitive practice of this task, a novel gait training robot(GTR) was designed followed the end-effector principle, and an active partial body weight support(PBWS) system was introduced to facilitate successful gait training. For successful establishment of a walking gait on the GTR with PBWS, the motion laws of the GTR were planned to enable the phase distribution relationships of the cycle step, and the center of gravity(COG) trajectory of the human body during gait training on the GTR was measured. A coordinated control strategy was proposed based on the impedance control principle. A robotic prototype was developed as a platform for evaluating the design concepts and control strategies. Preliminary gait training with a healthy subject was implemented by the robotic-assisted gait training system and the experimental results are encouraging.

Early Identification and Visualization of Parkinsonian Gaits and their Stages Using Convolution Neural Networks and Finite Element Techniques

Parkinson’s Disease(PD)is a neurodegenerative disease which shows a deficiency in dopaminehormone in the brain.It is a common irreversible impairment among elderly people.Identifying this disease in its preliminary stage is important to improve the efficacy of the treatment process.Disordered gait is one of the key indications of early symptoms of PD.Therefore,the present paper introduces a novel approach to identify pa rkinsonian gait using raw vertical spatiotemporal ground reaction force.A convolution neural network(CNN)is implemented to identify the features in the parkinsonian gaits and their progressive stages.Moreover,the var iations of the gait pressures were visually recreated using ANSYS finite element software package.The CNN model has shown a 97%accuracy of recognizing parkinsonian gait and their different stages,and ANSYS model is implemented to visualize the pressure variation of the foot during a bottom-up approach.

An efficient tool for Parkinson's disease detection and severity grading based on time-frequency and fuzzy features of cumulative gait signals through improved LSTM networks

Parkinson's disease(PD)is a widespread neurodegenerative condition that affects many individuals annually.Early identification and monitoring of disease progression are crucial to effectively managing symptoms and preventing motor complications.This research proposes an automated PD diagnosis and severity-grading model based on time-frequency and fuzzy features using improved uni-directional and bi-directional long short-term memory networks with sensitive hyperparameters optimization.We utilize vertical ground reaction force signals collected from Physionet's publicly available dataset recorded during regular and dual-task clinical trials of walking measurements.Only the cumulative signal of both feet was then utilized and segmented into 30-s windows without further pre-processing.Subsequently,we extracted only four key time-frequency and fuzzy features from each segment,effectively capturing the signal's inherent uncertainty.Bayesian optimization is employed in both detection and grading approaches to fine-tune the two critical hyperparameters:the initial learning rate and the number of hidden units in the network.The detection phase yields an exceptional accuracy of 99.19%,surpassing state-of-the-art studies with the same dataset.In the grading phase,classification based on the unified PD rating scale values achieves an accuracy of 92.28%.The proposed study delves into the potential of cumulative gait signals as a powerful diagnostic tool for PD,aiming to extract precise and intricate information by implementing straightforward and minimal processing endeavors.This method demonstrates significant effi-ciency in terms of complexity,cost,and energy consumption by utilizing a single-dimensional signal,eliminating the need for pre-processing steps,and limiting the features used for training.

A stability locomotion-control strategy for quadruped robots with center-of-mass dynamic planning

Locomotion stability is essential for controlling quadruped robots and adapting them to unstructured terrain.We propose a control strategy with center-of-mass(CoM)dynamic planning for the stable locomotion of these robots.The motion trajectories of the swing legs are synchronized with the CoM of the robot.To implement the synchronous control scheme,we adjusted the swing legs to form a support triangle.The strategy is applicable to both static walk gait and dynamic trot gait.In the motion control processes of the robot legs,the distribution of the ground reaction forces is optimized to minimize joint torque and locomotion energy consumption.We also used an improved joint-torque controller with varied controller coefficients in the stance and swing phases.The simulation and experimental results demonstrate that the robot can complete omnidirectional locomotion in both walk and trot gaits.At a given locomotion speed,the stability margins for the robot during walking and trotting were 27.25%and 37.25%higher,respectively,than in the scheme without CoM planning.The control strategy with energy consumption optimization(ECO)reduced the energy consumption of the robot in walk and trot gaits by 11.25%and 13.83%,respectively,from those of the control scheme without ECO.

A Kinetic Analysis of Golf Swings Performed by Healthy Older Adult Males

Purpose The kinetic profile of golf swings is frequently assessed in biomechanics.However,most research is limited to young golfers,so the mechanical demands on older athletes are poorly documented.This study provides kinetic data of older golfers swinging with a driver and a 6-iron.Methods We examined 17 older,skilled male golfers(62.2±8.8 years,handicap 8.7±4.9)using a 10-camera motion cap-ture system and two force platforms.Three-dimensional net support moments,joint moments of the hip,knee,and ankle,ground reaction forces(GRF),and the inclination angles between the centre of mass(COM)and centre of pressure(COP)were calculated and tested for between-club differences.Results The 3D net support moments of the trail leg were higher when using the driver,while those of the lead leg were higher with the 6-iron.Between-club differences existed in the relative contribution from each joint,the COM-COP inclina-tion angles,and the peak GRF.Conclusion The mechanical demands of golf swings on older adults differ between a driver and a 6-iron,which likely affects the balance and control strategies required.This improved understanding of the kinetic profiles of golf swings in older adults provide clinicians and coaches better means to maintain older golfers active and healthy for longer.

Effects of Eccentric Pre-loading on Concentric Vertical Jump Performance in Young Female Athletes

Purpose This study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes.Methods Twenty young female athletes ranging from 9 to 17 years old performed the following vertical jumps in random order:static jumps(SJs),counter-movement jumps(CMJs),and drop jumps(DJs)from drop heights of 20,30,and 40 cm(DJ20,DJ30,and DJ40,respectively).Measurements included peak force(PF),peak rate of force development(RFD),peak power(PP),eccentric impulse(ECC),and concentric impulse(CON).Measurements of growth included age,maturity offset,height,body mass,fat-free mass,and thigh muscle cross-sectional area(CSA).Results PF increased from the SJ-DJ20(P<0.009),then plateaued from DJ20-DJ40(P=1.000).RFD remained the same from SJ-CMJ(P=1.000),increased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=0.874).PP increased from the SJ-CMJ(P<0.001),then plateaued from the CMJ-DJ40(P≥0.486).CON remained the same across all verti-cal jumps(P=1.000),while ECC increased from the SJ-DJ40(P≤0.038).Jump height(JH)increased from the SJ-CMJ(P<0.001),decreased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=1.000).The change in PP from the SJ-CMJ(ΔCMJ-SJ)was related to all measurements of growth except CSA(r=0.558-0.815).Conclusion Young females produced greater power during the CMJ than SJ,but equivalent power from the CMJ-DJ40,despite increases in ECC.Additionally,ΔCMJ-SJ was not related to CSA,which suggests other underlying mechanisms affect stretch-shortening cycle utilization in young female athletes.