Anterior Ground Reaction Force Research Articles

The effect of impaired unilateral ankle propulsion on contralateral knee joint loading

BackgroundImpairments in unilateral ankle propulsion may result from restriction by an external device or pathology such as lower limb amputation. Models of gait suggest this reduction may lead to increased collisional force on the contralateral side, potentially increasing force through the knee and increasing the risk of knee pain or osteoarthritis. Research QuestionHow do restrictions in unilateral ankle propulsive force affect contralateral knee joint loading in otherwise healthy individuals? Methods18 individuals without impairment walked on a treadmill at 1.5m/s for two conditions: one free of restrictions, and one where a randomized limb’s ankle propulsive force was restricted using an off-the-shelf ankle-foot orthosis (AFO). Ankle propulsive power, lower extremity joint work, and ground reaction force variables were calculated for the final 3 gait cycles of each condition. Tibiofemoral joint contact force (TJCF) for the limb contralateral to the AFO was calculated through a standard OpenSim workflow utilizing the gait2392 model. Intra-limb pair-wise comparisons were made between conditions. ResultsCompared to walking unrestricted, the limb wearing the AFO demonstrated a significant reduction in peak ankle propulsive power and positive ankle work by approximately 50% each (p<0.01). With ankle restriction, the ipsilateral knee significantly increased positive work (p<0.01). The overall propulsion produced by that limb did not change between conditions, demonstrated by a lack of change in anterior ground reaction force impulse (p=0.11). The knee of the limb contralateral to the AFO did not display differences in any TJCF variable between conditions (all p>0.07). SignificanceThese results suggest a unilateral deficit in ankle propulsion will not increase contralateral knee joint forces in individuals who are able to use other joints of the limb to compensate for the loss of ankle function. However, further research should investigate this relationship in those who display pathologies that may prevent more proximal compensations.

Visual feedback improves propulsive force generation during treadmill walking in people with Parkinson disease

Persons with Parkinson's disease experience gait alterations, such as reduced step length. Gait dysfunction is a significant research priority as the current treatments targeting gait impairment are limited. This study aimed to investigate the effects of visual biofeedback on propulsive force during treadmill walking in persons with Parkinson's. Sixteen ambulatory persons with Parkinson's participated in the study. They received real-time biofeedback of anterior ground reaction force during treadmill walking at a constant speed. Peak propulsive force values were measured and normalized to body weight. Spatiotemporal parameters were also assessed, including stride length and double support percent. Persons with Parkinson's significantly increased peak propulsive force during biofeedback compared to baseline (p <.0001, Cohen's dz = 1.69). Variability in peak anterior ground reaction force decreased across repeated trials (p <.0001, dz = 1.51). While spatiotemporal parameters did not show significant changes individually, stride length and double support percent improved marginally during biofeedback trials. Persons with Parkinson's can increase propulsive force with visual biofeedback, suggesting the presence of a propulsive reserve. Though stride length did not significantly change, clinically meaningful improvements were observed. Targeting push-off force through visual biofeedback may offer a potential rehabilitation technique to enhance gait performance in Persons with Parkinson's. Future studies could explore the long-term efficacy of this intervention and investigate additional strategies to improve gait in Parkinson's disease.

Effects of peak ankle dorsiflexion angle on lower extremity biomechanics and pelvic motion during walking and jogging.

Ankle dorsiflexion during walking causes the tibia to roll forward relative to the foot to achieve body forward. Individuals with ankle dorsiflexion restriction may present altered movement patterns and cause a series of dysfunction. Therefore, the aim of this research was to clearly determine the effects of peak ankle dorsiflexion angle on lower extremity biomechanics and pelvic motion during walking and jogging. This study involved 51 subjects tested for both walking and jogging. The motion capture system and force measuring platforms were used to synchronously collect kinematics and kinetics parameters during these activities. Based on the peak ankle dorsiflexion angle during walking, the 51 subjects were divided into a restricted group (RADF group, angle <10°) and an ankle dorsiflexion-unrestricted group (un-RADF group, angle >10°). Independent-Sample T-tests were performed to compare the pelvic and lower limb biomechanics parameters between the groups during walking and jogging test on this cross-sectional study. The parameters that were significantly smaller in the RADF group than in the un-RADF group at the moment of peak ankle dorsiflexion in the walking test were: ankle plantar flexion moment (p < 0.05), hip extension angle (p < 0.05), internal ground reaction force (p < 0.05), anterior ground reaction force (p < 0.01), pelvic ipsilateral tilt angle (p < 0.05). In contrast, the external knee rotation angle was significantly greater in the RADF group than in the un-RADF group (p < 0.05). The parameters that were significantly smaller in the RADF group than in the un-RADF group at the moment of peak ankle dorsiflexion in the jogging test were: peak ankle dorsiflexion angle (p < 0.01); the anterior ground reaction force (p < 0.01), the angle of pelvic ipsilateral rotation (p < 0.05). This study shows that individuals with limited ankle dorsiflexion experience varying degrees of altered kinematics and dynamics in the pelvis, hip, knee, and foot during walking and jogging. Limited ankle dorsiflexion alters the movement pattern of the lower extremity during walking and jogging, diminishing the body's ability to propel forward, which may lead to higher injury risks.

Comparison of foot kinematics and ground reaction force characteristics during walking in individuals with highly and mildly pronated feet

BackgroundIndividuals with highly pronated feet (PF) are more prone to lower extremity injuries than those with mildly PF. However, whether foot kinematics and ground reaction force (GRF) characteristics differ according to the severity of PF deformity is unclear. Research questionAre there differences in foot kinematics and GRF characteristics during walking between individuals with mildly PF and those with highly PF? MethodsTen individuals with mildly PF and 10 with highly PF (six-item foot posture index scores: 6–9 and 10–12 points, respectively) participated in this study. A three-dimensional motion analysis system measured participants’ foot kinematics and GRF characteristics during gait trials. ResultsParticipants with highly PF exhibited significantly lower medial longitudinal arch heights than those with mildly PF from 0 % to 90 % of the stance phase (p < 0.05). No significant differences were observed in any of the angles between the foot segments. Additionally, participants with highly PF exhibited significantly larger posterior GRF than those with mildly PF from 2 % to 7 % of the stance phase (p < 0.05). Participants with highly PF also exhibited significantly larger anterior GRF than those with mildly PF, from 62 % to 82 % of the stance phase (p < 0.05). SignificanceThe results of this study suggest that the more severe the PF deformity, the more inefficient the foot ground force transmission, and the stronger the load applied to the foot. These results may be related to the higher incidence of lower extremity injuries in individuals with highly PF than in those with mildly PF.

Hybrid and adaptive control of functional electrical stimulation to correct hemiplegic gait for patients after stroke.

Introduction: Gait, as a fundamental human movement, necessitates the coordination of muscles across swing and stance phases. Functional electrical stimulation (FES) of the tibialis anterior (TA) has been widely applied to foot drop correction for patients with post-stroke during the swing phase. Although the gastrocnemius (GAS) during the stance phase is also affected, the Functional electrical stimulation of the gastrocnemius received less attention. Methods: To address this limitation, a timing- and intensity-adaptive Functional electrical stimulation control strategy was developed for both the TA and GAS. Each channel incorporates a speed-adaptive (SA) module to control stimulation timing and an iterative learning control (ILC) module to regulate the stimulation intensity. These modules rely on real-time kinematic or kinetic data during the swing or stance phase, respectively. The orthotic effects of the system were evaluated on eight patients with post-stroke foot drop. Gait kinematics and kinetics were assessed under three conditions: no stimulation (NS), Functional electrical stimulation to the ankle dorsiflexor tibialis anterior (SA-ILC DS) and FES to the tibialis anterior and the ankle plantarflexor gastrocnemius (SA-ILC DPS). Results: The ankle plantarflexion angle, the knee flexion angle, and the anterior ground reaction force (AGRF) in the SA-ILC DPS condition were significantly larger than those in the NS and SA-ILC DS conditions (p < 0.05). The maximum dorsiflexion angle during the swing phase in the SA-ILC DPS condition was similar to that in the SA-ILC DS condition, with both being significantly larger than the angle observed in the NS condition (p < 0.05). Furthermore, the angle error and force error relative to the set targets were minimized in the SA-ILC DPS condition. Discussion: The observed improvements can be ascribed to the appropriate stimulation timing and intensity provided by the SA-ILC DPS strategy. This study demonstrates that the hybrid and adaptive control strategy of functional electrical stimulation system offers a significant orthotic effect, and has considerable potential for future clinical application.

Gait speed and individual characteristics are related to specific gait metrics in neurotypical adults

Gait biofeedback is a well-studied strategy to reduce gait impairments such as propulsion deficits or asymmetric step lengths. With biofeedback, participants alter their walking to reach the desired magnitude of a specific parameter (the biofeedback target) with each step. Biofeedback of anterior ground reaction force and step length is commonly used in post-stroke gait training as these variables are associated with self-selected gait speed, fall risk, and the energy cost of walking. However, biofeedback targets are often set as a function of an individual’s baseline walking pattern, which may not reflect the ideal magnitude of that gait parameter. Here we developed prediction models based on speed, leg length, mass, sex, and age to predict anterior ground reaction force and step length of neurotypical adults as a possible method for personalized biofeedback. Prediction of these values on an independent dataset demonstrated strong agreement with actual values, indicating that neurotypical anterior ground reaction forces can be estimated from an individual’s leg length, mass, and gait speed, and step lengths can be estimated from individual’s leg length, mass, age, sex, and gait speed. Unlike approaches that rely on an individual’s baseline gait, this approach provides a standardized method to personalize gait biofeedback targets based on the walking patterns exhibited by neurotypical individuals with similar characteristics walking at similar speeds without the risk of over- or underestimating the ideal values that could limit feedback-mediated reductions in gait impairments.

Association of Ground Reaction Force Measurements in Runners with Symptomatic Iliotibial Band Friction Syndrome: A Cross-Sectional Study

Iliotibial band syndrome (ITBS) is a common running related injury. While previous studies have evaluated the relationship between biomechanical variables and ITBS, most have found limited evidence, particularly with measures related to ground reaction force (GRF). The purpose of this study was to use a classification and regression tree (CART) analysis to determine whether the combination of GRF measures would be strongly associated in runners with ITBS. A cross-sectional study was performed at an outpatient center focused on running injuries. A convenience sample of 52 runners with ITBS, assessed between September 2012 and July 2022, were evaluated for eligibility, from which, 30 rearfoot strike runners with ITBS and no secondary running-related injuries were selected. Injured runners were matched to 30 healthy controls from a normative database. Each ran on an instrumented treadmill at a self-selected speed. GRF variables were calculated, including peak GRFs, loading rates, and impulses. CART analysis was performed to identify interactions between GRF data and runners with ITBS. An ROC curve was executed, to determine the accuracy of the model. Posterior GRF impulse (PGRFI), anterior GRF (AGRFI), peak anterior GRF (PAGRF), and vertical stiffness at initial loading (VSIL) all emerged as variables associated with ITBS in the CART analysis. The model was able to correctly identify 25 (83.3%) runners with ITBS and 25 (83.3%) controls. The area under the ROC curve (accuracy) was 0.87 (95% CI, 0.77–0.96; SE, 0.04; p &lt; 0.001). In conclusion, interactions between GRF variables were associated with ITBS in runners. The best classification included interactions between PGRFI, AGRFI, AGRFP, and VSIL, using specific cut-off values. Loading rates were not independently associated with ITBS.

Timing of propulsion-related biomechanical variables is impaired in individuals with post-stroke hemiparesis

BackgroundIn individuals with post-stroke hemiparesis, reduced paretic leg propulsion, measured through anterior ground reaction forces (AGRF), is a common and functionally-relevant gait impairment. Deficits in other biomechanical variables such as plantarflexor moment, ankle power, and ankle excursion contribute to reduced propulsion. While reduction in the magnitude of propulsion post-stroke is well studied, here, our objective was to compare the timing of propulsion-related biomechanical variables. Research questionAre there differences in the timing of propulsion and propulsion-related biomechanical variables between able-bodied individuals, the paretic leg, and non-paretic leg of post-stroke individuals? MethodsNine able-bodied and 13 post-stroke individuals completed a gait analysis session comprising treadmill walking trials at each participant’s self-selected speed. Two planned independent sample t-tests were conducted to detect differences in the timing of dependent variables between the paretic versus non-paretic leg post-stroke and paretic leg versus the dominant leg of able-bodied individuals. ResultsPost-stroke individuals demonstrated significantly earlier timing of peak AGRF of their paretic leg versus their non-paretic leg and able-bodied individuals. Post-stroke participants displayed earlier timing of peak power of their paretic leg versus their non-paretic leg and able-bodied individuals, and earlier timing of peak ankle moment of the paretic leg versus able-bodied. No significant differences were detected in the timing of peak ankle angle. SignificanceThe earlier onset of peak AGRF, peak ankle power, and peak ankle moment may be an important, under-studied biomechanical factor underlying stroke gait impairments, and a potential therapeutic target for stroke gait retraining. Future investigations can explore the use of interventions such as gait biofeedback to normalize the timing of these peaks, thereby improving propulsion and walking function post-stroke.

Gait asymmetries are exacerbated at faster walking speeds in individuals with acute anterior cruciate ligament reconstruction.

Previous research suggests more biomechanically demanding tasks (e.g., stair descent, hopping) magnify biomechanical asymmetries compared with walking after anterior cruciate ligament (ACL) reconstruction. However, it is unclear if modifying task-specific constraints, like walking speed also elicits greater biomechanical asymmetries in this population. We examined the effects of manipulating walking speed on ground reaction force (GRF) asymmetries in individuals with ACL reconstruction and uninjured controls. Thirty individuals with ACL reconstruction (age = 20.6 ± 5.4 years, body mass index [BMI] = 23.9 ± 3.3 kg/m2 ) and 15 controls (age = 23.1 ± 4.5 years, BMI = 23.6 ± 2.7 kg/m2 ) were tested on an instrumented treadmill at three speeds (100%, 120%, and 80% self-selected speed). Bilateral vertical and posterior-anterior GRFs were recorded at each speed. GRF asymmetries were calculated by subtracting the uninjured from the injured limb at each percent of stance. Statistical parametric mapping was used to evaluate the effects of speed on GRF asymmetries across stance. We found vertical and posterior GRF asymmetries were exacerbated at faster speeds and reduced at slower speeds in ACL individuals but not controls (p < .05). No differences in anterior GRF asymmetries were observed between speeds in either group (p > .05). Our results suggest increasing walking speed magnifies GRF asymmetries in individuals with ACL reconstruction. Statement of Clinical Significance: Evaluating both preferred and fast walking speeds may aid in characterizing biomechanical asymmetries in individuals with ACL reconstruction which may be valuable in earlier rehabilitative time points when more difficult tasks like hopping and running are not feasible.

Relationship between forward propulsion and foot motion during gait in healthy young adults

The foot contributes to propulsion and postural stability function by changing its morphology during walking through the truss/windlass mechanisms. We quantified the truss mechanism regarding foot stiffness and the windlass mechanism regarding the movement coordination between the foot arch and metatarsophalangeal (MTP) joint. We aimed to clarify the relationship of these mechanisms with propulsive force and static foot alignment. Forty-eight healthy young adults participated and walked at a comfortable speed. The ground reaction force (GRF), ankle power, and sagittal plane motion of the foot arch and MTP joint were recorded using a three-dimensional motion analysis system. The vertical GRF and foot arch motion were used to quantify foot stiffness as the truss coefficient, and the foot arch and first MTP joint were used to quantify movement coordination as the windlass coefficient. The Foot Posture Index (FPI) and arch height index (AHI) were used to assess static foot alignment. A canonical correlation analysis was performed using the foot- and gait-related index group, and then a single-correlation analysis was performed. The canonical correlation analysis showed that a composite variable consisting of FPI, AHI, and the truss coefficient was related to the anterior GRF (A-GRF) and ankle power. The truss coefficient was positively correlated with A-GRF and ankle power, whereas the windlass coefficient was positively correlated with ankle power. Therefore, the truss and windlass coefficients can be used as indices to evaluate foot function, suggesting that maintaining foot stiffness and foot arch coordination with the first MTP joint is important for propulsion.

Anterior-posterior ground reaction forces across a range of running speeds in unilateral transfemoral amputees

ABSTRACT As a fundamental motor pattern, the ability to run at a range of constant speeds is a prerequisite for participating in competitive games and recreational sports. However, it remains unclear how unilateral transfemoral amputees modulate anterior and posterior ground reaction force impulses (GRFIs) in order to maintain constant running speeds. The purpose of this study was to investigate anterior and posterior GRFIs across a wide range of constant running speeds in unilateral transfemoral amputees wearing a running-specific prosthesis. Eleven runners with unilateral transfemoral amputation ran on an instrumented treadmill at 5 different speeds (30%, 40%, 50%, 60%, and 70% of the average velocity of their 100-m personal records). Anterior-posterior ground reaction forces (GRFs) were measured at 1000 Hz over 14 consecutive steps. Impulse, magnitude, and duration of anterior and posterior GRFs were compared between the affected and unaffected limbs at each speed. The net anterior-posterior GRFI, reflecting the changes in horizontal running velocity, was consistently positive (propulsion) in the affected limb and negative (braking) in the unaffected limb at all speeds. Regardless of running speed, unilateral transfemoral amputees maintain constant running speeds not over each step, but over 2 consecutive steps (i.e., one stride).

Effects of Varying Plantarflexion Stiffness of Ankle-Foot Orthosis on Achilles Tendon and Propulsion Force During Gait.

An ankle-foot orthosis (AFO) with a plantarflexion resistance function, improves post-stroke gait. An AFO with a plantarflexion resistance function not only affects the first rocker function and the weight acceptance but also the late stance phase. Achilles tendon extension is important for ankle joint function and for forward propulsion during the late stance phase; however, the effect of an AFO with a plantarflexion resistance function on the Achilles tendon is unclear. The purpose of this study was to investigate the effect of plantarflexion resistance on the extension of the Achilles tendon and the forward-propulsive force. Herein, 10 healthy adult males participated who walked under three different conditions: a no-AFO condition and two AFO conditions that had different levels of plantarflexion resistance (P1 and P2). The stiffness value of the P1 and P2 conditions was 0.56 and 1.47 Nm/°, respectively. A three-dimensional (3D) motion analysis system and a musculoskeletal model were used to assess the tendon-length change, the ground reaction force, kinematics, and kinetics data. The change in Achilles tendon length was significantly lower in the P1 and P2 conditions than the no-AFO condition. Furthermore, changes in the length of the Achilles tendon significantly decreased in the P2 condition when compared with that in the P1 condition. The peak anterior ground reaction force was significantly lower in the P2 condition than the no-AFO condition. These results suggest that excessive assist provided by an AFO prevents efficient gait by decreasing both the forward-propulsive force and tendon function.

On the mechanical power output required for human running – Insight from an analytical model

In this paper the dynamics of human running on flat terrain and the required mechanical power output with its dependency on various parameters is investigated. Knowing the required mechanical power output is of relevance due to its relationship with the metabolic power. For example, a better understanding of the dependencies of required mechanical power output on weight, running and wind speed, step frequency, ground contact time etc. is very valuable for the assessment, analysis and optimization of running performance. Therefore, a mathematical model based on very few assumptions is devised. The purpose of the proposed model is to relate running speed and required mechanical power output as an algebraic function of the runner’s mass, height, step rate, ground contact time and wind speed. This is relevant in order to better understand the mechanical energy cost of locomotion, and how much it depends on which parameters. The first of the main energy dissipation mechanisms is due to vertical oscillation, i.e., during each step some of the potential energy difference gets transformed into heat. The second mechanism is due to the anterior ground reaction force during the first part of stance and the third is due to aerodynamic drag. With the approximations of constant running speed and a sinusoidal vertical ground reaction force profile one obtains closed algebraic expressions for the center of mass trajectory and the required mechanical power output. Comparisons of model predictions and reported performance data suggest that approximately a quarter of the ground impact energy is stored during the first part of ground contact and then released during the remaining stance phase. Further, one can conclude from the model that less mechanical power output is required when running with higher step rates and a higher center of mass. Non intuitive is the result that a shorter ground contact time is beneficial for fast runs, while the opposite holds for slow runs. An important advantage of the devised model compared to others is that it leads to closed algebraic expressions for the center of mass trajectory and mechanical power output, which are functions of measurable quantities, i.e., of step rate, ground contact time, running speed, runner’s mass, center of mass height, aerodynamic drag at some given speed, wind speed and heart rate. Moreover, the model relies on very few assumptions, which have been verified, and the only tuning parameter is the ratio of recovered elastic energy.

Influence Of Resistance Training On Strength And Gait Kinetics In Individuals With Acl Reconstruction

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) demonstrate reduced hip and knee extensor strength in their injured limb. Previous research suggests strength imbalances reduce an individuals’ ability to propel themselves forward during gait as indicated by the impulse of the anterior ground reaction force (propulsive force; pGRF). As resistance training increases muscular strength, it may improve any propulsion deficits. Therefore, the purpose of this study was to compare hip and knee extensor strength as well as pGRF characteristics between individuals with ACLR who resistance train (RT) and ones who do not (NRT). METHODS: Hip and knee extensor strength and gait were measured in 16 individuals (22.4±4.2 yr, 1.7±0.1 m, 73.8±15.1kg) with unilateral ACLR via isokinetic dynamometry and force platforms, respectively. The RT group had individuals who resistance trained according to the American College of Sports Medicine guidelines consistently after completion of physical therapy. The NRT group included individuals who did not resistance train at all. Independent samples T-tests were used to compare peak hip and knee extensor strength (Nm/kg-1), peak pGRF (N/kg-1), and pGRF impulse (N•s/kg-1) between the RT and NRT groups. Bivariate correlations were used to identify if hip and knee extensor strength were related to pGRF and pGRF impulse. RESULTS: The RT group had greater peak knee extensor torque at 60o/sec-1 (KE60) and 180o/sec-1 (KE180) compared to the NRT group. No differences were observed between groups in peak hip torque, pGRF, or pGRF impulse. There was a negative correlation between KE60 and pGRF during walking (r = -0.531, p=0.034). No correlations were found between pGRF impulse and hip or knee torque. CONCLUSION: Results confirm our hypothesis that in ACLR, individuals in the RT group exhibited greater knee extensor torque than the NRT group. Additionally, greater KE60 was related to less pGRF during walking. An exploratory analysis found no differences in walking or running velocities, indicating the RT group accomplishes the same goal with less force. This may demonstrate greater movement efficiency resulting from resistance training above the improvements in strength alone.

Dynamic Between-Leg Differences While Walking in Anterior Cruciate Ligament-Deficient Patients With and Without Medial Meniscal Posterior Horn Tears.

Background:Patients with anterior cruciate ligament–deficient (ACLD) knees with medial meniscal posterior horn tears (MMPHTs) have been reported to demonstrate a combined stiffening and pivot-shift gait pattern compared with healthy controls. Movement asymmetries are implicated in the development and progression of osteoarthritis.Purpose:To investigate the knee kinematics and kinetic asymmetries in ACLD patients with (ACLD + MMPHT group) and without (ACLD group) MMPHTs while walking on level ground.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 15 patients with isolated unilateral ACL ruptures, 10 with unilateral ACL ruptures and MMPHTs, and 22 healthy controls underwent gait testing between January 2014 and December 2016. Between-leg differences (BLDs) in knee kinematics and kinetics were compared among participants in all groups.Results:The ACLD + MMPHT group demonstrated significantly greater BLDs in knee moments in the sagittal plane during the loading response phase than the ACLD and control groups. Compared with the control group, the ACLD and ACLD + MMPHT groups demonstrated significantly greater BLDs in knee angles in the sagittal plane during the midstance and terminal stance phases. Compared with the control group, significantly greater BLDs in knee rotation moments were found throughout the stance phase in both the ACLD and the ACLD + MMPHT groups. BLDs in lateral ground-reaction forces (GRFs) in the ACLD + MMPHT and ACLD groups were both significantly greater than the control group during the loading response phase. BLDs in anterior GRFs in the ACLD + MMPHT and ACLD groups were both significantly greater than the control group during the loading response phase. Only the ACLD + MMPHT group demonstrated greater BLDs in vertical GRFs than the control group during the loading response phase, while no significant differences were observed between the ACLD and control groups.Conclusion:The ACLD + MMPHT group demonstrated significantly more knee flexion moment asymmetries than the ACLD and control groups during the loading response phase. Both the ACLD + MMPHT and the ACLD groups demonstrated significant knee angle and moment asymmetries in the sagittal plane during the terminal stance phase than the control group. Both the ACLD + MMPHT and the ACLD groups demonstrated knee rotation moment asymmetries during the midstance and terminal stance phases compared with the control group. A rehabilitation program for ACLD patients both with and without MMPHTs should take into consideration these asymmetric gait patterns.

Walking speed changes in response to user-driven treadmill control after stroke

The objective of this study was to determine how individuals poststroke respond to user-driven treadmill (UDTM) controlin terms ofwalking speeds, peak anterior ground reaction forces (AGRF), peak posterior ground reaction forces (PGRF), and trailing limb angles (TLA). Twenty individuals with chronic stroke walked overground during a 10-meter walk test to determine their self-selected (SS) speeds before walking on a treadmill in its fixed-speed (FSTM) and UDTM control modes at their SS and fastest comfortable (Fast) speeds. Paired t-tests were used to compare the walking speeds, peak AGRF, peak PGRF, and TLA among test conditions (α = 0.05). Participants selected similar SS (p > 0.05) and faster Fast walking speeds (p < 0.05) with the UDTM control compared to the FSTM control. There were no changes in their peak AGRF or PGRF for either limb or speed between UDTM and FSTM conditions (p > 0.05). Individuals used greater paretic TLA at SS speeds with UDTM control (p < 0.05). There was no difference in the AGRF required at Fast speeds with FSTM and UDTM control even though participants selected faster speeds with UDTM control. In work with young, healthy adults, we found that the treadmill control condition did not affect the amount of forward propulsion needed. Therefore, it is likely that when walking with UDTM control, individuals poststroke adjust their posture to make better use of their forward propulsion. This means they can reach faster walking speeds without increasing their push-off forces. Future work should assess how to most effectively prescribe UDTM control for gait training programs.

Can shank acceleration provide a clinically feasible surrogate for individual limb propulsion during walking?

Aging and many pathologies that affect gait are associated with reduced ankle power output and thus trailing limb propulsion during walking. However, quantifying trailing limb propulsion requires sophisticated measurement equipment at significant expense that fundamentally limits clinical translation for diagnostics or gait rehabilitation. As a component of joint power, our purpose was to determine if shank acceleration estimated via accelerometers during push-off can serve as a clinically feasible surrogate for ankle power output and peak anterior ground reaction forces (GRF) during walking. As hypothesized, we found that young adults modulated walking speed via changes in peak anterior GRF and peak ankle power output that correlated with proportional changes in shank acceleration during push-off, both at the individual subject (R2 ≥ 0.80, p < 0.01) and group average (R2 ≥ 0.74, p < 0.01) levels. In addition, we found that unilateral deficits in trailing limb propulsion induced via a leg bracing elicited unilateral and relatively proportional reductions in peak anterior GRF, peak ankle power, and peak shank acceleration. These unilateral leg bracing effects on peak shank acceleration correlated with those in peak ankle power (braced leg: R2 = 0.43, p = 0.028) but those effects in both peak shank acceleration and peak ankle power were disassociated from those in peak anterior GRF. In conclusion, our findings in young adults provide an early benchmark for the development of affordable and clinically feasible alternatives for assessing and monitoring trailing limb propulsion during walking.

Comparison of gait, functional activities, and patient-reported outcome measures in patients with knee osteoarthritis and healthy adults using 3D motion analysis and activity monitoring: an exploratory case-control analysis.

ObjectiveTo examine functional performance differences using kinematic and kinetic analysis between participants with and without knee osteoarthritis (OA) to determine which outcomes best characterize persons with and without knee OA.MethodsParticipants with unilateral moderate knee OA (Kellgren–Lawrence grades 2 or 3) and controls without knee pain were matched for age, gender, and body mass index. Primary outcomes included temporal parameters, joint rotations and moments, and ground reaction forces assessed via 3D motion capture during walking and ascending/descending stairs. Secondary outcomes included timed functional activities (sit to stand; tying shoelaces), 48 hrs lower limb activity monitoring, and patient-reported outcome measures (Knee Injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, European Quality of Life–5 Dimensions).ResultsEight matched pairs were analyzed. Compared with controls, OA participants exhibited significant reductions in peak frontal hip and sagittal knee moments, and decreased peak anterior ground reaction force with the affected limb while walking. Ascending stairs, OA participants had slower speed, fewer strides per minute, longer cycle and stance times, and increased trunk range of motion (ROM) in assessments of both limbs; longer swing time and reduced ankle ROM in the affected limb; and increased knee frontal ROM in the unaffected limb. Descending stairs, OA participants had fewer strides per minute and decreased trunk transverse ROM in assessments of both limbs; increased knee frontal ROM in the affected limb; and longer strides, shorter stance and cycle times, increased trunk sagittal and decreased knee transverse ROMs in the unaffected limbs vs controls. Compared with controls, OA participants had slower walking cadence (120–130 vs 100–110 steps/min, respectively), took significantly longer on timed functional measures, and had significantly worse scores in patient-reported outcomes.ConclusionSeveral objectives and patient-reported measures examined in this study could potentially be considered as outcomes in pharmacologic or physical therapy OA trials.

Trailing limb angle is a surrogate for propulsive limb forces during walking post-stroke

BackgroundPropulsive deficits following stroke have been attributed to reduced plantarflexion moments and a reduced trailing limb angle. We sought to determine the validity of the trailing limb angle as a surrogate measure of the anterior ground reaction force, as well as to determine the anatomical landmarks for the trailing limb angle that best approximate the orientation of the ground reaction force. MethodsForty-four participants with chronic stroke walked on a treadmill. At peak propulsion, we computed the trailing limb angle, the anterior orientation of the ground reaction force (the gold standard), and the hip extension angle for correlational analyses. Further, we compared the absolute error of the various trailing limb angle computations to determine which landmarks provided the most accurate representation of the anterior angle of the ground reaction force. FindingsFor the paretic and non-paretic limbs, the anterior angle of the ground reaction force was related to all measures of trailing limb angle as well as the peak propulsive force. The hip extension angle, however, was not related to the angle of the ground reaction force. Only the choice of distal landmarks significantly influenced the error between trailing limb angle and the anterior angle of the ground reaction force. InterpretationThese data suggest that measuring the sagittal plane orientation of the entire limb serves as a suitable surrogate for measuring the anterior angle of the ground reaction force. Although greater errors were observed with kinematic measures of orientation, the magnitude of the error is likely within acceptable ranges.

Walking speed changes in response to novel user-driven treadmill control

Implementing user-driven treadmill control in gait training programs for rehabilitation may be an effective means of enhancing motor learning and improving functional performance. This study aimed to determine the effect of a user-driven treadmill control scheme on walking speeds, anterior ground reaction forces (AGRF), and trailing limb angles (TLA) of healthy adults. Twenty-three participants completed a 10-m overground walking task to measure their overground self-selected (SS) walking speeds. Then, they walked at their SS and fastest comfortable walking speeds on an instrumented split-belt treadmill in its fixed speed and user-driven control modes. The user-driven treadmill controller combined inertial-force, gait parameter, and position based control to adjust the treadmill belt speed in real time. Walking speeds, peak AGRF, and TLA were compared among test conditions using paired t-tests (α = 0.05). Participants chose significantly faster SS and fast walking speeds in the user-driven mode than the fixed speed mode (p > 0.05). There was no significant difference between the overground SS walking speed and the SS speed from the user-driven trials (p < 0.05). Changes in AGRF and TLA were caused primarily by changes in walking speed, not the treadmill controller. Our findings show the user-driven treadmill controller allowed participants to select walking speeds faster than their chosen speeds on the fixed speed treadmill and similar to their overground speeds. Since user-driven treadmill walking increases cognitive activity and natural mobility, these results suggest user-driven treadmill control would be a beneficial addition to current gait training programs for rehabilitation.