Walking Ground Reaction Forces Research Articles

Modal Identification on Walking Leg Using EKF Method

The identification on the mechanical characteristic of walking leg has faced challenge due to the inconvenience installation on sensor with leg and expensive cost. This paper proposes a convenience method on identifying the leg parameters including its stiffness and damping ratio under walking state by Extend Kalman Filter (EKF) method, which only need to deal with the measured ground reaction force. Firstly, a mechanical oscillate system is used to describe the walking leg, and its corresponding dynamic governing equation is established. Then, a state-space equation is applied the governing equation and it is further inserted on the EKF method so as to set up a system update equation and measurement update equation. In addition, a solving algorithm is designed to acquire the instantaneous stiffness and damping ratio of the walking leg. Finally, a sample comprised of 760 curves of walking ground reaction force from 36 participants is employed to the identification method and the practice results demonstrate that it can efficiently discern the stiffness and damping ratio of walking leg. This study provides a novel perspective for seeking the dynamic parameters of walking leg and efficiently reduces experimental expenditure than those direct measurement of sensors installed on the surface of leg.

Design of active ankle foot orthotics for gait assistance and fall prevention

An active ankle-foot orthosis (AAFO) was developed with the intent of providing propulsive ground reaction force to individuals at risk of experiencing fall. The device makes use of one double-acting cylinder per leg, and a lever arm system to transfer propulsive force to the ground, and potentially assist in fall prevention and rehabilitation. Preliminary tests have been shown to improve ground reaction forces in walking. In this paper, the design and construction of the device is included as well as the control algorithm used and testing procedure. This research may be used to advance the field of gait assistance and fall prevention through use of active foot orthotics.

Effect of long term use of arch support foot orthoses on walking ground reaction force asymmetry index in children with flexible flat feet: A cohort study

Background: Foot orthoses are often used to correct altered gait patterns. However, effect of long term use of arch support foot orthoses on walking mechanics is not well understood. The aim of this study was to evaluate the effects of long term use of arch support foot orthoses on the asymmetry indices of ground reaction forces during stance phase of walking in male children with flexible flat feet. Methods: Fifteen male volunteered children (with their parents’ permission) with flexible flat feet were evaluated. Walking ground reaction forces and kinematic data before and after four months use of foot orthoses were recorded by force plate and Vicon motion system, respectively. Then, the asymmetry indices of ground reaction force components were calculated. Results: The results show that asymmetry index of the medio-lateral component of ground reaction force in loading response and push off phases during pre-test were higher than 4% (normal value). Also asymmetry index of its time to peak during the mid-stance phase in the pre-test were higher than normal value. Moreover, findings did not show any significant differences in asymmetry indices of other ground reaction force components and their time to peak, impulses and vertical loading rate between pre-test and post-test conditions. Conclusion: Despite the high asymmetry values of the peak medio-lateral component and it’s time to peak in children with flexible flat feet during pre-test; long-term use of the foot orthoses did not show any significant effect on the improvement of the asymmetry index of these components. However, long-term wearing of the foot orthoses reduced asymmetry index of the peak positive free moment amplitude.

Race Walking Ground Reaction Forces at Increasing Speeds: A Comparison with Walking and Running

Race walking has been theoretically described as a walking gait in which no flight time is allowed and high travelling speed, comparable to running (3.6–4.2 m s−1), is achieved. The aim of this study was to mechanically understand such a “hybrid gait” by analysing the ground reaction forces (GRFs) generated in a wide range of race walking speeds, while comparing them to running and walking. Fifteen athletes race-walked on an instrumented walkway (4 m) and three-dimensional GRFs were recorded at 1000 Hz. Subjects were asked to performed three self-selected speeds corresponding to a low, medium and high speed. Peak forces increased with speeds and medio-lateral and braking peaks were higher than in walking and running, whereas the vertical peaks were higher than walking but lower than running. Vertical GRF traces showed two characteristic patterns: one resembling the “M-shape” of walking and the second characterised by a first peak and a subsequent plateau. These different patterns were not related to the athletes’ performance level. The analysis of the body centre of mass trajectory, which reaches its vertical minimum at mid-stance, showed that race walking should be considered a bouncing gait regardless of the presence or absence of a flight phase.

Walking Ground Reaction Force Post-ACL Reconstruction: Analysis of Time and Symptoms.

The association between lower-extremity loading and clinically relevant knee symptoms at different time points after anterior cruciate ligament reconstruction (ACLR) is unclear. Vertical ground reaction force (vGRF) from walking was compared between individuals with and without clinically relevant knee symptoms in three cohorts: <12 months post-ACLR, 12-24 months post-ACLR, and >24 months post-ACLR. One hundred twenty-eight individuals with unilateral ACLR were classified as symptomatic or asymptomatic, based on previously defined cutoff values for the Knee Osteoarthritis and Injury Outcome Score (<12 months post-ACLR [symptomatic n = 28, asymptomatic n = 24]; 12-24 months post-ACLR [symptomatic n = 15, asymptomatic n = 15], and >24 months post-ACLR [symptomatic, n = 13; asymptomatic, n = 33]). Vertical ground reaction force exerted on the ACLR limb was collected during walking gait, and functional analyses of variance were used to evaluate the effects of symptoms and time post-ACLR on vGRF throughout stance phase (α = 0.05). Symptomatic individuals, <12 months post-ACLR, demonstrated less vGRF during both vGRF peaks (i.e., weight acceptance and propulsion) and greater vGRF during midstance, compared to asymptomatic individuals. Vertical ground reaction force characteristics were not different between symptomatic and asymptomatic individuals for most of stance in individuals between 12 and 24 months post-ACLR. Symptomatic individuals who were >24 months post-ACLR, exhibited greater vGRF during both peaks, but lesser vGRF during midstance, compared to asymptomatic individuals. Relative to asymptomatic individuals, symptomatic individuals are more likely to underload the ACLR limb early after ACLR (i.e., <12 months) during both vGRF peaks, but overload the ACLR limb, during both vGRF peaks, at later time points (i.e., >24 months). We propose these differences in lower-extremity loading during walking might have implications for long-term knee health, and should be considered when designing therapeutic interventions for individuals with an ACLR.

Estimation of vertical walking ground reaction force in real-life environments using single IMU sensor

Monitoring natural human gait in real-life environments is essential in many applications, including quantification of disease progression, monitoring the effects of treatment, and monitoring alteration of performance biomarkers in professional sports. Walking ground reaction forces are among the key parameters necessary for gait analysis. However, these parameters are commonly measured using force plates or instrumented treadmills which are expensive and bulky and can only be used in a controlled laboratory environment. Despite the importance of real-life gait measurement, developing reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still an open challenge, mainly due to the lack of a practical and cost-effective wearable technology for ground reaction force measurement. This paper presents a methodology to estimate the total walking ground reaction force GRFvt in the vertical direction using data from a single inertial measurement unit. Correlation analysis of the vertical acceleration of different body segments with GRFvt indicated that the 7th cervical vertebrae is one of the best locations for the sensor. The proposed method improves the accuracy of the state-of-the-art GRFvt estimation by 25%, by utilising the time-varying ratio of the vertical acceleration of the human body centre of mass and measured C7 vertical acceleration. Results of this study showed that the proposed method estimated consistently the GRFvt in both indoor and urban outdoor environment, with a 4–8% peak-to-peak normalised root mean square error.

Estimation of Tri-Axial Walking Ground Reaction Forces of Left and Right Foot from Total Forces in Real-Life Environments

Continuous monitoring of natural human gait in real-life environments is essential in many applications including disease monitoring, rehabilitation, and professional sports. Wearable inertial measurement units are successfully used to measure body kinematics in real-life environments and to estimate total walking ground reaction forces using equations of motion. However, for inverse dynamics and clinical gait analysis, the of each foot is required separately. Using an experimental dataset of 1243 tri-axial separate-foot time histories measured by the authors across eight years, this study proposes the ‘Twin Polynomial Method’ (TPM) to estimate the tri-axial left and right foot signals from the total signals. For each gait cycle, TPM fits polynomials of degree five, eight, and nine to the known single-support part of the left and right foot vertical, anterior-posterior, and medial-lateral signals, respectively, to extrapolate the unknown double-support parts of the corresponding signals. Validation of the proposed method both with force plate measurements (gold standard) in the laboratory, and in real-life environment showed a peak-to-peak normalized root mean square error of less than 2.5%, 6.5% and 7.5% for the estimated signals in the vertical, anterior-posterior and medial-lateral directions, respectively. These values show considerable improvement compared with the currently available decomposition methods in the literature.

Real-Life Measurement of Tri-Axial Walking Ground Reaction Forces Using Optimal Network of Wearable Inertial Measurement Units.

Monitoring natural human gait in real-life environment is essential in many applications including the quantification of disease progression, and monitoring the effects of treatment and alteration of performance biomarkers in professional sports. Nevertheless, reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still not available. This paper explores in detail the correlations between the acceleration of different body segments and walking ground reaction forces GRF(t) in three dimensions and proposes three sensory systems, with one, two, and three inertial measurement units (IMUs), to estimate GRF(t) in the vertical (V), medial-lateral (ML), and anterior-posterior (AP) directions. The nonlinear autoregressive moving average model with exogenous inputs (NARMAX) non-linear system identification method was utilized to identify the optimal location for IMUs on the body for each system. A simple linear model was then proposed to estimate GRF(t) based on the correlation of segmental accelerations with each other. It was found that, for the three-IMU system, the proposed model estimated GRF(t) with average peak-to-peak normalized root mean square error (NRMSE) of 7%, 16%, and 18% in V, AP, and ML directions, respectively. With a simple subject-specific training at the beginning, these errors were reduced to 7%, 13%, and 13% in V, AP, and ML directions, respectively. These results were found favorably comparable with the results of the benchmark NARMAX model, with subject-specific training, with 0% (V), 4% (AP), and 1% (ML) NRMSE difference.

Effects of obesity on lower extremity muscle function during walking at two speeds

Walking is a recommended form of physical activity for obese adults, yet the effects of obesity and walking speed on the biomechanics of walking are not well understood. The purpose of this study was to examine joint kinematics, muscle force requirements and individual muscle contributions to the walking ground reaction forces (GRFs) at two speeds (1.25ms−1 and 1.50ms−1) in obese and nonobese adults. Vasti (VAS), gluteus medius (GMED), gastrocnemius (GAST), and soleus (SOL) forces and their contributions to the GRFs were estimated using three-dimensional musculoskeletal models scaled to the anthropometrics of nine obese (35.0 (3.78kgm−2)); body mass index mean (SD)) and 10 nonobese (22.1 (1.02kgm−2)) subjects. The obese individuals walked with a straighter knee in early stance at the faster speed and greater pelvic obliquity during single limb support at both speeds. Absolute force requirements were generally greater in obese vs. nonobese adults, the main exception being VAS, which was similar between groups. At both speeds, lean mass (LM) normalized force output for GMED was greater in the obese group. Obese individuals appear to adopt a gait pattern that reduces VAS force output, especially at speeds greater than their preferred walking velocity. Greater relative GMED force requirements in obese individuals may contribute to altered kinematics and increased risk of musculoskeletal injury/pathology. Our results suggest that obese individuals may have relative weakness of the VAS and hip abductor muscles, specifically GMED, which may act to increase their risk of musculoskeletal injury/pathology during walking, and therefore may benefit from targeted muscle strengthening.

The human foot and heel–sole–toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?

Mechanically, the most economical gait for slow bipedal locomotion requires walking as an ‘inverted pendulum’, with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic ‘M’-shaped vertical ground reaction forces of walking in humans reflect this impulse–vault–impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the ‘M’-shaped walking ground reaction force profile does not require the plantigrade human foot or heel–sole–toe stance; it is maintained in tip–toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure—with ground-contacting heel behind ankle and toes in front—enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel–sole–toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all—largely avoiding the ‘cost of muscle force’—during the passive vaulting phase.

The effect of socks on vertical and anteroposterior ground reaction forces in walking and running

Background Previous research suggests that socks may have the potential for injury protection through the absorption and/or redistribution of impact forces. However, there is limited research regarding the shock attenuation qualities of athletic socks in sporting populations and previously observed pressure reductions have not been quantified using a force plate. Objective Firstly to identify the effect of specialist athletic socks on vertical and anteroposterior ground reaction forces (GRFs) during walking and running. Secondly, to compare GRFs between specialist socks, non-specialist socks and barefoot walking and running conditions. Methods Following ethical approval participants ( n = 5) completed five walking (1.52–1.68 m s −1) and running (3.8–4.2 m s −1) trials, unshod, over a force plate. This was completed before and after a 5000 m run (3.2 m s −1) in their own trainers in three conditions; barefoot, non-specialist socks and specialist running socks. Results Significant differences were identified between barefoot and specialist sock conditions for pre-intervention time to impact peak ( F = 3.110 (2), P = .05, r = .11) and maximum propulsive force ( F = 8.126 (2), P = .001, r = .25) when walking. Post hoc analysis identified an increase of .0016 s in time to impact peak when walking barefoot compared to the specialist sock condition ( T = −7.402 (4), P = .002, r = .71). During walking the specialist sock also demonstrated a significant decrease of .075 BWs in maximum propulsive force when compared to the barefoot condition ( T = −7.624 (4), P = .002, r = .79). Both significant effects diminished following the 5000 m run. Conclusion Findings suggest that the specialist running sock has limited effects on GRFs and therefore may be responsible for a limited degree of shock attenuation experienced during walking.

Effects of modified short-leg walkers on ground reaction force characteristics

Background Although short-leg walkers are often used in the treatment of lower extremity injuries (ankle and foot fractures and severe ankle sprains), little is known about the effect the short-leg walker on gait characteristics. The purpose was to examine how heel height modifications in different short-leg walkers and shoe side may affect ground reaction forces in walking. Methods Force platforms were used to collect ground reaction force data on 10 healthy participants. Five trials were performed in each of six conditions: lab shoes, gait walker, gait walker with heel insert on shoe side, gait walker modified with insert on walker side, equalizer walker, and equalizer walker with heel insert on shoe side. Conditions were randomized and walking speed was standardized between conditions. A 2 × 6 (side × condition) repeated analysis of variance was used on selected ground reaction force variables ( P < 0.05). Findings The application of a walker created peak vertical and anteroposterior ground reaction forces prior to the normal peaks associated with the loading response. Wearing a walker introduced an elevated minimum vertical ground reaction force in all conditions except the equalizer walker when compared to shoe on the shoe side. Peak propulsive anteroposterior ground reaction forces were smaller in all walker conditions compared to shoe on walker side. Interpretation The application of heel insert in gait walker with heel insert (on shoe side) and gait walker modified (on walker side) does not diminish the minimum vertical ground reaction force as hypothesized. Wearing a walker decreases the peak propulsive anteroposterior ground reaction force on the walker side and induces asymmetrical loading.

An MRI-compatible foot-loading device for assessment of internal tissue deformation

It is well known that mechanical forces acting within the soft tissues of the foot can contribute to the formation of neuropathic ulcers in people with diabetes. Presently, only surface measurements of plantar pressure are used clinically to estimate risk status due to mechanical loading. It is currently not known how surface measurements relate to the three-dimensional (3-D) internal stress/strain state of the foot. This article describes the development of a foot-loading device that allows for the direct observation of the internal deformation of foot tissues under known forces. Ground reaction forces and plantar pressure distributions during normal walking were measured in ten healthy young adults. One instant in the gait cycle, when pressure under the metatarsal heads reached a peak, was extracted for simulation in an MR imager. T 1-weighted 3-D gradient echo MRI sets were collected as the simulated walking ground reaction force was incrementally applied to the foot by the novel foot-loading device. The sub-metatarsal head soft-tissue thickness decreased rapidly at first and then reached a plateau. Peak plantar pressure measurements collected within the loading device (161±75 kPa) were lower in magnitude and less focal than pressures measured during walking (492±91 kPa). This finding implies that although the device successfully applied full peak walking ground reaction forces to the foot, they were not distributed in the same manner as during walking. Although not representative of gait, the data collected from this in vivo mechanical test are suitable for determination of foot tissue material properties or, when combined with finite element modeling, to examine the relationship between surface loading and internal stress.

A computerized system for real-time visualization of ground reaction forces in walking

A computerized system for real-time visualization of ground reaction forces in walking