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.

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.

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.

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.

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.

Structured Estimation of Tire Forces and the Ground Slope Using SM Observers

In agricultural context, the principal cause of serious accidents for all-terrain vehicles(ATVs) is rollover. The most important parameters related to this risk is the ground slope. In this paper, we propose a structured observer to estimate the system states and the longitudinal tire forces using only wheel angular velocities measurement. The robust estimation is based on a second order sliding mode observer. This estimation is then used to build up a ground slope estimation. The algorithm is composed by two cascaded estimators. This structured estimation is then applied to the model of an agricultural vehicle G7(GregoireTM) integrated in the driving simulation environment SCANeRTM-Studio.

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.

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.

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.