Analysis of Biomechanical Characteristics of Football Players at Different Levels Kicking with the Inner Edge of Instep

This study aims to analyze the difference in biomechanical properties of football players at different levels when kicking the football with the inner edge of the instep. Before the experiment, ten football players were selected; five were higher than the national level (group A), and the other five players were lower than the national level II (group B). During the experiment, the motion process was captured by a high-speed camera for biomechanical analysis. It was found that in group A, the thigh and leg swung in less time and larger amplitude, the acceleration of backswing and forward swing of the leg was larger, and the angular velocity of forward swing was also larger. At the moment of touching the ball, in the sagittal plane, the ankle joint angle and angular velocity of group A were larger than those of group B (P < 0.05). In conclusion, the high-level athletes can complete the high-quality kicking through a larger swing amplitude and speed of the kicking leg. In the training process, the athletes should pay attention to the speed and strength of the kicking leg to improve the kicking level.     

Hydrodynamic calculations on the movements of cilia and flagella I. Paramecium

Calculations of the velocity profile, force, moment and bending moment using a theoretical model are carried out for the three-dimensional “conical-helical” beat of a cilium of Paramecium multimicro-nucleatum. The mean velocity profile obtained by numerical computation is found to be twisted in form: it is inclined at a slight angle to the effective stroke at the top of the cilia sublayer, but twists around with the recovery stroke in the lower part of the sublayer. The force and moment are larger during the fast effective stroke, but over a complete cycle their contributions are approximately zero. Calculations on the bending moments reveals that they are larger during the recovery stage of the beating cycle.     

A novel application of velocity-based force control for use in robotic biomechanical testing

This paper presents a novel application of a velocity-based force control routine used for robotic biomechanical testing. The routine employs a jog function, available from the robot's motion commands, that permits easy adjustment of velocity on each axis. Force and moment targets are achieved by adjusting jog velocities in proportion to force or moment errors while limiting the maximum velocity of the system. The force control jog routine does not require specimen stiffness values and is inherently stable. The performance of the method was shown to be suitable for unconstrained in vitro spine testing in a rabbit model where extremely small motions are necessary to maintain the target force values. The jogging feature on which this work is based is a feature available on most robots and is equally applicable to a serial robot. The simplicity, stability, and performance of this method warrant its consideration for other robotic biomechanical testing applications where force control is required.     

The biomechanics of skipping gaits: a third locomotion paradigm?

Skipping, a gait children display when they are about four- to five-years-old, is revealed to be more than a behavioural peculiarity. By means of metabolic and biomechanical measurements at several speeds, the relevance of skipping is shown to extend from links between bipedal and quadrupedal locomotion (namely galloping) to understanding why it could be a gait of choice in low-gravity conditions, and to some aspects of locomotion evolution (ground reaction forces of skipping seem to originate from pushing the walking gait to unnaturally high speeds). When the time-courses of mechanical energy and the horizontal ground reaction force are considered, a different locomotion paradigm emerges, enabling us to separate, among the bouncing gaits, the trot from the gallop (quadrupeds) and running from skipping (bipeds). The simultaneous use of pendulum-like and elastic mechanisms in skipping gaits, as shown by the energy curve analysis, helps us to understand the low cost of transport of galloping quadrupeds.     

Effects of velocity and weight support on ground reaction forces and metabolic power during running

The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.     

Ground reaction forces during the power clean

Identifying and understanding the key biomechanical factors that exemplify the power clean can provide athletes the proper tools needed to prevail at a competitive event. Therefore, the purpose of this study was to characterize and describe ground reaction forces (Fz) during the power clean lift. Three 60-Hz motion-detecting cameras and an AMTI force plate were used to collect data from 10 collegiate weightlifting men who performed a power clean at 60 and 70% of their last competitive maximum clean. The results revealed that a greater peak force (Fz) was produced during the second pull compared with the first pull and unweighted phases in both percentage lifts. As the system weight increased from 60 to 70%, the peak force (Fz) increased for the first pull and unweighted phases and decreased during the second pull phase. Learning the proper technique of the power clean may provide athletes the basic understanding needed to be competitive in a weightlifting or sporting event.     

Performance of noncountermovement jump with both knee and hip joints fully extended

The relationships between neuromuscular performance and biomechanical variables were studied in maximum vertical jumps to examine the factors influencing the performance of a noncountermovement jump. Keeping their knee and hip joint fully extended, five healthy subjects performed four kinds of noncountermovement jumps and one countermovement jump, during which ankle joint angle, platform force, and surface electromyograms of a triceps surae muscle were recorded. In the four noncountermovement jumps, the magnitude of activation and force at the onset of a shortening contraction of the triceps surae muscle were controlled at four different levels. Performance parameters of the noncountermovement jumps, maximum angular velocity of the ankle angle and flight time, correlated with the platform force at the onset of the plantar flexion. Furthermore the integrated electromyograms of the triceps surae muscle before the plantar flexion were correlated with the maximum angular velocity of the ankle angle and the force at the plantar flexion onset. The findings suggest that the efficient utilization of the muscle characteristic contributes to an enhancement of the noncountermovement jump.     

Effects of a knee extension constraint brace on selected lower extremity motion patterns during a stop-jump task

Small knee flexion angle during landing has been proposed as a potential risk factor for sustaining noncontact ACL injury. A brace that promotes increased knee flexion and decreased posterior ground reaction force during landing may prove to be advantageous for developing prevention strategies. Forty male and forty female recreational athletes were recruited. Three-dimensional videographic and ground reaction force data in a stop-jump task were collected in three conditions. Knee flexion angle at peak posterior ground reaction force, peak posterior ground reaction force, the horizontal velocity of approach run, the vertical velocity at takeoff, and the knee flexion angle at takeoff were compared among conditions: knee extension constraint brace, nonconstraint brace, and no brace. The knee extension constraint brace significantly increased knee flexion angle at peak posterior ground reaction force. Both knee extension constraint brace and nonconstraint brace significantly decreased peak posterior ground reaction force during landing. The brace and knee extension constraint did not significantly affect the horizontal velocity of approach run, the vertical velocity at takeoff, and the knee flexion angle at takeoff. A knee extension constraint brace exhibits the ability to modify the knee flexion angle at peak posterior ground reaction force and peak posterior ground reaction force during landing.     

Differentiation of ankle sprain motion and common sporting motion by ankle inversion velocity

This study investigated the ankle inversion and inversion velocity between various common motions in sports and simulated sprain motion, in order to provide a threshold for ankle sprain risk identification. The experiment was composed of two parts: Firstly, ten male subjects wore a pair of sport shoes and performed ten trials of running, cutting, jump-landing and stepping-down motions. Secondly, five subjects performed five trials of simulated sprain motion by a supination sprain simulator. The motions were analyzed by an eight-camera motion capture system at 120 Hz. A force plate was employed to record the vertical ground reaction force and locate the foot strike time for common sporting motions. Ankle inversion and inversion velocity were calculated by a standard lower extremity biomechanics calculation procedure. Profiles of vertical ground reaction force, ankle inversion angle and ankle inversion velocity were obtained. Results suggested that the ankle was kept in an everted position during the stance. The maximum ankle inversion velocity ranged from 22.5 to 85.1°/s and 114.0 to 202.5°/s for the four tested motions and simulated sprain motion respectively. Together with the ankle inversion velocity reported in the injury case (623°/s), a threshold of ankle inversion velocity of 300°/s was suggested for the identification of ankle sprain. The information obtained in this study can serve as a basis for the development of an active protection apparatus for reducing ankle sprain injury.     

Influence of material properties on the mechanical behaviour of the L5-S1 intervertebral disc in compression: a nonlinear finite element study

A simple finite element model of the L₅-S₁ intervertebral disc body has been constructed; it is circular and symmetrical about the sagittal plane. The annulus fibrosus of the model was idealized as an inhomogeneous composite of an isotropic ground substance, reinforced by helically oriented collagen fibres so that the model has six different structural components namely: cortical bone, cancellous bone, cartilaginous endplates, nucleus pulposus, ground substance and collagen fibres. A sensitivity analysis of the material properties of each structural component was carried out by varying those properties for one structural component at a time and evaluating the changes in the biomechanical response to compressive displacements. Experimentally available relations between the applied compressive force and the vertical displacements, the nucleus pulposus pressure increase and the disc lateral bulge were used to evaluate the biomechanical responses for each set of material properties. Results showed that both the Poisson's ratio and the Young's modulus of the ground substance play an important role in the prediction of the biomechanical response.     

Estimation of low back loading on nurses during patient handling tasks: the importance of bedside reaction force measurement

By means of video recording, measurement of ground reaction forces, and biomechanical modeling of the lower part of the body, the low back loading of nurses during patient handling can be estimated. In this study the force exerted on the bedside by a nurse during different patient handling tasks was measured, and the contribution to the moment at the L4/L5 joint was investigated. It is shown that the bedside reaction moment contributes significantly to the total moment, and could lead to substantial over-estimation if not appropriately included in the calculations, when using an upward biomechanical model for estimating the spinal load of nurses during patient handling tasks.     

Changes in landing biomechanics during a fatiguing landing activity.

The objective of this study was to investigate the effects of LE fatigue on ground impact force, LE kinematics, and LE kinetics during landing. Ground reaction force (GRF), kinematic, and electromyogram (EMG) data were collected from 12 male subjects during a fatiguing landing activity (FLA). This activity allowed not only the biomechanical differences between unfatigued and fatigued landings to be determined, but also the time history of multiple biomechanical variables as fatigue progressed. EMG mean frequency analysis using data collected immediately before and after the FLA indicated that subjects experienced fatigue of the quadriceps muscles. Results indicated a decrease in ground impact force and an increase in maximum joint flexion during landing with fatigue. Joint impulse values were consistent with a distal to proximal redistribution of extensor moment production. Potential reasons for this redistribution are discussed. A trend reversal in hip and ankle impulse during the activity suggest a change in landing strategy as fatigue progressed. The data also suggest that the measured changes in landing biomechanics may have been influenced by other factors, in addition to fatigue, such as a neuromuscular protective mechanism to decrease impact force magnitude.     

Effects of Forefoot Shoe on Knee and Ankle Loading during Running in Male Recreational Runners

Objectives: Although overuse running injury risks for the ankle and knee are high, the effect of different shoe designs on Achilles tendon force (ATF) and Patellofemoral joint contact force (PTF) loading rates are unclear. Therefore, the primary objective of this study was to compare the ATF at the ankle and the PTF and Patellofemoral joint stress force (PP) at the knee using different running shoe designs (forefoot shoes vs. normal shoes). Methods: Fourteen healthy recreational male runners were recruited to run over a force plate under two shoe conditions (forefoot shoes vs. normal shoes). Sagittal plane ankle and knee kinematics and ground reaction forces were simultaneously recorded. Ankle joint mechanics (ankle joint angle, velocity, moment and power) and the ATF were calculated. Knee joint mechanics (knee joint angle velocity, moment and power) and the PTF and PP were also calculated. Results: No significant differences were observed in the PTF, ankle plantarflexion angle, ankle dorsiflexion power, peak vertical active force, contact time and PTF between the two shoe conditions. Compared to wearing normal shoes, wearing the forefoot shoes demonstrated that the ankle dorsiflexion angle, knee flexion velocity, ankle dorsiflexion moment extension, knee extension moment, knee extension power, knee flexion power and the peak patellofemoral contact stress were significantly reduced. However, the ankle dorsiflexion velocity, ankle plantarflexion velocity, ankle plantarflexion moment and Achilles tendons force increased significantly. Conclusions: These findings suggest that wearing forefoot shoes significantly decreases the patellofemoral joint stress by reducing the moment of knee extension, however the shoes increased the ankle plantarflexion moment and ATF force. The forefoot shoes effectively reduced the load on the patellofemoral joint during the stance phase of running. However, it is not recommended for new and novice runners and patients with Achilles tendon injuries to wear forefoot shoes.     

Modelling, simulation and optimisation of a human vertical jump.

This paper describes an efficient biomechanical model of the human lower limb with the aim of simulating a real human jump movement consisting of an upword propulsion, a flying and a landing phase. A multiphase optimal control technique is used to solve the muscle force sharing problem. To understand how intermuscular control coordinates limb muscle excitations, the human body is reduced to a single lower limb consisting of three rigid bodies. The biomechanical system is activated by nine muscle-tendon actuators representing the basic properties of muscles during force generation. For the calculation of the minimal muscle excitations of the jump movement, the trajectory of the hip joint is given as a rheonomic constraint and the contact forces (ground reaction forces) are determined by force plates. Based on the designed musculoskeletal model and on the differential equations of the multibody system, muscle excitations and muscle forces necessary for a vertical jump movement are calculated. The validity of the system is assessed comparing the calculated muscle excitations with the registered surface electromyogramm (EMG) of the muscles. The achieved results indicate a close relationship between the predicted and the measured parameters.     

Prediction of the loading along the leg during snow skiing.

The complete force and moment of each cross section of the leg between the ski boot top and the knee during normal skiing were predicted from measurements of the force and moment under the toe and heel of the boot and the flexion of the ankle. The force and moment components predicted at the base of the boot were significantly different from those predicted at sites of potential injury at the boot top and the knee. The maximum torsional and maximum varus-valgus moments predicted at the knee over all subjects tested were 70 Nm and 149 Nm, which are within the estimated range of the ultimate strength of the knee without support from contracted muscles crossing the knee. Regression analyses were used to find the force components at the base of the boot that best predict the bending and torsional moments at the boot top and knee. The torsional moments at the boot top and knee are best predicted by the medial-lateral force at the toe. The varus-valgus moment at the boot top and knee are best predicted by the resultant medial-lateral force component at the base of the boot. The set of best predictors of the anterior-posterior bending moments at the boot top and knee includes the vertical force at the toe, the vertical force at the heel and the component of the total vertical force directed perpendicular to the leg.     

How do low horizontal forces produce disproportionately high torques in human locomotion?

Although horizontal ground forces are only approximately 15% of vertical forces, they account for 47% and 33% of the metabolic cost in walking and running. To explain these disproportionately high metabolic costs, we hypothesized that low horizontal ground forces generate relatively high torques on body segments during locomotion and this is mediated by long moment arms. We compared external force moment arms and discreet torques applied to the body segments by horizontal and vertical forces during walking and running. Sixteen subjects (21.9+/-1.9 years) walked at 1.5m/s and ten subjects (23.2+/-2.0 years) ran at 3.83 m/s. Segmental torques in the sagittal plane were partitioned into components due to horizontal and vertical forces and quantified by their angular impulses. The mean (+/-S.E.) ratios of horizontal to vertical ground forces (GF ratio) and angular impulses (AI ratio) in walking were 0.131 (+/-0.003, 95% confidence interval (CI) 0.124-0.137) and 0.530 (+/-0.018, CI 0.497-0.569). Results were similar in running. In both gaits the AI ratios were significantly greater than the GF ratios because the respective CI's did not overlap. The horizontal forces produced 53% and 41% as much angular impulse on the body segments, as did the vertical forces in walking and running despite being only 13% as large. In the two movements the moment arms for the horizontal forces averaged across foot, leg, thigh, and trunk body segments were 3.8 fold larger than those for the vertical forces. The data supported the hypothesis and suggest that the relatively low horizontal vs. vertical forces accounted for a disproportionately higher percentage of the angular impulses placed on the body segments and this effect was due to relatively long moment arms for horizontal forces. These results partially explain the relatively large metabolic cost of generating relatively low horizontal forces.     

The vertical leap ofCercopithecus aethiops sabaeus: Biomechanics and anatomy

In this study, one positional mode, the vertical leap, is selected from the larger repertoire of habitual behaviors of whichCercopithecus aethiops sabaeus is capable, and is quantitatively analyzed. A cinematographic biomechanical analysis of the vertical leap provides a view of the kinematics (time-space properties of the leap) as well as the kinetics (or force properties) of the leap. These are then discussed with regard to anatomical potential. The analysis elucidates three distinct phases of motion during which the moving body segments linked via their connecting joints, affect one another in the production of the leap. The total positional adaptation ofC. a. sabaeus may only be determined after similar analyses are performed for all postural and locomotor modes. The present detailed analysis of vertical leaping is intended to present data for this one positional mode found to be of primary importance in the arboreal environment and in moving from the ground into the trees. In addition a methodology is illustrated for application in similar primate positional studies. A version of this paper was presented at the 43rd Annual Meeting of the American Association of Physical Anthropologists (March, 1974). This research was partially supported by Sigma Xi Grant-in-Aid of Research, Behavioral Science Foundation Fellowship.     

Longer moment arm results in smaller joint moment development, power and work outputs in fast motions

Effects of moment arm length on kinetic outputs of a musculoskeletal system (muscle force development, joint moment development, joint power output and joint work output) were evaluated using computer simulation. A skeletal system of the human ankle joint was constructed: a lower leg segment and a foot segment were connected with a hinge joint. A Hill-type model of the musculus soleus (m. soleus), consisting of a contractile element and a series elastic element, was attached to the skeletal system. The model of the m. soleus was maximally activated, while the ankle joint was plantarflexed/dorsiflexed at a variation of constant angular velocities, simulating isokinetic exercises on a muscle testing machine. Profiles of the kinetic outputs (muscle force development, joint moment development, joint power output and joint work output) were obtained. Thereafter, the location of the insertion of the m. soleus was shifted toward the dorsal/ventral direction by 1cm, which had an effect of lengthening/shortening the moment arm length, respectively. The kinetic outputs of the musculoskeletal system during the simulated isokinetic exercises were evaluated with these longer/shorter moment arm lengths. It was found that longer moment arm resulted in smaller joint moment development, smaller joint power output and smaller joint work output in the larger plantarflexion angular velocity region (>120 degrees/s). This is because larger muscle shortening velocity was required with longer moment arm to achieve a certain joint angular velocity. Larger muscle shortening velocity resulted in smaller muscle force development because of the force-velocity relation of the muscle. It was suggested that this phenomenon should be taken into consideration when investigating the joint moment-joint angle and/or joint moment-joint angular velocity characteristics of experimental data.     

Segment-interaction analysis of the stance limb in sprint running

A high angular velocity of the thigh of the stance limb, generated by hip extensor musculature, is commonly thought to be a performance-determining factor in sprint running. However, the thigh segment is a component of a linked system (i.e., the lower limb), therefore, it is unlikely that the kinematics of the thigh will be due exclusively to the resultant joint moment (RJM) at the hip. The purpose of this study was to quantify, by means of segment-interaction analysis, the determinants of sagittal plane kinematics of the lower limb segments during the stance phase of sprint running. Video and ground reaction force data were collected from four male athletes performing maximal-effort sprints. The analysis revealed that during the first-third of the stance phase, a hip extension moment was the major determinant of the increasing angular velocity of the thigh. However, during the mid-third of stance, hip and knee extension moments and segment interaction effects all contributed to the thigh attaining its peak angular velocity. Extension moments at the ankle, and to a lesser extent the knee, were attributed with preventing the 'collapse' of the shank under the effects of the interactive moment due to ground reaction force. The angular acceleration of the foot was determined almost completely by the RJM at the ankle and the interactive moment due to ground reaction force. Further research is required to determine if similar results exit for a wide range of athletes and for other stages of a sprint race (e.g. early acceleration, maximal velocity, and deceleration phases).     

Handling of impact forces in inverse dynamics

In the standard inverse dynamic method, joint moments are assessed from ground reaction force data and position data, where segmental accelerations are calculated by numerical differentiation of position data after low-pass filtering. This method falls short in analyzing the impact phase, e.g. landing after a jump, by underestimating the contribution of the segmental accelerations to the joint moment assessment. This study tried to improve the inverse dynamics method for the assessment of knee moment by evaluating different cutoff frequencies in low-pass filtering of position data on the calculation of knee moment. Next to this, the effect of an inclusion of direct measurement of segmental acceleration using accelerometers to the inverse dynamics was evaluated. Evidence was obtained that during impact, the contribution of the ground reaction force to the sagittal knee moment was neutralized by the moments generated by very high segmental accelerations. Because the accelerometer-based method did not result in the expected improvement of the knee moment assessment during activities with high impacts, it is proposed to filter the ground reaction force with the same cutoff frequency as the calculated accelerations. When this precaution is not taken, the impact peaks in the moments can be considered as artifacts. On the basis of these findings, we recommend in the search to biomechanical explanations of chronic overuse injuries, like jumper's knee, not to consider the relation with impact peak force and impact peak moment.