Ground Reaction Force Characteristics Research Articles

A support vector machine approach to detect trans-tibial prosthetic misalignment using 3-Dimensional ground reaction force features: A proof of concept

Prosthetists conventionally evaluate alignment based on visual interpretation of patients' gait, which is convenient, but largely subjective and depends on prosthetists' experience. In this paper, we explore the feasibility of using a support vector machine (SVM) approach to automatically detect misalignment of trans-tibial prostheses through ground reaction force (GRF). Alternate classification algorithms with varying kernels and feature sets were compared to assess the suitability for detection of a representative misalignment (six degrees of ankle plantar flexion) from normal alignment. A classical feature selection algorithm, Fisher Score, was further introduced to identify valuable features and reduce the dimension of feature sets. The SVMs achieved a detection accuracy of 96.67% at best within the same subject and 88.89%, respectively, for inter-subject. Combined horizontal and vertical components of GRF features provided the maximum detection accuracies. Propulsion peak force was identified as key variable of gait for misalignment prediction. As a proof of concept, the results demonstrate potential in applying this approach to detect prosthetic misalignment based on gait patterns, and is a step towards future developments of tools for early prevention of misalignment in clinical.

The Relationship Between the Push Off Ground Reaction Force and Ball Speed in High School Baseball Pitchers.

Oyama, S and Myers, JB. The relationship between the push off ground reaction force and ball speed in high school baseball pitchers. J Strength Cond Res 32(5): 1324-1328, 2018-Baseball pitching is a sequential movement that requires transfer of momentum from the lower extremity to the throwing arm. Therefore, the ground reaction force (GRF) during push off is suggested to play a role in production of ball speed. The purpose of this study was to investigate the correlation between GRF characteristics during push off and ball speed in high school baseball pitchers. A total of 52 pitchers performed fast pitches from an indoor pitching mound. A force plate embedded in an indoor mound was used to capture the push off GRF. The GRF characteristics (peak anterior, vertical, and resultant forces, vertical and resultant forces at the time of peak anterior GRF, and impulse produced by the anterior GRF) from the 3 fastest strike pitches from each pitcher were used for analyses. Spearman's rank correlation coefficients were used to describe the relationships between ball speed and the GRF characteristics. Ball speed was only weakly correlated with peak resultant force (ρ = 0.32, p = 0.02) and vertical (ρ = 0.45, p < 0.001) and resultant (ρ = 0.42, p = 0.002) forces at the time of peak anterior force. The ball speed was not correlated with other variables. The correlation between ball speed and push off force in high school pitchers was weak, especially when compared with what was reported for adult pitchers in other studies. Unlike for adult pitchers, higher push off force is only weakly correlated with ball velocity in high school pitchers, which suggests that training to better use body momentum may help high school pitchers improve ball speed.

Vertical Ground Reaction Force Gait Patterns During Walking in Children with Autism Spectrum Disorders

The characteristics of vertical ground reaction force (VGRF) gait patterns in children with autism spectrum disorders (ASD) are poorly understood. The purpose of this study was to identify VGRF gait features that discriminate between children with ASD and the peer control group. The VGRF data were obtained from 30 children with ASD and 30 normal healthy children aged 4 to 12 years. A three-dimensional motion analysis system with eight cameras and two force plates were used to collect VGRF data while subjects performed self-selected speed of barefoot walking. Parameterization techniques were applied to VGRF waveforms to extract the VGRF gait features. Mean significant differences between the two groups were tested using independent samples t-test and Mann-Whitney U test. Significant group differences were found for four VGRF gait features. Results indicated that children with ASD exhibited a significant reduction of the second peak of VGRF, earlier relative time to the occurrence of the second peak of VGRF, lower push-off rate, and higher peak ratio of the two VGRF peaks during normal speed of walking. These prominent differences showed that children with ASD had difficulties in supporting their body weight during terminal stance phase and these conditions affect the gait instability. The findings of this study develop further understanding of VGRF gait patterns that significantly differentiate between children with ASD and the peer control groups.

The Relationship Between Vertical Ground Reaction Force And Audio Characteristics During A Single-Leg Landing

The Relationship Between Vertical Ground Reaction Force And Audio Characteristics During A Single-Leg Landing

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.

Mechanical Fatigue of Bovine Cortical Bone Using Ground Reaction Force Waveforms in Running.

Stress fractures are a common overuse injury among runners associated with the mechanical fatigue of bone. Several in vivo biomechanical studies have investigated specific characteristics of the vertical ground reaction force (vGRF) in heel-toe running and have observed an association between increased loading rate during impact and individuals with a history of stress fracture. The purpose of this study was to examine the fatigue behavior of cortical bone using vGRF-like loading profiles, including those that had been decomposed into their respective impact and active phase components. Thirty-eight cylindrical cortical bone samples were extracted from bovine tibiae and femora. Hydrated samples were fatigue tested at room temperature in zero compression under load control using either a raw (n = 10), active (n = 10), low impact (n = 10), or high impact (n = 8) vGRF profile. The number of cycles to failure was quantified and the test was terminated if the sample survived 105 cycles. Fatigue life was significantly greater for both impact groups compared to the active (p < 0.001) and raw (p < 0.001) groups, with all low impact samples and 6 of 8 high impact samples surviving 105 cycles. The mean (± SD) number of cycles to failure for the active and raw groups was 12,133±11,704 and 16,552±29,612, respectively. The results suggest that loading rates associated with the impact phase of a typical vGRF in running have little influence on the mechanical fatigue behavior of bone relative to loading magnitude, warranting further investigation of the mechanism by which increased loading rates are associated with stress fracture.

Robust Ground Reaction Force Estimation and Control of Lower-Limb Prostheses: Theory and Simulation

Ground reaction force (GRF) characteristics of amputee walking are important for the analysis of clinical gait data, and also to update model reference adaptive impedance (MRAI) controllers. GRF estimation is a better alternative than direct GRF measurement because of the disadvantages of load cells, such as high cost, integration difficulties due to weight and physical dimensions, the possibility of overload, and measurement noise. This paper presents four robust MRAI observer/controller combinations for GRF estimation-based control of a prosthesis and a legged robot model in the presence of parametric uncertainties and unmodeled dynamics, in which the robot model is employed to mimic able-bodied walking. Since unknown GRFs can reduce the performance of prosthesis control systems, the proposed MRAI controllers are designed to compensate their effects. All four proposed observer/controller combinations enable the system to imitate the biomechanics of able-bodied walking as defined by mechanical impedance, and provide flexible and smooth gait. Lyapunov analysis of the observer/controller combinations is used to prove stability. The four MRAI controllers are compared with each other from the perspective of GRF estimation accuracy, prosthetic knee angle tracking accuracy, parameter estimation accuracy, control effort, and computational effort. Simulation results show that all four MRAI controllers achieve good tracking performance, stable limit cycles, and accurate GRF estimation.

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.

Ground Reaction Forces During Sprinting in Unilateral Transfemoral Amputees.

Understanding the characteristics of ground reaction forces (GRFs) on both limbs during sprinting in unilateral amputees wearing running-specific prostheses would provide important information that could be utilized in the evaluation of athletic performance and development of training methods in this population. The purpose of this study was to compare GRFs between intact and prosthetic limbs during sprinting in unilateral transfemoral amputees wearing running-specific prostheses. Nine sprinters with unilateral transfemoral amputation wearing the same type of prosthesis performed maximal sprinting on a 40-m runway. GRFs were recorded from 7 force plates placed in the center of the runway. Peak forces and impulses of the GRFs in each direction were compared between limbs. Peak forces in vertical, braking, propulsive, and medial directions were significantly greater in intact limbs than those in prosthetic limbs, whereas there were no significant differences in peak lateral force between limbs. Further, significantly less braking impulses were observed in prosthetic limbs than in intact limbs; however, the other measured impulses were not different between limbs. Therefore, the results of the present study suggest that limb-specific rehabilitation and training strategies should be developed for transfemoral amputees wearing running-specific prostheses.

A prospective comparison of lower extremity kinematics and kinetics between injured and non-injured collegiate cross country runners

Collegiate cross country runners are at risk for running related injuries (RRI) due to high training volume and the potential for aberrant lower extremity biomechanics. However, there is a need for prospective research to determine biomechanical risk factors for RRI. The purpose of this study was to prospectively compare ankle, knee, and hip kinematics and kinetics and ground reaction force characteristics between injured and non-injured cross country runners over a 14-week season. Biomechanical running analyses were conducted on 31 collegiate-cross country runners using a 3-dimensional motion capture system and force plate prior to the start of the season. Twelve runners were injured and 19 remained healthy during the course of the season. Peak external knee adduction moment (KAM), a surrogate for frontal plane knee loading, and peak ankle eversion velocity were greater in runners who sustained an injury compared to those who did not, and no differences were noted in ground reaction force characteristics, or hip kinematics and kinetics. Reducing the KAM and ankle eversion velocity may be an important aspect of preventing RRI.

Gait ground reaction force characteristics in deaf and hearing children

The link between gait parameters and hearing loss is not well understood. The objective of this study was to investigate the effects of the gait ground reaction forces, their time to peak, vertical loading rate, impulses and free moment during gait in deaf and hearing children. Thirty male children were equally divided into a healthy group and a group with hearing loss problems (Deaf group). Ground reaction forces were analyzed during barefoot walking. MANOVA test was used for between group comparisons. The significance level was set at p<0.05 for all analyses. Hearing loss was associated with increased propulsion lateral-medial ground reaction force (p=0.031), its time to peak (p=0.008), and lateral- medial impulse (p=0.018). Similar vertical reaction forces were observed in both groups (p>0.05). Positive peak of free moments in the healthy group was significantly greater than that in the deaf group (p=0.004). In conclusion, the results reveal that gait ground reaction force components in deaf children may have clinical values for rehabilitation of these subjects.

Limb dominance, foot orientation and functional asymmetry during walking gait

While healthy gait is often characterized as, or assumed to be symmetric, consistent asymmetries often exist. In this study, we test the hypotheses that asymmetries in lower limb function, as measured by ground reaction force characteristics, may be explained by differences in foot orientation or limb dominance. Peak ground reaction force (GRF) measurements, and impulses were obtained for thirty-six healthy subjects with simultaneous kinematic estimates of foot posture. Three gait tasks were performed: subjects walked i) with normal foot orientation, ii) with feet laterally rotated (outward), and iii) with feet aligned in the direction of movement (straight). All subjects reported right limb dominance. Our results indicate that vertical, braking and propulsive GRF components are largely symmetrical, but significant asymmetries exist in the mediolateral peak forces and impulses with higher lateral and lower medially-directed GRF components being generated by the dominant right limbs. While foot orientations used during the different tasks do explain some differences in mediolateral peak forces and impulses, foot orientation did not explain this variation within normal walking. We conclude that limb dominance is a better predictor of asymmetry in force generation than foot posture.

Relationship between preparation to take off and ground reaction force characteristics in male long jumpers

Subjects: Six national level male long jumpers (age: 22.30±2.20, height:1.84±0.027, weight :73.5±6.65, personal best:6.54± 0.42 ) were participated in the current study ,aftar an appropriate warm up every jumper had three trails. The best trial of each of the six subjects was analyzed in obtaining kinematic and kinetic data. Data were obtained only when the performer was in contact with the force platform. The study was conducted in an outdoor track in the faculty of physical education, Alexandria University .The study procedures began when all jumpers declared themselves ready to begin, the participants performed without spikes on their shoes in order to protect their feet from the shock of hitting a hard metal take off plate located beneath the covering. Conclusion Although the importance of takeoff phase for generating the appropriate force in long jump, the preparation to takeoff phase also plays an important role at the same moment .the adjustment of final steps obviously serves him to bring his foot in a position that facilitates the development of vertical force and velocity at takeoff his final steps before takeoff to reach the optimum position for force production. Longer ground contact time during takeoff is necessary to develop a large amount of vertical force which is needed to maximize the magnitude of vertical velocity. As a consequence of applying the vertical loading force over a longer duration is that the rate at which the force is developed is small. So training programs should include technical exercises to optimize the preparation phase of takeoff, also coaches should design special exercises to maximize leg stiffness during takeoff.

Reliability and Repeatability of Countermovement Jump Waveforms

Though the countermovement vertical jump (CMJ) has traditionally been used to assess lower body force and power, the force-time characteristics of the CMJ ground reaction force (GRF) waveform may be of value in predicting injury risk and assessing training readiness. Prior to evaluating the CMJ GRF waveform as a diagnostic and evaluative tool, the reliability of the waveform on a within and between day basis should be established. PURPOSE: To determine the within day and between day reliability of the CMJ GRF waveform in healthy individuals. METHODS: Twenty-five healthy (age = 21.5 ± 1.9 years), recreationally active men and women completed one familiarization and three experimental visits, a minimum of 48 hours apart. Each visit consisted of a brief, standardized warmup, two submaximal CMJs, and three maximal CMJs performed on a force plate (sample rate = 1000Hz). Each jump was separated by two minutes. To reduce the variability associated with arm swing, all jumps were performed with subjects’ hands on their hips. The CMJ GRF waveform for each jump, beginning with the minimum GRF during the counter-movement and ending at take off, was interpolated and re-sampled to a uniform length of 1000 data points. Individual within and between day reliabilities for each subject’s waveform shapes were calculated using the adjusted coefficient of multiple determination (R2a) as previously described by Kadaba et al (J Orthop Res, 7(6): 849-860, 1989). Briefly, the primary calculation of the within day reliability compared the GRF at each data point of a single jump with the mean GRF for that day at the corresponding data point. The between day reliability was calculated similarly, however, the mean GRF at each point for each day was compared to the mean GRF at that point of all three days. Data is reported as the coefficient of multiple correlation (CMC), the positive square root of the R2a. RESULTS: The CMJ waveforms were highly reliable, both on a within day (0.968 ± 0.020) and between day (0.962 ± 0.018) basis. Observed within day CMC values ranged from 0.909 – 0.993, whereas between day CMC values ranged from 0.917 – 0.994. CONCLUSION: Individual CMJ GRF waveforms are highly reliable under these test conditions. These results provide preliminary evidence that the CMJ GRF waveforms shapes may have utility as a diagnostic and evaluative tool.

Prosthetic foot design optimisation based on roll-over shape and ground reaction force characteristics

Most prosthetic foot products are adjusted by skilled prosthetists using a variety of gait analysis and information given to them by patients in terms of feel and experience. The design of prosthetic foot has traditionally focused on optimising stiffness to support the body weight and storage/release mechanisms of strain energy from heel contact to push off. As a result of this, the optimisation process of a prosthetic foot is simple and sometimes insufficient. It is proposed that the stiffness and energy release mechanisms of prosthetic feet be designed to satisfy amputee’s natural gait characteristics that are defined by an effective roll-over shape and corresponding ground reaction force combinations. Each point on the roll-over shape is mapped with a ground reaction force corresponding to its time stamp. The resulting discrete set of ground reaction force components are applied to the prosthetic foot sole and its stiffness profile is optimised to produce a desired deflection as given by the corresponding point on the roll-over shape. The robustness of this novel computational method is tested on three prosthetic designs. The mesh sensitivity results and the discretisation error resulting from applying finite number of ground reaction forces are discussed. It is shown that the proposed methodology is able to provide valuable insights in the guidelines for selection of materials for a multi-material prosthetic foot.

Gait ground reaction force characteristics of low back pain patients with pronated foot and able-bodied individuals with and without foot pronation

The link between gait parameters and foot abnormalities in association with low back pain is not well understood. The objective of this study was to investigate the effects of excessive foot pronation as well as the association of LBP with excessive foot pronation on the GRF components during shod walking. MethodsForty-five subjects were equally divided into a control group, a group of subjects with pronated feet only, and another group with pronated feet and LBP. Ground reaction forces were analyzed during shod walking. ResultsFoot pronation without low back pain was associated with increased lateral-medial ground reaction force, impulse, and time to peak of all reaction forces in heel contact phase (p<0.03). In low back pain patients with pronated foot, greater vertical reaction forces (p=0.001) and loading rate, and time to peak on propulsion force were observed compared to pronated foot without low back pain group. Impulse in posterior-anterior reaction force was smaller in the able-bodied group with normal foot than in the other groups (p<0.05). Positive peak of free moments of the LBP group was significantly greater than that in other groups (p<0.05). In conclusion, foot pronation alone was not associated with elevated vertical ground reaction forces. While, low back pain patients with foot pronation displayed higher vertical ground reaction force as well as higher loading rate. Present results reveal that gait ground reaction force components in low back pain patients with pronated foot may have clinical values on the prognosis and rehabilitation of mechanical LBP patients.

Bilateral and unilateral vertical ground reaction forces and leg asymmetries in soccer players

The purposes of this study were to assess unilateral and bilateral vertical jump performance characteristics, and to compare the vertical ground reaction force characteristics of the impulse and landing phase of a vertical jump between the dominant and non-dominant leg in soccer players. The sample consisted of 20 male soccer players (22.80 ± 2.71 years, 1.88 ± 0.06 m, 76.47 ± 8.80 kg) who competed in the third division of the Spanish football league. Vertical jump performance was determined by testing the impulse and landing phase of a bilateral vertical jump, dominant leg vertical jump and non-dominant leg vertical jump. Significant differences (p < 0.05) between dominant and non-dominant legs were found in counter movement jump (CMJ) flight time (LA = -2.38%, d = 0.33), CMJ flight height (LA = -4.55%, d = 0.33) and CMJ speed take-off (LA = -2.91%, d = 0.42). No significant differences were found between the dominant and non-dominant leg in the F1 and F2 magnitudes during the landing phase, the time from the first contact of the foot with the ground to the production of F1, the time from the second contact of the foot with the ground to the production of F2, and the time to stabilization of the landing phase. Although differences were found between the dominant and non-dominant leg in the impulse phase of the jump, no significant differences were found between dominant and non-dominant legs in the landing phase of vertical jump variables.

보행 시 농작업 종사자들의 슬관절 퇴행성 등급에 따른 지면반력 특성 분석

Objective : This study was conducted with an aim to use it as basic data for developing assistive devices, such as insoles that can suppress the progress of degenerative diseases and strategies, to improve early degenerative diseases by assessing walking characteristics of farm workers who were classified as KL-grade in the perspective of motor mechanics. Method : 38 male and female adults who complained of knee joint pain for more than six months were selected, and they were classified according to KL-grade. KL-grade was assessed by an orthopaedic specialist and an occupational environment health specialist. Filming equipment (FX-1, CASIO, Japan) and a ground reaction force system (AMTI OR6, AMTI, USA) were used to identify ground reaction force characteristics, and WOMAC was used for a pain rating scale. Results : There was a difference between the right and left side (axis-X) according to KL-grade, and when the grade was higher, the internal ground reaction force was also higher. Changes in COP were not affected by KL-grade of the knee joint, but it tended to increase as the grade increased. There were differences in the time required for limb support while walking according to the grades, and when the grade was higher, walking was more inefficient with long braking force and short propulsion forces. Also, pain rating scale, the right and left side, and COP changes while in support phase were related. Conclusion : There was a partial, statically significant difference in KL-grade and ground reaction force occurring during the support phase, and there were differences in ground reaction forces according to the grades of degenerative arthritis in the knee joint, indicating that this study is worthy as basic data for future studies.

Verbal Instructions Acutely Affect Drop Vertical Jump Biomechanics--Implications for Athletic Performance and Injury Risk Assessments.

Biomechanical quantities acquired during the drop vertical jump (DVJ) are used in the assessment of athletic performance and injury risk. The objective was to examine the impact of different verbal instructions on spatiotemporal, kinematic, and kinetic variables commonly included in such assessments. Ten men and 10 women from local varsity and club volleyball, basketball, figure skating, and track and field teams volunteered to participate. The athletes performed DVJs after given instructions to minimize ground contact time (CT), maximize jump height (HT), and synchronously extend the lower extremity joints (EX). Between the CT, HT, and EX conditions, body segment and joint angles were compared together with characteristics of vertical ground reaction force (GRF), whole-body power output, stiffness, and center-of-mass displacement time histories. Verbal instructions were found to influence nearly all of the spatiotemporal, body segment and joint kinematic, and kinetic variables that were statistically analyzed. Particularly noteworthy was the finding that athletic performance indices (e.g., jump height, power output, vertical stiffness, and reactive strength index) and lower extremity injury risk markers (e.g., peak vertical GRF and frontal plane knee angle) were significantly different (p ≤ 0.05) between the CT, HT, and EX conditions. The findings of this study suggest that verbal instructions should be controlled and/or clearly documented when using the DVJ to assess athletic performance potential and injury risk. Moreover, practitioners who devise performance enhancement and injury prevention strategies based on DVJ assessments are advised to consider that "coaching" or "cueing" during the task execution could impact conclusions drawn.

Kinematic and Ground Reaction Force Characteristics of Goalie-Independent and Goalie-Dependent Soccer Penalty Kicks

Kinematic and Ground Reaction Force Characteristics of Goalie-Independent and Goalie-Dependent Soccer Penalty Kicks