Component Of Reaction Force Research Articles

Differences in the structure of variability in ground reaction force trajectories provide additional information about variability in the golf swing

The study presents a novel application of measures of the structure of variability to ground reaction force trajectories and highlights the use of such measures to provide valuable information about coordination of the golf swing. The variability and regularity of ground reaction force trajectories were quantified for iron and driver shots from three participants with different skill levels. Pointwise median absolute deviation was used to indicate the variability of ground reaction force trajectories across their length, and two alternative methodologies, sample entropy and cross-sample entropy, were used to determine their regularity. For both driver and iron shots, results showed that while there was no difference in the magnitude of variability between any of the participants, there were differences in the structure of this variability. In general, the ground reaction force of the highest skilled participant was significantly more regular than that of the lesser skilled golfers. However, differences occurred across the various components of ground reaction force. Thus, entropy measures can provide additional valuable information concerning dissimilarities among golfers of various skill levels and may indicate differences in neuromuscular system coordination during the golf swing. This study highlights the importance of considering the structure of variability, as well as its magnitude, and describes methods which could be applied to further investigations.

Impact Control in High-Intensity Interval Training Can Be Improved by Creatine Supplementation

High-intensity interval training (HIIT) is an exercise mode designed to repeatedly stress the body with intense stimulus. Intense running can increase impact forces and alter muscle activation intensity. As skeletal muscles have an important role in shock attenuation, the depletion of muscle phosphorylcreatine (PCr) stores and the diminished energy sources could lead to exhaustion and impairments in the protective functions of muscle during running. We hypothesize creatine supplementation could avoid peripheral fatigue during intense exercise and reduce impairments on shock attenuation. PURPOSE: This study investigated the effects of creatine supplementation on biomechanical parameters related to shock attenuation during a session of HIIT. METHODS: A single-blind, placebo-controlled, crossover design was adopted to test 8 elite soccer players (males; 16.3± 0.5 years; 70.7 ± 4.16 kg; 1.78± 0.06 m) during HITT sessions under two conditions: after placebo supplementation (Pl) and after creatine supplementation (Cr). HITT test sessions consisted of an intermittent test (5 bouts of running) with constant load applied until exhaustion was reached. The vertical component of Ground Reaction Force (VGRF) and Electromyography (EMG) data were recorded by Gaitway and Lynx-EMG Systems, respectively. Heart rate (HR), Rated Perceived Exertion (RPE – Borg’s Scale) and lactate concentration were also obtained. RESULTS: Creatine supplementation did not affect HR, RPE and lactate concentration. Decreased values (p<0.05) of magnitude of first peak (Fy1) of VGRF and impulse of first 50 ms (Imp50) were observed for Cr (about 16.2 – 24.2% and 34.3% of decrease, respectively), whereas higher values (p<0.05) of time to reach first peak (tFy1) were detected for Cr as compared to Pl (28.9 % of increase). Significant modifications (p<0.05) in muscle activation were also observed. Changes occurred in intermediary bouts, mainly in bout 2. CONCLUSION: Creatine supplementation has potential to influence biomechanical parameters related to impact control during a single session of HIIT based on running. Results indicate possible improvements in shock attenuation under creatine supplementation.

Reliability and Performance Changes with the Addition of a Cognitive Task to Static and Dynamic Postural Stability Testing

Concussions are an unfortunate consequence of sports participation. They affect motor control, neurocognitive performance, and recent reports indicate they increase the risk of lower extremity musculoskeletal injury (LEMI) upon return to sport. The increased risk of secondary LEMI may indicate the need to establish a test that is predictive of LEMI risk following return to sport. PURPOSE: Assess the between-session reliability and the effects of adding a cognitive task to static and dynamic postural stability testing. METHODS: Twelve healthy, physically active subjects (Age: 22.3 ± 2.9 years, Height: 174.4 ± 7.5 cm, Weight: 154.5 ± 28.0 lbs) participated. Subjects underwent static and dynamic postural stability testing with and without the addition of a cognitive task (Stroop task) on two separate days. Static postural stability was assessed with a single-leg balance task under eyes open (with and without the addition of the Stroop task) and eyes closed conditions. Variability of each ground reaction force component was averaged across three trials for each of the static postural stability conditions. Dynamic postural stability testing consisted of forward jump over a hurdle with a one-legged landing performed with and without the addition of the Stroop task. A stability index was calculated based on the resultant ground reaction force and each of its components. Interclass correlation coefficients (ICC, 2,1) were calculated to determine the between-session reliability of each testing condition. Comparisons were made across the static conditions and between the dynamic postural stability tasks. RESULTS: The addition of a cognitive load proved to have moderate to excellent between-session reliability for the majority of variables calculated during static (ICC values 0.74 – 0.81) and dynamic postural stability testing (ICC values 0.77 – 0.80; ML=0.800, V=0.774, DPSI=0.781). No significant differences were observed between the postural stability tasks (with or without the Stroop task). CONCLUSION: Postural stability tasks with the addition of a cognitive load prove to have moderate to excellent reliability in a healthy population. These results provide new evidence on the feasibility of dual-task postural stability testing when examining risk of LEMI following return to sport.

Vertical ground reaction force in stationary running in water and on land: A study with a wide range of cadences

Purpose: The aim of this study was to analyze the effect of cadence, immersion level as well as body density on the vertical component (Fymax) of ground reaction force (GRF) during stationary running (SR). Methods: In a controlled, laboratory study, thirty-two subjects ran at a wide range of cadences (85–210 steps/min) in water, immersed to the hip and to the chest, and on dry land. Fymax. was verified by a waterproof force measurement system and predicted based on a statistical model including cadence, immersion ratio and body density. Results: The effect of cadence was shown to depend on the environment: while Fymax increases linearly with increasing cadence on land; in water, Fymax reaches a plateau at both hip and chest immersions. All factors analyzed, cadence, immersion level and body density affected Fymax significantly, with immersion (aquatic × land environment) showing the greatest effect. In water, different cadences may lead to bigger changes in Fymax than the changes obtained by moving subjects from hip to chest immersion. A regression model able to predict 69% of Fymax variability in water was proposed and validated. Conclusion: Cadence, Immersion and body density affect Fymax in a significant and non-independent way. Besides a model of potential use in the prescription of stationary running in water, our analysis provides insights into the different responses of GRF to changes in exercise parameters between land and aquatic environment.

Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety.

External forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness. In order to establish appropriate physical conditioning regimes, which adequately prepare athletes for the loads and physical demands occurring in their sports and help reduce the risk of injury, sport-and/or discipline-specific knowledge of the external forces is needed. However, due to methodological shortcomings in biomechanical research, data comprehensively describing the external forces that occur in alpine super-G (SG) and downhill (DH) are so far lacking. Therefore, this study applied new and accurate wearable sensor-based technology to determine the external forces acting on skiers during World Cup (WC) alpine skiing competitions in the disciplines of SG and DH and to compare these with those occurring in giant slalom (GS), for which previous research knowledge exists. External forces were determined using WC forerunners carrying a differential global navigation satellite system (dGNSS). Combining the dGNSS data with a digital terrain model of the snow surface and an air drag model, the magnitudes of ground reaction forces were computed. It was found that the applied methodology may not only be used to track physical demands and loads on athletes, but also to simultaneously investigate safety aspects, such as the effectiveness of speed control through increased air drag and ski–snow friction forces in the respective disciplines. Therefore, the component of the ground reaction force in the direction of travel (ski–snow friction) and air drag force were computed. This study showed that (1) the validity of high-end dGNSS systems allows meaningful investigations such as characterization of physical demands and effectiveness of safety measures in highly dynamic sports; (2) physical demands were substantially different between GS, SG, and DH; and (3) safety-related reduction of skiing speed might be most effectively achieved by increasing the ski–snow friction force in GS and SG. For DH an increase in the ski–snow friction force might be equally as effective as an increase in air drag force.

Sit-to-stand ground reaction force characteristics in blind and sighted female children

BackgroundThe association between visual sensory and sit-to-stand ground reaction force characteristics is not clear. Impulse is the amount of force applied over a period of time. Also, free moment represents the vertical moment applied in the center of pressure (COP). Research question: How the ground reaction force components, vertical loading rate, impulses and free moment respond to long and short term restricted visual information? MethodsFifteen female children with congenital blindness and 45 healthy girls with no visual impairments participated in this study. The girls with congenital blindness were placed in one group and the 45 girls with no visual impairments were randomly divided into three groups of 15; eyes open, permanently eyes closed, and temporary eyes closed. The participants in the permanently eyes closed group closed their eyes for 20 min before the test, whereas temporary eyes closed group did tests with their eyes closed throughout, and those in the eyes open group kept their eyes open. ResultsCongenital blindness was associated with increased vertical loading rate, range of motion of knee and hip in the medio-lateral plane. Also, medio-lateral and vertical ground reaction force impulses. Similar peak negative and positive free moments were observed in three groups. Significance: In conclusion, the results reveal that sit-to-stand ground reaction force components in blind children may have clinical importance for improvement of balance control of these individuals.

Velocity-dependent transfer of adaptation in human running as revealed by split-belt treadmill adaptation.

Animal studies demonstrate that the neural mechanisms underlying locomotion are specific to the modes and/or speeds of locomotion. In line with animal results, human locomotor adaptation studies, particularly those focusing on walking, have revealed limited transfers of adaptation among movement contexts including different locomotion speeds. Running is another common gait that humans utilize in their daily lives and is distinct from walking in terms of the underlying neural mechanisms. The present study employed an adaptation paradigm on a split-belt treadmill to examine the possible independence of neural mechanisms mediating different running speeds. The adaptations learned with split-belt running resulted in aftereffects with magnitudes that varied in a speed-dependent matter. In the two components of the ground reaction force investigated, the anterior braking and posterior propulsive components exhibited different trends. The anterior braking component tended to show larger aftereffect under speeds near the slower side speed of the previously experienced split-belt in contrast to the posterior propulsive component in which the aftereffect size tended to be the largest at a speed that corresponded to the faster side speed of the split-belt. These results show that the neural mechanisms underlying different running speeds in humans may be independent, just as in human walking and animal studies.

Axial Load during the Performance of Locomotor Training in Microgravity as a Factor of Hypogravity Countermeasure Efficiency

The physiological mechanisms that determined the maintenance of human physical performance in the absence of gravity are poorly understood. The article presents the results of analysis of locomotor training characteristics of 18 cosmonauts who participated in long-term spaceflights at the International Space Station (ISS) with the duration from 175 to 201 days. The level of cosmonauts' physical performance during spaceflight was determined by the results of a locomotor test with a stepwise increasing load. The vertical components of ground reaction forces were recorded for different types of locomotion using load cells in the BD-2 treadmill. The results of determination of changes in the level of cosmonauts' physical performance during long-term spaceflight have provided the data on a higher prophylactic efficacy of locomotor training performed with an axial load of over 64% of the body weight compared to those performed with an axial load of less than 61% of the body weight. The higher countermeasure efficacy of locomotor training in the first case may be due to an increase in the intensity of stimulation of the reference input and the strengthening of the response of systems providing autonomic muscle activity.

Reference values of spatiotemporal parameters, joint angles, ground reaction forces, and plantar pressure distribution during normal gait in young women.

The aim of this study was to establish the reference values of spatiotemporal parameters, joint angles, ground reaction forces and plantar pressure distribution collected simultaneously on the same measurement path during normal gait in a homogenous group of young, healthy women. The studied group consisted of 28 healthy women aged 21 years on average. The motion capture system BTS Smart-D, 2 AMTI force platforms and Footscan pedobarographic platform were used in this research. The 14-metre measurement path and the 6-metre distance that examined women had to walk through before entering the measurement area ensured that a natural gait pattern was recorded. Statistical analysis was performed to evaluate differences between right and left lower extremities. The applied method enabled collecting several parameters regarding normal female gait biomechanics such as: spatiotemporal parameters, angle-time characteristics as well as range of motion of pelvis, hip, knee and ankle joints in gait cycle, force-time characteristics and peaks of ground reaction force components in stance phase, peak pressure and time of loading of defined foot regions in stance phase. The results may be used by clinicians, physiotherapists or researchers as a reference in diagnosing gait disorders or evaluating patient's walking pattern. In recent literature there are some disparities in gait parameters reference values even regarding similar research groups. These differences may arise from distinct method, slower or faster gait, other laboratory environment etc. This should be considered and more than one source of normative values should be checked when searching for reference data.

A New Method to Prescribe Wedges Custom Made For Individuals With Transfemoral Amputation Using Principal Component Analysis

Objective: Wedges custom made have been used to improve the gait pattern of individuals with transfemoral (TF) Amputation. However, the prescription and test of these wedges is mostly based on a highly subjective gait evaluation. The purpose of this study was to develop a rational and quantitative method to prescribe wedges custom made for the sound limb of individuals with TF using Principal Component Analysis (PCA). Method: First, the effect of different wedges was assessed in able-bodied subjects (CG). Second, using the influence of the wedges in CG, and the gait pattern of each TF individually, wedges were prescribed in order to modify their gait according to the specific effect of each wedge. The variables analyzed were the ground reaction force components and center of pressure displacement. The Mahalanobis distance for each variable and the 95% confidence interval (CI) based on CG data was calculated. Results showed, by the Mahalanobis distance of the variables, that TF subjects improved their gait pattern, TF subjects improved their gait; the variables that were out of the boundaries of 95% CI of CG, moved inside these boundaries with the use of wedges. Result: The application of wedges to the sound limb of TF amputees can improve their gait patterns, thus the application of PCA can help clinicians to decide the best device for each patient, and consequently improve TF patient quality of life.

A comparison of ground reaction force components according to the foothold heights in 16-t truck during downward step.

The aim of this study is to compare and analyze the components of ground reaction force (GRF) relative to the foothold heights during downward step of 16-t truck. Adult males (n= 10) jumped downward from each 1st, 2nd, 3rd foothold step and driver’s seat orderly using hand rail. Sampling rate of force components of 3 axis (medial-lateral [ML] GRF, anterior-posterior [AP] GRF, peak vertical force [PVF]), variables (COPx, COPy, COP area) of center of pressure (COP), loading rate, and stability index (ML, AP, vertical, and dynamic postural stability index [DPSI]) processed from GRF system was cut off at 1,000 Hz. and variables was processed with repeated one-way analysis of variance. AP GRF, PVF and loading rate showed higher value in case of not used hand rail than that used hand rail in all 1st, 2nd, and 3rd of foothold step. DPSI showed more lowered stability in order of 2nd, 3rd step than 1st foothold step used with hand rail, of which showed lowest stability from driver’s seat. COPx, COPy, and COP area showed higher value in case of 2nd and 3rd than that of 1st of foothold step, and showed lowest stability from driver’s seat. It is more desirable for cargo truck driver to utilize an available hand rail in order of 3rd, 2nd, and 1st of foothold step than downward stepping directly, thus by which may results in decrease of falling injuries and minimization of impulsive force transferring to muscular-skeletal system.

The effect of time restricted visual sensory input on asymmetry of ground reaction force components in female children

The association between visual sensory and the asymmetry index of sit-to-stand ground reaction force characteristics is not fully understood. Therefore, the purpose of this study was to investigate asymmetry index of sit-to-stand ground reaction forces, their times–to-peak, vertical loading rate, impulses, and free moment in blind and sighted children. 15 female children with congenital blindness and 30 healthy girls with no visual impairments volunteered to participate in this study. The girls with congenital blindness were placed in one group and the girls with no visual impairments were randomly divided into two groups of 15. The two condition groups consisted of, one eyes open and the other, eyes closed. The participants in the eyes closed group were asked to close their eyes for 20 min before the test, whereas those in the eyes open group kept their eyes open. Kinematic and kinetic data were collected using an eight-camera motion analysis system synchronized with two force plates embedded in the floor. A MANOVA test was run for between-group comparisons. There were no distinctive biomechanical alternations in all axes of ground reaction forces and their times-to-peak, vertical loading rate, impulses and free moments in congenital blindness and eyes closed groups compared with the eyes open group. However, eyes closed was associated with increased total time and second phase duration of sit-to-stand performance by 69% (p = 0.008) and 62% (p = 0.008), respectively. These findings reveal that individuals who are visually restricted in the short term, do not develop stereotypical movement strategies for sit-to-stand.

Steady bipedal locomotion with a forward situated whole‐body centre of mass: the potential importance of temporally asymmetric ground reaction forces

AbstractBipedalism has repeatedly evolved in many independent lineages throughout tetrapod history. Despite being widespread, the fundamental biomechanical factors involved in bipedalism remain unclear. This study experimentally investigated bipedalism in facultatively bipedal lizards and obligatorily bipedal birds to explore temporal asymmetry in the vertical component of the ground reaction force (Fz). Both lizards and birds showed significant temporal asymmetry – with higher vertical forces exerted earlier in the stance – as indicated by three different measures computed from force‐time profiles. This result parallels those reported previously for other bipedal animal groups that have a forward situated whole‐body centre of mass (COM), such as kangaroos and non‐human primates. Humans, in contrast, exhibit an orthograde posture with the COM close the hips, and show little temporal asymmetry in Fz, particularly during walking. Across a wide range of quadrupedal animals, temporal asymmetry is quite variable. Collectively, these results suggest that an ‘early‐skewed’ Fz may be an important feature of steady bipedal locomotion when the COM is forward of the hips, although an exact mechanism of cause‐and‐effect, if one exists, remains to be established. This finding has relevance for attempts at better understanding bipedal locomotion in extinct animals that likely had a COM located forward of the hips, such as carnivorous dinosaurs.

Contribution of vertical and horizontal components of ground reaction forces on global motor moment during a golf swing: a preliminary study

The swing is a crucial movement for golf performance. During their swing, golfers apply forces on the ground through their feet at the origin of the clubhead acceleration. Most of the studies that ...

A comparison and update of direct kinematic-kinetic models of leg stiffness in human running

Direct kinematic-kinetic modelling currently represents the “Gold-standard” in leg stiffness quantification during three-dimensional (3D) motion capture experiments. However, the medial-lateral components of ground reaction force and leg length have been neglected in current leg stiffness formulations. It is unknown if accounting for all 3D would alter healthy biologic estimates of leg stiffness, compared to present direct modelling methods. This study compared running leg stiffness derived from a new method (multiplanar method) which includes all three Cartesian axes, against current methods which either only include the vertical axis (line method) or only the plane of progression (uniplanar method). Twenty healthy female runners performed shod overground running at 5.0 m/s. Three-dimensional motion capture and synchronised in-ground force plates were used to track the change in length of the leg vector (hip joint centre to centre of pressure) and resultant projected ground reaction force. Leg stiffness was expressed as dimensionless units, as a percentage of an individual’s bodyweight divided by standing leg length (BW/LL). Leg stiffness using the line method was larger than the uniplanar method by 15.6%BW/LL (P < .001), and multiplanar method by 24.2%BW/LL (P < .001). Leg stiffness from the uniplanar method was larger than the multiplanar method by 8.5%BW/LL (6.5 kN/m) (P < .001). The inclusion of medial-lateral components significantly increased leg deformation magnitude, accounting for the reduction in leg stiffness estimate with the multiplanar method. Given that limb movements typically occur in 3D, the new multiplanar method provides the most complete accounting of all force and length components in leg stiffness calculation.

Evaluation of the Immediate Effect of Bracing on Gait Symmetry, Lower-Limb Kinematics, and Trunk and Pelvic Motion during Level Walking in Adolescents with Idiopathic Scoliosis

ABSTRACT Background Previous research using gait pathology in patients with adolescent idiopathic indicates gait asymmetry based on ground reaction force components, lower-limb joints, pelvic, and trunk excursion during level walking. However, evidence evaluating the effect of trunk bracing on these parameters and on symmetry of gait pattern is scarce. The aims of this study are to evaluate the range of motion of lower-limb joints as well as pelvic and trunk segments and to assess the symmetry of gait pattern in adolescents with idiopathic scoliosis when compared with normal subjects. The effect of trunk bracing on the aforementioned parameters is also investigated. Method Ten scoliotic patients (eight girls and two boys) aged between 10 and 16 years and ten normal subjects with comparable age, height, and weight were recruited for this study. A three-dimensional gait analysis system and Visual3D software were used to evaluate joint range of motion of scoliotic patients in two conditions: with and without brace, as well as from the normal subjects without brace. The symmetry of gait was assessed by use of the asymmetry index. Results The results of this study showed that scoliosis led to a decrease in frontal hip, knee, pelvic, and trunk motion. Moreover, it was shown that patients with scoliosis walk with more restricted knee, pelvic, and trunk motions in the sagittal plane. There was no significant difference between the asymmetry index value between walking with and without orthosis. In our study, it was shown that the only discrepancy in the gait pattern between scoliotic patients and healthy subjects is an asymmetrical pelvic movement in the frontal plane. Conclusion The results of this study demonstrate that trunk bracing influences the pelvic range of motion and improved symmetry of range of motions of the pelvis. However, bracing did not influence the kinematic parameters of hip, knee, and ankle joints significantly.

Ankle taping can reduce external ankle joint moments during drop landings on a tilted surface

Ankle taping is commonly used to prevent ankle sprains. However, kinematic assessments investigating the biomechanical effects of ankle taping have provided inconclusive results. This study aimed to determine the effect of ankle taping on the external ankle joint moments during a drop landing on a tilted surface at 25°. Twenty-five participants performed landings on a tilted force platform that caused ankle inversion with and without ankle taping. Landing kinematics were captured using a motion capture system. External ankle inversion moment, the angular impulse due to the medio-lateral and vertical components of ground reaction force (GRF) and their moment arm lengths about the ankle joint were analysed. The foot plantar inclination relative to the ground was assessed. In the taping condition, the foot plantar inclination and ankle inversion angular impulse were reduced significantly compared to that of the control. The only component of the external inversion moment to change significantly in the taped condition was a shortened medio-lateral GRF moment arm length. It can be assumed that the ankle taping altered the foot plantar inclination relative to the ground, thereby shortening the moment arm of medio-lateral GRF that resulted in the reduced ankle inversion angular impulse.

Approach To Analyse Of Reaction Forces In Ring–Traveller System

Abstract The paper presents the approach to analyse of reaction forces and contact pressure for ring-traveller system in twisting machine. The theory of the ballooning yarn has been adapted for the calculation of reactions, and the motion equation is developed for traveller with two reaction forces. The components of normal reaction forces are analyzed for system with free balloon and control one. The effect of the balloon control ring is shown to be significant, reducing the reaction forces of traveller or increasing the speed of spindle. Contact pressure generated between the ring and the traveller is analyzed using Hertzian contact theory. The article also presents the recommendations for optimization of the traveller shape to increase its service life.

The effect of working memory intervention on the gait patterns of the elderly

IntroductionThe purpose of this study was to evaluate the role of working memory (WM) training on walking patterns in elderly people. Methods20 elderly adults were selected and assigned randomly to two groups: WM training group and control group. WM training group received 6 weeks of computerized training on various spatial and verbal WM tasks. The spatial-temporal parameters, the ground reaction force and the timing activity of muscles in pre-posttest and in a follow-up were taken. ResultThe results indicated that a significant change in gait speed, double support time and stride time (p < 0.05). Alternations in ground reaction force (GRF) components were found significant. Timing of muscle activity also showed non-significant change after WM intervention. ConclusionBased on the results of this study, it can be concluded that WM intervention can be applied to improve gait parameters. The improvements in vertical ground reaction force after training may result in an increase upright stability and a decreased in rate falls.

Relation between peak knee flexion angle and knee ankle kinetics in single-leg jump landing from running: a pilot study on male handball players to prevent ACL injury

ABSTRACTObjectives: The relationship between knee kinematics and knee-ankle kinetics during the landing phase of single leg jumping has been widely studied to identify proper strategies for preventing non-contact ACL injury. However, there is a lack of study on knee-ankle kinetics at peak knee flexion angle during jumping from running. Hence, the purpose of this study is to establish the relationship between peak knee flexion angle, knee extension moment, ankle plantar flexion moment and ground reaction force in handball players in order to protect ACL from excessive stress during single leg jumping. In addition, the study also clarifies the role of calf muscles in relieving part of ACL stresses with different knee flexion angles during landing.Methods: Fifteen active male elite handball players of Saudi Arabia have participated in this study (Age = 22.6 ± 3.5years, Height = 182 ± 3.7 cm, Weight = 87.5 ± 10.2 kg). The players performed three successful landings of single-leg jump following running a fixed distance of about 450cm. The data were collected using a 3D motion capture and analysis system (VICON).Results: Pearson product moment correlation coefficients showed that greater peak knee flexion angle is related significantly to both lesser knee extension moment (r = -.623, P = .013) and vertical component of ground reaction force (VGRF) (r = -.688, P = .005) in landing phase. Moreover, increasing the peak knee flexion angle in landing phase tends to increase the ankle plantar flexion moment significantly (r = .832, P = .000).Conclusion: With an increase of the peak knee flexion angle during single leg jump landing from running, there would be less knee extension moment, low impact force and more plantar flexion moment. As such, the clinical implication of this study is that there may be a possible protective mechanism by increasing the knee flexion angle during landing phase, which tends to protect the ACL from vigorous strain and injuries.