A comparison of centre of pressure behaviour and ground reaction force magnitudes when individuals walk overground and on an instrumented treadmill

BackgroundInstrumented treadmills facilitate analysis of consecutive strides in ways that typical overground gait data collections cannot. Researchers have quantified differences between joint kinetic measures whilst walking on an instrumented treadmill compared to those walking overground. The reason for such differences has not yet been established.Research QuestionCan we identify the source or sources of these errors by comparing centre of pressure and ground reaction force measurements recorded on a treadmill to those collected overground?MethodsKinematic and kinetic data were recorded while nineteen individuals walked continuously at their self-selected walking speed overground and on a treadmill. Comparisons of the centre of pressure and ground reaction forces were made between the two conditions using 2-tailed paired t-tests and Cohen’s d effect size.ResultsThe results indicated that participants had significantly faster backwards, lateral and medial centre of pressure velocities when walking on a treadmill compared to when they were walking overground. Additionally, participants also had significantly reduced peak propulsive ground reaction forces when walking on a treadmill than walking overground.SignificanceThese results suggest that shear forces caused by the belts sliding over the treadmill force platforms affect the centre of pressure during early stance, and the minimal acceleration of a participant’s centre of mass during treadmill walking results in reduced propulsive force during late stance. Therefore, care should be taken during studies when comparing kinetic gait variables between overground and treadmill walking.     

Cognitive load of walking in people who are blind: Subjective and objective measures for assessment

BackgroundAlthough walking without vision seems to carry a high cognitive cost, few studies have measured the cognitive load involved in this activity in blind people. The aim of this study was to assess the cognitive load of walking in blind people, using gait analysis, a dual task paradigm and a subjective assessment of cognitive load.MethodsIn a quantitative quasi-experimental design, 25 blind adults walked 40 meters. In one trial, participants walked normally (control condition). In another, they walked while performing an auditory simple reaction time task, and in the third trial they walked, performed the simple reaction time task and avoided obstacles. In addition to the simple reaction time task performance, walking speed was recorded, and participants provided a subjective assessment of cognitive load after each trial. Performance of participants aged less than 60 years were compared with those aged over than 60 years.ResultsWalking significantly reduced performance of the simple reaction time task; carrying out the simple reaction time task while walking significantly reduced walking performance and increased the subjective assessment of cognitive load; and simple reaction time task performance decreased and subjective assessment increased when obstacles were present. Few significant age effects were found.SignificanceWalking without vision involves a cognitive load that increases when the environment becomes complex. Each of the three methods used is relevant when assessing the cognitive load involved in walking in blind people, and could be useful in rehabilitation intervention. The results obtained allowed recommendations to be suggested for the design of technological mobility devices.     

Comparison of measurement protocols to estimate preferred walking speed between sites

BackgroundWalking speed influences a variety of typical outcome measures in gait analysis. Many researchers use a participant’s preferred walking speed (PWS) during gait analysis with a goal of trying to capture how a participant would typically walk. However, the best practices for estimating PWS and the impact of laboratory size and walk distance are still unclear.Research questionIs measured PWS consistent across different distances and between two laboratory sites?MethodsParticipants walked overground at a “comfortable speed” for six different conditions with either dynamic (4, 6, 10, and 400 m) or static (4 and 10 m) starts and stops at two different data collection sites. Repeated measures ANOVA with Bonferroni corrections were used to test for differences between conditions and sites.ResultsParticipants walked significantly faster in the 4, 6, and 10 m dynamic conditions than in the 400 m condition. On average, participants walked slower in the static trials than the dynamic trials of the same distance. There was a significant interaction of lab and condition and so results were examined within each lab. Across both labs, we found that the 4 and 10 m dynamic conditions were not different than the 6 m dynamic condition at both sites, while other tests did not provide consistent results at both sites.SignificanceWe recommend researchers use a 6 m distance with acceleration and deceleration zones to reliably test for PWS across different laboratories. Given some of the differences found between conditions that varied by site, we also emphasize the need to report the test environment and methods used to estimate PWS in all future studies so that the methods can be replicated between studies.     

External feedback during walking improves measures of plantar pressure in individuals with chronic ankle instability

BackgroundIndividuals with chronic ankle instability (CAI) commonly present with an altered walking gait which favors the lateral aspect of their foot. Current rehabilitative protocols are unable to address these gait modifications which are potentially hindering improvements in patient-reported outcomes. Protocols for gait retraining are scarce, thus there is a need to develop intervention strategies and instruments to specifically target foot motion to address gait deficits in individuals with CAI.Research QuestionTo determine the ability of a novel laser device providing external visual feedback (ExFB) during real-time to cause alterations in plantar pressure measures in individuals with CAI.MethodsTwenty-six participants with CAI walked on a treadmill while real-time plantar pressure measures were being recorded during a baseline and feedback condition. Baseline trials were compared with ExFB trials within each subject.ResultsThe ExFB condition was able to significantly reduce plantar pressures on the lateral midfoot and forefoot compared to baseline. A statistically significant medial shift in center of pressure trajectory was also observed in the ExFB condition compared to baseline.SignificanceReal-time external feedback provided by a novel laser device has the ability to reduce lateral column plantar pressures during walking in individuals with CAI.     

Temporal and spatial gait parameters in children with Cri du Chat Syndrome under single and dual task conditions

AimTo describe temporal and spatial gait characteristics in individuals with Cri du Chat syndrome (CdCS) and to explore the effects of performing concurrent manual tasks while walking.MethodsThe gait parameters of 14 participants with CdCS (mean age 10.3, range 3–20 years) and 14 age-matched controls (mean age 10.1, range 3–20 years) were collected using the GAITRite^® instrumented walkway. All participants first walked without any concurrent tasks and then performed 2 motor dual task walking conditions (pitcher and tray).ResultsIndividuals with CdCS took more frequent, smaller steps than controls, but, on average, had a comparable gait speed. In addition, there was a significant task by group interaction. Participants decreased gait speed, decreased cadence, decreased step length, and increased% time in double limb support under dual task conditions compared to single task conditions. However, the age-matched controls altered their gait for both manual tasks, and the participants with CdCS only altered their gait for the tray task.InterpretationAlthough individuals with CdCS ambulate with a comparable gait speed to age-matched controls under single task conditions, they did not significantly alter their gait when carrying a pitcher with a cup of water inside, like controls. It is not clear whether or not individuals with CdCS had difficulty attending to task demands or had difficulty modifying their gait.     

Gait on slopes: Differences in temporo-spatial,kinematic and kinetic gait parameters between walking on a ramp and on a treadmill

BackgroundInclined treadmills or static ramp constructions can be used to investigate downhill gait in a standardised laboratory condition. There is a lack of information how the gait patterns are affected when walking on a ramp or an inclined treadmill during uphill and downhill walking.Research questionIs there a difference in temporo-spatial parameters, sagittal ankle, knee and hip joint angle as well as ground reaction force when walking uphill and downhill on a ramp and a treadmill.MethodsUphill and downhill gait of 15 healthy participants was assessed during walking on a treadmill and on a ramp with slope gradients of 12 °, 6 ° and 0 °. Participants were instructed to walk with the same speed on each slope-system. Kinematic and temporo-spatial paramters were collected using a 3D motion capture system (Qualisys, Gothenburgh, Sweden), kinetic data were collected using pressure insoles (loadsol®, Novel, Germany). Temporo-spatial parameters were analysed using a Friedman ANOVA, time series of kinematic and kinetic data were compared using statistical parametric mapping with a sigificance level of 5%.ResultsOn the treadmill participants walked with significantly shorter steps and shorter contact times, while they significantly increased step frequency compared to walking on a ramp, regardless of slope gradient. In uphill conditions, treadmill gait increased hip and knee flexion angles during the stance phase and increased the forward tilt of the thorax during the entire gait cycle. During downhill walking a significant decrease in dorsiflexion during initial contact, midstance and the second half of the swing phase was observed. Peak resultant forces remained similar compared to walking on the ramp. These alterations might be due to mechanical and psychological effects.SignificanceKnowledge about these differences is important in future study design and data interpretation from existing literature.     

The reliability of measuring medial gastrocnemius muscle-tendon unit lengths during gait

BackgroundUltrasound imaging combined with 3D motion analysis allows for in-vivo assessment of muscle-tendon unit lengths during gait. The clinical relevance of analysing the medial gastrocnemius (MG) and Achilles muscle-tendon junction (MTJ), MG mid-muscle belly fascicles (FAS) and muscle thickness was shown. However, their reliability error estimations over the gait cycle is unknown.Research questionWhat are the intra- and inter-session errors associated with extracting MG belly, thickness, FAS and tendon lengths using ultrasound during gait in healthy participants?Methods3D gait analysis was carried out in ten healthy adults as they walked on an instrumented treadmill at a comfortable walking speed. An ultrasound probe was secured on the leg and tracked by 3D motion analysis. Images were collected during two walking trials with the probe on the MG muscle-belly to estimate FAS lengths and muscle thickness, and during two trials with the probe on the MTJ to estimate muscle-belly and tendon lengths. A second session was performed after 5 ± 4 days where a different operator placed the ultrasound probe. The standard deviation (SD) of absolute and relative lengths changes during the gait cycle over different trials were calculated per participant. SD values averaged over participants represented intra- and inter-session errors.ResultsFor all assessed variables, the intra-session errors were <2.2 mm, except for the FAS lengths (3.1 mm). The inter-session errors were larger than the intra-session, with the highest values found for the absolute muscle-tendon unit lengths (5.6 mm). Relative length errors were smaller than absolute length errors.SignificanceIntra-session errors, which may reflect natural variability and data processing errors, seem more critical when extracting absolute FAS than muscle-tendon lengths. Standardized probe positioning on the MTJ between sessions may improve the inter-session reliability. Expressing the lengths relative to their lengths as the beginning of the gait cycle reduces the inter-session errors.     

The effects of metronome frequency differentially affects gait on a treadmill and overground in people with Parkinson disease

BackgroundTreadmills and rhythmic auditory cueing can influence stepping rhythm for individuals with Parkinson disease (PD). Of concern, however, is that auditory cueing directly addresses the temporal features of gait, whereas adjusting step length may be more important for people with PD. Stepping to a faster cadence when walking overground may increase gait speed, but without requiring an increased step length. Furthermore, given the potentially valuable role of walking on a treadmill for individuals with PD, we are concerned that increasing cadence with rhythmic auditory cueing while walking at a constant treadmill speed will induce even shorter steps.Research questionWhat is the effect of different metronome cue frequencies on spatiotemporal gait parameters when walking overground compared to walking on a treadmill in people with PD?MethodsUsing a repeated-measures design, 21 people with PD (stage 1–3) walked overground and on a treadmill with and without metronome cues of 85 %, 100 %, and 115 % of their baseline cadence frequency for one minute each. We assessed step length, and cadence during all conditions. Gait speed was assessed during overground gait.ResultsAn interaction effect between cue frequency and walking environment revealed that participants took longer steps during the 85 % condition on the treadmill only. When walking overground, metronome cues of 85 % and 115 % of baseline cadence yielded decreases and increases, respectively, in both cadence and gait speed with no associated change in step length.SignificanceThese data suggest that people with PD are able to alter spatiotemporal gait parameters immediately when provided the appropriate metronome cue and walking environment. We propose to target shortened step lengths by stepping to the beat of slow frequency auditory cues while walking on a treadmill, whereas the use of fast frequency cues during overground walking can facilitate faster walking speeds.     

Words matter: instructions dictate “self-selected” walking speed in young adults

BackgroundVariability in gait speed is influenced by age and health status. However, no study has investigated the effects of different instructions on gait speed.Research questionThis study investigated how walking prompts contributed to variability in gait speed.MethodsParticipants walked on a pressurized walkway. Gait speed variability was assessed using multilevel modeling.Results61% of the variance in gait speed was due to instruction, while 14% was due to individual differences.SignificanceReference values for gait speed across a number of prompts will be highly useful for assessing gait performance in young adults. Further, the instruction given produces a large amount of variability in selected walking speed. This finding urges researchers to maintain consistency when delivering walking instructions.     

Slowing down to preserve balance in the presence of optical flow perturbations

BackgroundThe use of sensory and mechanical perturbations applied during walking has grown in popularity due to their ability to elicit instability relevant to falls. However, the vast majority of perturbation studies on walking balance are performed on a treadmill at a fixed speed.Research questionThe aim of this study was to quantify the effects of mediolateral optical flow perturbations on walking speed and balance outcomes in young adults walking with fixed-speed and self-paced treadmill controllers.MethodsFifteen healthy young adults (8 female, age: 23.1 ± 4.6 yrs) completed four five-minute randomized walking trials in a speed-matched virtual reality hallway. In two of the trials, we added continuous mediolateral optical flow perturbations to the virtual hallway. Trials with and without optical flow perturbations were performed with either a fixed-speed or self-paced treadmill controller. We measured walking speed, balance outcomes (step width, margin of stability, local dynamic instability) and gait variability (step width variability and margin of stability variability).ResultsWe found significant increases in step width (+20%, p = 0.004) and local dynamic instability (+11%, p = 0.008) of participants while responding to optical flow perturbations at a fixed treadmill speed. We found no significant differences in these outcome measures when perturbations were applied on a self-paced treadmill. Instead, participants walked 5.7% slower between the self-paced treadmill controller conditions when responding to optical flow perturbations (1.48 ± 0.13 m/s vs. 1.57 ± 0.16 m/s, p = 0.005).SignificanceOur findings suggest that during walking, when presented with a balance challenge, an individual will instinctively reduce their walking speed in order to better preserve stability. However, comparisons to prior literature suggest that this response may depend on environmental and/or perturbation context. Cumulatively, our results point to opportunities for leveraging self-paced treadmill controllers as a more ecologically-relevant option in balance research with potential clinical applications in diagnostics and rehabilitation.     

Immediate effects of treadmill walking in individuals with Lewy body dementia and Huntington’s disease

BackgroundTreadmill training may improve gait disorders associated with neurodegenerative diseases. In Parkinson’s disease (PD), treadmill training alters gait patterns after one session, and long-term training improves gait parameters, fall risk, and quality of life.Research questionWhat is the feasibility and safety of using this intervention for people with Lewy body dementia (LBD) or Huntington’s disease (HD)?MethodsIn this observational study, 10 individuals with HD, 8 individuals with LBD, and 10 control individuals walked for 20 min on a treadmill using a speed dependent protocol starting at a slow comfortable speed and increasing incrementally toward their normal overground speed. Feasibility was determined by compliance to protocol and safety by no incidents of abnormal vital signs or expressions of distress. Changes in gait measures, Timed Up and Go (TUG) scores and quantitative motor function measures (Q-Motor; precision grasp force variability, finger and foot tapping frequency) before and after treadmill walking were analyzed using linear models.ResultsTreadmill training is feasible and safe in LBD and HD; although, participants could not initiate treadmill walking at their comfortable overground speeds, and only 3 participants with HD were able to achieve their overground walking speed within the 20-minute session. No changes in gait measures, TUG times, and Q-Motor measures were found among LBD and HD participants after treadmill walking, although control participants demonstrated significant increases in several gait measures, and foot tap frequency (estimated difference = 0.290; p = 0.026).SignificanceLonger and more frequent treadmill sessions may be needed to see gait and motor function effects in LBD and HD. Motor and cognitive impairments associated with these diseases may make them less amenable to the effects of treadmill training.     

Non-Powered automatic velocity-controlled wheeled walker improves gait and satisfaction in patients with hip fracture when walking downhill: A cross-over study

BackgroundA standard four-wheeled walker is commonly used after surgery for hip fracture to aid ambulation. However, elderly patients experience some difficulties and are at risk for falls; therefore, attempts are being made to address these issues.Research questionDoes the non-powered automatic velocity-controlled (NPAVEC) wheeled walker improves the gait and satisfaction of patients with hip fractures when walking downhill using it?MethodsIn this cross-over study, 21 participants performed three trials of walking downhill with two walkers (an NPAVEC wheeled walker and a standard four-wheeled walker) at a self-selected speed. We compared the lower limb surface electromyography data and self-reported satisfaction scores for both walkers.ResultsRegarding the affected limb, the NPAVEC wheeled walker increased contraction in the vastus medialis (p = 0.003) and tibialis anterior (p = 0.014), and biceps femoris of the unaffected limb (p = 0.01). Additionally, participants reported greater satisfaction when using the NPAVEC wheeled walker (p < 0.001).SignificanceAn NPAVEC wheeled walker, compared to a four-wheeled walker, can assist patients recovering from hip fracture when walking downhill by improving the gait and increasing satisfaction.     

Normative Achilles and patellar tendon shear wave speeds and loading patterns during walking in typically developing children

BackgroundMotion analysis is commonly used to evaluate joint kinetics in children with cerebral palsy who exhibit gait disorders. However, one cannot readily infer muscle-tendon forces from joint kinetics. This study investigates the use of shear wave tensiometry to characterize Achilles and patellar tendon forces during gait.Research QuestionHow do Achilles and patellar tendon wave speed and loading modulate with walking speed in typically developing children?MethodsTwelve typically developing children (9–16 years old) walked on an instrumented treadmill with shear wave tensiometers over their Achilles (n = 11) and patellar (n = 9) tendons. Wave speeds were recorded at five leg length-normalized walking speeds (very slow to very fast). Achilles and patellar tendon moment arms were measured with synchronized ultrasound and motion capture. The tendon wave speed-load relationship was calibrated at the typical walking speed and used to estimate tendon loading at other walking speeds.ResultsCharacteristic Achilles and patellar tendon wave speed trajectories exhibited two peaks over a gait cycle. Peak Achilles tendon force closely aligned with peak ankle plantarflexor moment during pushoff, though force exhibited less modulation with walking speed. A second peak in late swing Achilles loading, which was not evident from the ankle moment, increased significantly with walking speed (p < 0.001). The two peaks in patellar tendon loading occurred at 12 ± 1% and 68 ± 6% of the gait cycle, matching the timing of peak knee extension moment in early stance and early swing. Both patellar tendon load peaks increased significantly with walking speed (p < 0.05).SignificanceThis is the first study to use shear wave tensiometry to characterize Achilles and patellar tendon loading during gait in children. These data could serve as a normative comparison when using tensiometry to identify abnormal tendon loading patterns in individuals who exhibit equinus and/or crouch gait.     

Effects of functional power training on gait kinematics in children with cerebral palsy

BackgroundMuscle weakness is one of the most prevalent symptoms in children with cerebral palsy (CP). Although recent studies show that functional power training can improve strength and functional capacity in young children with CP, effects on specific gait parameters have not previously been reported.Research questionWhat are the effects of functional power training on gait in children with CP? Specifically, we investigated effects of training on gait kinematics and spatiotemporal parameters, and whether these were dependent on walking speed.MethodsTen children with CP (age 5–10 years, GMFCS I–II) participated in a functional power training program. At the start and end of the program, children underwent 3D gait analysis on a treadmill at a gradual range of walking speeds (70–175% of their comfortable walking speed). Multilevel (linear mixed model) analysis was used to evaluate effects pre-post training at different walking velocities.ResultsAlthough children’s self-chosen comfortable walking speed improved (0.71 ± 0.25 to 0.85 ± 0.25 m/s, p < .05), effects on gait kinematics at similar speed were limited and only exceeded statistical and clinically meaningful thresholds when children walked at higher walking speed. At fast speeds, improvements up to 5° were found in knee and hip extension during stance (p < .01).SignificanceThis study demonstrates that gait kinematics can improve after functional power training, but the magnitude of effects is dependent on walking speed. In this light, improvements are underestimated when evaluating gait at pre-training comfortable walking speed only.     

Overground versus treadmill walking in Parkinson’s disease: Relationship between speed and spatiotemporal gait metrics

BackgroundTreadmills provide a safe and convenient way to study the gait of people with Parkinson’s disease (PD), but outcome measures derived from treadmill gait may differ from overground walking.ObjectiveTo investigate how the relationships between gait metrics and walking speed vary between overground and treadmill walking in people with PD and healthy controls.MethodsWe compared 29 healthy controls to 27 people with PD in the OFF-medication state. Subjects first walked overground on an instrumented gait walkway, then on an instrumented treadmill at 85%, 100% and 115% of their overground walking speed. Average stride length and cadence were computed for each subject in both overground and treadmill walking.ResultsStride length and cadence both differed between overground and treadmill walking. Regressions of stride length and cadence on gait speed showed a log-log relationship for both overground and treadmill gait in both PD and control groups. The difference between the PD and control groups during overground gait was maintained for treadmill gait, not only when treadmill speed matched overground speed, but also with ± 15% variation in treadmill speed from that value.SignificanceThese results show that the impact of PD on stride length and cadence and their relationship to gait speed is preserved in treadmill as compared to overground walking. We conclude that a treadmill protocol is suitable for laboratory use in studies of PD gait therapeutics.     

Adaptive gait responses to awareness of an impending slip during treadmill walking

The awareness of potential slip risk has been shown to cause protective changes to human gait during overground walking. It remains unknown if such adaptations to walking pattern also exist when ambulating on a treadmill. This study sought to determine whether and to what extent individuals, when being aware of a potential slip risk during treadmill walking, could adjust their gait pattern to improve their dynamic stability against backward balance loss in response to the impending slip hazard. Fifty-four healthy young subjects (age: 23.9 ± 4.7 years) participated in this study. Subjects’ gait pattern was measured under two conditions: walking on a treadmill without (or normal walking) and with (or aware walking) the awareness of the potential slip perturbation. During both walking conditions, subjects’ full body kinematics were gathered by using a motion capture system. Spatial gait parameters and the dynamic gait stability against backward balance were compared between the two walking conditions. The results revealed that subjects proactively adopted a “cautious gait” during aware walking compared with the normal walking. The cautious gait, which was achieved by taking a shorter step and a more flatfoot landing, positioned the body center of mass closer to the base of support, improving participants’ dynamic stability and increasing their resistance against a possible slip-related fall. The finding from this study could provide insights into the dynamic stability control when individuals anticipate potential slip risk during treadmill walking.     

Influence of non-immersive avatar-based gamification on the Hawthorne Effect in pediatric gait

BackgroundThe Hawthorne Effect occurs when participants alter their behavior when they are aware that they are being examined. The effect has been reported in many experiments, including gait analysis, and is considered an important source of bias that might impact both clinical and research results. Cognitive distraction is one potential solution to reducing the Hawthorne effect during gait analysis, but it is challenging in children, and can, in itself, alter gait. This study investigated the carryover effect of an alternative low-immersion avatar-based intervention on gait and subjective feelings in typically developing children.Research QuestionWill a low-immersion avatar-based intervention change feelings and indicators of temporospatial and kinematic outcomes in children in a laboratory setting, potentially reducing the Hawthorne Effect?MethodsTypically developing children aged 5–13 participated in a standard laboratory gait analysis before experiencing a game in which they viewed their motion on monitors around the lab as that of a cartoon avatar in a 3D virtual environment. Following this intervention, standard walking trials were repeated. In addition, participants completed a survey of their feelings about the study both before onset and after completion.ResultsThirty-one children participated in the study, 16 females and 15 males, mean aged 9.1 years. Arm swing, proposed as a measure of how relaxed and natural gait was, increased significantly following the intervention, while temporospatial parameters did not. The effect was more pronounced in females and younger children. Participants felt significantly happier, more excited, less scared, and less sad after the intervention. Changes in feelings were not closely associated with changes in gait.SignificanceThis study suggests that gamification may reduce the Hawthorne effect and potentially produce more natural gait in children. The game intervention had a carryover effect, producing changes in gait even after the intervention was removed.     

Visual scanning behavior during distracted walking in healthy young adults

BackgroundAn epidemic of pedestrian accidents when walking while texting suggests that people are less aware of their surroundings during distracted walking, and highlights the importance of visual scanning for pedestrian safety. Quantitative examination of visual scanning during distracted walking is still lacking.Research questionIs visual scanning behavior altered by distracted walking in healthy young adults?MethodsWe compared visual scanning behavior in 20 young adults during usual (single-task) walking, walking while performing a letter-fluency task, and walking while texting. Visual scanning behavior was measured by fixation count and dwell time percentage in specific areas of interest. Dual-task effects on gait speed, letter fluency, texting speed and accuracy, and situational awareness were also examined.ResultVisual scanning behavior differed between the three walking conditions. During dual-task letter fluency, participants had significantly more non-walking path fixations than either of the other two conditions (i.e., more frequent, broader visual scanning). Conversely, during dual-task texting, gaze was focused predominantly on the phone, with little visual scanning of the walking path and surrounding environment. When walking without texting or talking, gaze was directed equally to far walking path and surrounding environment.SignificanceTexting while walking is associated with a considerable reduction in overt visual attention to the walking path and surrounding areas. Whether this translates to reduced conscious awareness of environmental stimuli remains unclear. Performing a verbal task while walking was associated with more frequent, wider visual scanning behavior, which may be specific to the nature of the verbal task in this study.     

How to compare knee kinetics at different walking speeds?

BackgroundWalking speed is a confounding factor in biomechanical analyses of gait, but still many studies compare gait biomechanics at comfortable walking speed (CWS) that is likely to differ between groups or conditions. To identify gait deviation unrelated to walking speed, methods are needed to correct biomechanical data over the gait cycle for walking speed.Research questionHow to compare knee kinetics over the gait cycle at different walking speeds?Methods22 asymptomatic subjects walked on a dual-belt treadmill at CWS and 4 fixed speeds. Knee moments in sagittal (KFM) and frontal plane (KAM) were calculated via inverse dynamics. The net moment differences between CWS and fixed speed were expressed as a root-mean-square error (RMSE) normalized to the range of the variable. Two methods to correct for walking speed were compared. In method 1, KFM and KAM values were estimated based on interpolation between speeds at each percentage of the gait cycle. In method 2, principal component analysis was used to extract speed related features to reconstruct KFM and KAM at the speed of interest. The accuracy of both methods was tested using a leave-one-out cross validation.ResultsWalking speed influenced the magnitude and shape of KFM and KAM. To account for these speed influences using both methods, leave-one-out cross validation showed low normalized RMSE (< 5 %), with little difference between the two methods. RMSE for both reconstruction methods were up to 60 % lower than the RMSE between CWS and fixed speed.SignificanceBoth methods could accurately correct knee kinetics over the gait cycle for the effects of walking speed. Walking speed dependency should be incorporated in each gait laboratory’s reference dataset to be able to identify gait deviations unrelated to gait speed.     

The associations between asymmetries in quadriceps strength and gait in individuals with unilateral transtibial amputation

BackgroundIndividuals with unilateral transtibial amputations (ITTAs) are asymmetrical in quadriceps strength. It is unknown if this is associated with gait performance characteristics such as walking speed and limb symmetry.Research questionAre quadriceps strength asymmetries related to walking speed and/ or gait asymmetries in ITTAs?MethodsKnee-extensor isometric maximum voluntary torque (MVT) and rate of torque development (RTD) were measured in eight ITTAs. Gait data were captured as the ITTAs walked at self-selected habitual and fast speeds. Step length and single support time, peak knee extension moments and their impulse and peak vertical ground reaction force (vGRF) in the braking and propulsive phases of stance were extracted. Bilateral Asymmetry Index (BAI) and, for gait variables only, difference in BAI between walking speeds (ΔBAI) were calculated. Correlation analyses assessed the relationships between MVT and RTD asymmetry and (1) walking speed; (2) gait asymmetries.ResultsAssociations between strength and gait BAIs generally became more apparent at faster walking speeds, and when the difference in BAI between fast and habitual walking speed was considered. BAI RTD was strongly negatively correlated with habitual and fast walking speeds (r=∼0.83). Larger BAI RTD was strongly correlated with propulsive vGRF BAI in fast walking, and larger ΔBAIs in vGRF during both the braking and propulsion phases of gait (r = 0.74–0.92). ITTAs who exhibited greater BAI MVT showed greater ΔBAI in single support time (r = 0.83).SignificanceWhile MVT and RTD BAI appear to be associated with gait asymmetries in ITTAs, the magnitude of the asymmetry in RTD appears to be a more sensitive marker of walking speed. Based on these results, it’s possible that strengthening the knee-extensors of the amputated limb to improve both MVT and RTD symmetry may benefit walking speed, and reduce asymmetrical loading in gait.