Biomechanics of overground vs. treadmill walking in healthy individuals

Effect of specific gait modifications on medial knee loading, metabolic cost and perception of task difficulty

BACKGROUND

The metabolic cost and cognitive demand of altering natural gait have not been well studied. The purpose of this investigation was to assess three modified patterns - toe out, ipsilateral trunk lean and a medial weight shift at the foot - on the basis of 1) medial knee joint load reduction, 2) metabolic cost of performance and 3) subject perception of task difficulty.

METHODS

12 healthy individuals underwent 3 dimensional motion analysis and metabolic testing to assess the gait mechanics and energy expenditure of natural gait and the three experimental gait patterns, performed to a self-selected moderate degree. Walking speed was controlled. Perceived workload was assessed using the NASA Task Load Index.

FINDINGS

Trunk lean significantly reduced first peak knee adduction moment (↓32%, P<0.001) as well as KAM impulse (↓35%, P<0.001), but was costly in terms of energy expenditure (↑11%, P<0.001) and perceived workload (↑1178%, P<0.001). A moderate toe-out pattern significantly reduced the second peak knee adduction moment (↓32%, P<0.001) and KAM impulse (↓14%, P=0.026), but had no effect on the first peak. Conversely, toe-out was least demanding in terms of additional energy expenditure (↑2%, P=0.001) and perceived workload (↑314%, P=0.001). Medial shift did not reduce knee adduction moment.

INTERPRETATION

The prioritization of joint load reduction versus additional metabolic and cognitive demands could play a substantial role in the clinical decision making process of selecting a modified gait pattern.

Treadmill versus overground and barefoot versus shod comparisons of triceps surae fascicle behaviour in human walking and running

Studies of human locomotion are commonly performed on a treadmill or overground, as well as with or without footwear. These testing modalities have been suggested to influence kinematics, kinetics and/or spatio-temporal variables differently. However, it is unclear whether they influence contractile behaviour at the level of the muscle fascicles. This has major relevance because results from studies performed with different combinations of the testing modalities are often compared. The present study used ultrasound to examine fascicle behaviour of the medial gastrocnemius (MG) and soleus muscles of ten young, healthy males during walking and running on a treadmill and overground, as well as barefoot and shod. Barefoot conditions resulted in modestly shorter step durations than corresponding shod conditions, whereas no consistent temporal differences were observed between overground and treadmill locomotion. For both comparisons, no differences were observed in soleus or MG fascicle behaviour between corresponding conditions in walking or running, although soleus consistently exhibited smaller, lower velocity length changes than MG. It is concluded that the examined testing modalities are equally valid for studying muscle fascicle behaviour during locomotion. This conclusion is supported by a comparison of our data to the results of 16 previous studies that used various combinations of testing modalities; muscle fascicle behaviour is qualitatively similar between studies for a given muscle and gait.

The influence of gait speed on co-activation in unilateral spastic cerebral palsy children

BACKGROUND

Physiological co-activation of antagonistic muscles during gait allows stability of loaded joints. Excessive co-activation restrains motion and increases energy expenditure. Co-activation is increased by gait speed and in the case of upper motor neuron lesions. This study aimed to assess the pathological component of co-activation in children with unilateral cerebral palsy.

METHODS

10 children with unilateral cerebral palsy and 10 typically developing children walked at spontaneous, slow and fast speeds. The spatio-temporal parameters and electromyographic activity of the rectus femoris, vastus medialis, semi-tendinosus, tibialis anterior and soleus of both lower limbs were recorded. A co-activation index was computed from the EMG envelopes. A mixed linear model was used to assess the effect of walking speed on the index of the antagonistic muscle couples (rectus femoris/semi-tendinosus, vastus medialis/semi-tendinosus and tibialis anterior/soleus) in the different limbs.

FINDINGS

A greater effect of walking speed on co-activation was found in the involved limbs of children with cerebral palsy for all muscle couples, compared with their uninvolved limbs and the limbs of typically developing children. In typically developing children, but not in children with cerebral palsy, the effect of gait speed on the co-activation index was lower in the rectus femoris/semi-tendinosus than in the other agonist/antagonist muscle couples.

INTERPRETATIONS

In children with cerebral palsy, a pathological component of muscle activation might be responsible for the greater increase in co-activation with gait speed in the involved limb. Altered motor control could explain why the co-activation in the rectus femoris/semi-tendinosus couple becomes more sensitive to speed.

Characteristic activities of lower limbs with body weight support ratio

In this study, we investigated a lower limbs muscle activity during body weight support treadmill training (BWSTT). Informed consent was obtained from 16 healthy men. Experimental system consists of force plate, treadmill, three-dimensional motion analysis system, electromyograph, and body weight support device. Body weight support (BWS) was set every 15% increase from 0% to 45%. Walking speed was 4.17 km/h. The measurement data were reaction forces, joint angles, joint moments and lower limbs muscle activities. The vertical reaction force shows two peaks. Two peaks decreased with increase of BWS together. Joint angles did not show significant changes with BWS. However, only the extension of hip angle was decreased with BWS. The peaks of joint moment were decreased. Decrease of ankle joint moment was greatest compared with other moment. Decrease of peaks of muscle activity by BWS was observed during stance phase, and did not almost change during swing phase.

The functional role of the triceps surae muscle during human locomotion

Aim

Despite numerous studies addressing the issue, it remains unclear whether the triceps surae muscle group generates forward propulsive force during gait, commonly identified as ‘push-off’. In order to challenge the push-off postulate, one must probe the effect of varying the propulsive force while annulling the effect of the progression velocity. This can be obtained by adding a load to the subject while maintaining the same progression velocity.

Methods

Ten healthy subjects initiated gait in both unloaded and loaded conditions (about 30% of body weight attached at abdominal level), for two walking velocities, spontaneous and fast. Ground reaction force and EMG activity of soleus and gastrocnemius medialis and lateralis muscles of the stance leg were recorded. Centre of mass velocity and position, centre of pressure position, and disequilibrium torque were calculated.

Results

At spontaneous velocity, adding the load increased disequilibrium torque and propulsive force. However, load had no effect on the vertical braking force or amplitude of triceps activity. At fast progression velocity, disequilibrium torque, vertical braking force and triceps EMG increased with respect to spontaneous velocity. Still, adding the load did not further increase braking force or EMG.

Conclusions

Triceps surae is not responsible for the generation of propulsive force but is merely supporting the body during walking and restraining it from falling. By controlling the disequilibrium torque, however, triceps can affect the propulsive force through the exchange of potential into kinetic energy.

Locomotor adaptation to a soleus EMG-controlled antagonistic exoskeleton

Locomotor adaptation in humans is not well understood. To provide insight into the neural reorganization that occurs following a significant disruption to one's learned neuromuscular map relating a given motor command to its resulting muscular action, we tied the mechanical action of a robotic exoskeleton to the electromyography (EMG) profile of the soleus muscle during walking. The powered exoskeleton produced an ankle dorsiflexion torque proportional to soleus muscle recruitment thus limiting the soleus' plantar flexion torque capability. We hypothesized that neurologically intact subjects would alter muscle activation patterns in response to the antagonistic exoskeleton by decreasing soleus recruitment. Subjects practiced walking with the exoskeleton for two 30-min sessions. The initial response to the perturbation was to "fight" the resistive exoskeleton by increasing soleus activation. By the end of training, subjects had significantly reduced soleus recruitment resulting in a gait pattern with almost no ankle push-off. In addition, there was a trend for subjects to reduce gastrocnemius recruitment in proportion to the soleus even though only the soleus EMG was used to control the exoskeleton. The results from this study demonstrate the ability of the nervous system to recalibrate locomotor output in response to substantial changes in the mechanical output of the soleus muscle and associated sensory feedback. This study provides further evidence that the human locomotor system of intact individuals is highly flexible and able to adapt to achieve effective locomotion in response to a broad range of neuromuscular perturbations.

Biomechanics of spontaneous overground walk-to-run transition

The purpose of the present study is to describe the biomechanics of spontaneous walk-to-run transitions (WRTs) in humans. After minimal instructions, 17 physical active subjects performed WRTs on an instrumented runway enabling measurement of speed, acceleration, spatiotemporal variables, ground reaction forces and 3D kinematics. The present study describes (1) the mechanical energy fluctuations of the body centre-of-mass (BCOM) as a reflection of the whole body dynamics and (2) the joint kinematics and kinetics. Consistent with previous research, the spatiotemporal variables show a sudden switch from walking to running in one transition step. During this step there is a sudden increase in forward speed, the so-called speed jump (0.42 m/s). At total body level, this is reflected in a sudden increase in energy of the BCOM (0.83 ± 0.14 J/kg) and an abrupt change from an out-of-phase to an in-phase organization of the kinetic and potential energy fluctuations. During the transition step a larger net propulsive impulse compared to the preceding and following steps is observed due to a decrease in the braking impulse. It is suggested that the altered landing configuration (prepared during the last 40% of the preceding swing) places the body in an optimal configuration to minimize this braking impulse. We hypothesize this configuration also evokes a reflex allowing a more powerful push off, which generates enough power to complete the transition and launch the first flight phase. This powerful push-off is also reflected in the vertical ground reaction force which suddenly changes to a running pattern.

Maximum walking speeds obtained using treadmill and overground robot system in persons with post-stroke hemiplegia

Background

Previous studies demonstrated that stroke survivors have a limited capacity to increase their walking speeds beyond their self-selected maximum walking speed (SMWS). The purpose of this study was to determine the capacity of stroke survivors to reach faster speeds than their SMWS while walking on a treadmill belt or while being pushed by a robotic system (i.e. “push mode”).

Methods

Eighteen chronic stroke survivors with hemiplegia were involved in the study. We calculated their self-selected comfortable walking speed (SCWS) and SMWS overground using a 5-meter walk test (5-MWT). Then, they were exposed to walking at increased speeds, on a treadmill and while in “push mode” in an overground robotic device, the KineAssist, until they were tested at a speed that they could not sustain without losing balance. We recorded the time and number of steps during each trial and calculated gait speed, average cadence and average step length.

Results

Maximum walking speed in the “push mode” was 13% higher than the maximum walking speed on the treadmill and both were higher (“push mode”: 61%; treadmill: 40%) than the maximum walking speed overground. Subjects achieved these faster speeds by initially increasing both step length and cadence and, once individuals stopped increasing their step length, by only increasing cadence.

Conclusions

With post-stroke hemiplegia, individuals are able to walk at faster speeds than their SMWS overground, when provided with a safe environment that provides external forces that requires them to attempt dynamic stability maintenance at higher gait speeds. Therefore, this study suggests the possibility that, given the appropriate conditions, people post-stroke can be trained at higher speeds than previously attempted.

Gait phase detection and discrimination between walking-jogging activities using hidden Markov models applied to foot motion data from a gyroscope

In this paper we present a classifier based on a hidden Markov model (HMM) that was applied to a gait treadmill dataset for gait phase detection and walking/jogging discrimination. The gait events foot strike, foot flat, heel off, toe off were detected using a uni-axial gyroscope that measured the foot instep angular velocity in the sagittal plane. Walking/jogging activities were discriminated by processing gyroscope data from each detected stride. Supervised learning of the classifier was undertaken using reference data from an optical motion analysis system. Remarkably good generalization properties were achieved across tested subjects and gait speeds. Sensitivity and specificity of gait phase detection exceeded 94% and 98%, respectively, with timing errors that were less than 20 ms, on average; the accuracy of walking/jogging discrimination was approximately 99%.

A novel walking speed estimation scheme and its application to treadmill control for gait rehabilitation

Background

Virtual reality (VR) technology along with treadmill training (TT) can effectively provide goal-oriented practice and promote improved motor learning in patients with neurological disorders. Moreover, the VR + TT scheme may enhance cognitive engagement for more effective gait rehabilitation and greater transfer to over ground walking. For this purpose, we developed an individualized treadmill controller with a novel speed estimation scheme using swing foot velocity, which can enable user-driven treadmill walking (UDW) to more closely simulate over ground walking (OGW) during treadmill training. OGW involves a cyclic acceleration-deceleration profile of pelvic velocity that contrasts with typical treadmill-driven walking (TDW), which constrains a person to walk at a preset constant speed. In this study, we investigated the effects of the proposed speed adaptation controller by analyzing the gait kinematics of UDW and TDW, which were compared to those of OGW at three pre-determined velocities.

Methods

Ten healthy subjects were asked to walk in each mode (TDW, UDW, and OGW) at three pre-determined speeds (0.5 m/s, 1.0 m/s, and 1.5 m/s) with real time feedback provided through visual displays. Temporal-spatial gait data and 3D pelvic kinematics were analyzed and comparisons were made between UDW on a treadmill, TDW, and OGW.

Results

The observed step length, cadence, and walk ratio defined as the ratio of stride length to cadence were not significantly different between UDW and TDW. Additionally, the average magnitude of pelvic acceleration peak values along the anterior-posterior direction for each step and the associated standard deviations (variability) were not significantly different between the two modalities. The differences between OGW and UDW and TDW were mainly in swing time and cadence, as have been reported previously. Also, step lengths between OGW and TDW were different for 0.5 m/s and 1.5 m/s gait velocities, and walk ratio between OGS and UDW was different for 1.0 m/s gait velocities.

Conclusions

Our treadmill control scheme implements similar gait biomechanics of TDW, which has been used for repetitive gait training in a small and constrained space as well as controlled and safe environments. These results reveal that users can walk as stably during UDW as TDW and employ similar strategies to maintain walking speed in both UDW and TDW. Furthermore, since UDW can allow a user to actively participate in the virtual reality (VR) applications with variable walking velocity, it can induce more cognitive activities during the training with VR, which may enhance motor learning effects.

Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

BACKGROUND

Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user's nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking.

METHODS

We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step inter-subject variability of these profiles by calculating variance-to-signal ratios.

RESULTS

We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects.

CONCLUSION

Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee's nervous system.

A self-adaptive foot-drop corrector using functional electrical stimulation (FES) modulated by tibialis anterior electromyography (EMG) dataset

We developed a functional electrical stimulator for correcting the gait patterns of patients with foot-drop problem. The stimulating electrical pulses of the system are modulated to evoke contractions of the tibialis anterior muscle, by emulating the normal patterns. The modulation is adaptive, i.e. the system can predict the user's step frequency and the generated stimulation can match each step in real-time. In this study, step data from 11 young healthy volunteers were acquired, and five prediction algorithms were evaluated by the acquired data, including the average of Previous N steps (P-N), the Previous Nth step (P-Nth), General Regression Neural Network (GRNN), Autoregressive (AR) and Kalman filter (KF). The algorithm with the best efficiency-accuracy trade-off (P-N, when N=5) was implemented in the FES system. System evaluation results obtained from a post-stroke patient with foot-drop showed that the system of this study demonstrated better performance on gait pattern correction than the methods widely adopted in commercial products.

Unmatched perception of speed when running overground and on a treadmill

This study compared the perception of speed between overground and treadmill running. Twenty-one participants ran overground around an athletic track at their preferred speed for 3 min, immediately followed by a 3-min treadmill run and a further 3-min overground run. During the treadmill run, participants were blinded to the speed display and were free to adjust the speed until it was perceived similar as their previous self-selected overground speed. A video camera was used to determine the average running speed during each overground run. A one-way ANOVA with repeated measures was used to detect differences among the three speeds: overground speed during session 1 (OG1), perceived overground speed on the treadmill (TM), and overground speed during session 2 (OG2). A significant difference among the three running speeds was found (P=.039). Post hoc analyses showed that the treadmill speed was much slower than both overground speeds but the overground speed did not differ between session 1 and session 2 (OG1: 3.99 (0.78) m/s, TM: 2.73 (0.62) m/s, OG2: 3.80 (0.74) m/s). These findings confirmed that one's perception of speed was influenced by the treadmill on which individuals were unable to match their corresponding self-selected overground running speed. The unmatched perception of speed is likely due to the distortion of normal visual inputs resulting from the discrepancy between observed and expected optic flow. Clinicians, therapists and treadmill users should be aware of the different psychological demands between treadmill and overground locomotion when selecting gait speed.

Similar muscles contribute to horizontal and vertical acceleration of center of mass in forward and backward walking: implications for neural control

Leg kinematics during backward walking (BW) are very similar to the time-reversed kinematics during forward walking (FW). This suggests that the underlying muscle activation pattern could originate from a simple time reversal, as well. Experimental electromyography studies have confirmed that this is the case for some muscles. Furthermore, it has been hypothesized that muscles showing a time reversal should also exhibit a reversal in function [from accelerating the body center of mass (COM) to decelerating]. However, this has not yet been verified in simulation studies. In the present study, forward simulations were used to study the effects of muscles on the acceleration of COM in FW and BW. We found that a reversal in function was indeed present in the muscle control of the horizontal movement of COM (e.g., tibialis anterior and gastrocnemius). In contrast, muscles' antigravity contributions maintained their function for both directions of movement. An important outcome of the present study is therefore that similar muscles can be used to achieve opposite functional demands at the level of control of the COM when walking direction is reversed. However, some muscles showed direction-specific contributions (i.e., dorsiflexors). We concluded that the changes in muscle contributions imply that a simple time reversal would be insufficient to produce BW from FW. We therefore propose that BW utilizes extra elements, presumably supraspinal, in addition to a common spinal drive. These additions are needed for propulsion and require a partial reconfiguration of lower level common networks.

Anteroposterior stability of the knee during the stance phase of gait after anterior cruciate ligament deficiency

Quadriceps avoidance and higher flexion strategies have been assumed as effects of ACL deficiency on knee joint function during gait. However, the effect of ACL deficiency on anteroposterior stability of the knee during gait is not well defined. In this study, 10 patients with unilateral acute ACL ruptures and the contralateral side intact performed gait on a treadmill. Flexion angles and anteroposterior translation of the ACL injured and the intact controlateral knees were measured at every 10% of the stance phase of the gait (from heel strike to toe-off) using a combined MRI and dual fluoroscopic imaging system (DFIS). The data indicated that during the stance phase of the gait, the ACL-deficient knees showed higher flexion angles compared to the intact contralateral side, consistent with the assumption of a higher flexion gait strategy. However, the data also revealed that the ACL-deficient knees had higher anterior tibial translation compared to the intact contralateral side during the stance phase of the gait. The higher flexion gait strategy was not shown to correlate to a reduction of the anterior tibial translation in ACL deficient knees. These data may provide indications for conservative treatment or surgical reconstruction of the ACL injured knees in restoration of the knee kinematics during daily walking activities.

Comparison of pelvic complex kinematics during treadmill and overground walking

OBJECTIVES

To determine if there are changes in temporal gait parameters with a focus on pelvis when comparing overground and treadmill ambulation, and to assess the effect of sex.

DESIGN

An observational study employing motion analysis techniques to evaluate pelvic movement during gait.

SETTING

University biomechanics laboratory.

PARTICIPANTS

Men (n=8; 22.5±3.0 y) and women (n=6; 23.8±4.1 y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Cadence, stride time, stance phase percent, and pelvic tilt, obliquity, and rotation parameters throughout the gait cycle were assessed during overground and treadmill walking. Kinematic data were recorded using a passive full body marker based motion analysis system. While an independent sample t test was used to determine if differences in walking speed were evident between sexes, a 2-way, repeated-measures analysis of variance was performed to examine the effect of walking mode and sex on each dependent variable.

RESULTS

Significant differences (P<.05) between overground and treadmill walking for the temporal parameters analyzed were evident for both sexes. A lower pelvic obliquity motion for treadmill walking when compared with overground walking was evident for both sexes, and the pelvic rotation movement pattern showed the greatest difference between walking modes. The majority of the significant differences between sexes were of a magnitude greater than the differences between overground and treadmill walking.

CONCLUSIONS

The differences in temporal and angular kinematics identified in the present study should be considered when treadmills are used in a rehabilitation program.

Walking on High Heels Changes Muscle Activity and the Dynamics of Human Walking Significantly

The aim of the study was to investigate the distribution of net joint moments in the lower extremities during walking on high-heeled shoes compared with barefooted walking at identical speed. Fourteen female subjects walked at 4 km/h across three force platforms while they were filmed by five digital video cameras operating at 50 frames/second. Both barefooted walking and walking on high-heeled shoes (heel height: 9 cm) were recorded. Net joint moments were calculated by 3D inverse dynamics. EMG was recorded from eight leg muscles. The knee extensor moment peak in the first half of the stance phase was doubled when walking on high heels. The knee joint angle showed that high-heeled walking caused the subjects to flex the knee joint significantly more in the first half of the stance phase. In the frontal plane a significant increase was observed in the knee joint abductor moment and the hip joint abductor moment. Several EMG parameters increased significantly when walking on high-heels. The results indicate a large increase in bone-on-bone forces in the knee joint directly caused by the increased knee joint extensor moment during high-heeled walking, which may explain the observed higher incidence of osteoarthritis in the knee joint in women as compared with men.

Modulation of weight off-loading level over body-weight supported locomotion training

With the evolution of robotic systems to facilitate overground walking rehabilitation, it is important to understand the effect of robotic-aided body-weight supported loading on lower limb muscle activity, if we are to optimize neuromotor recovery. To achieve this objective, we have collected and studied electromyography (EMG) data from key muscles in the lower extremity from healthy subjects walking over a wide range of body-weight off-loading levels as provided by a bespoke gait robot. By examining the impact of body-weight off-loading, it was found that muscle activation patterns were sensitive to the level of off-loading. In addition, a large off-loading might introduce disturbance of muscle activation pattern, led to a wider range of motion in terms of dorsiflexion/plantarflexion. Therefore, any future overground training machine should be enhanced to exclude unnecessary effect of body off-loading in securing the sustaining upright posture and providing assist-as-needed BWS over gait rehabilitation.

Investigation of the Treadport for gait rehabilitation of spinal cord injury

The goal of this study is to compare the effect of training by the University of Utah's Treadport versus a conventional treadmill on gait improvement of spinal-cord-injury (SCI) patients. Four incomplete SCI subjects who had reached a rehabilitation plateau were selected to have training first on the treadmill and then the Treadport. Spatiotemporal and gait parameters were utilized to make a comparison between the two training conditions. Overall, the results demonstrated statically significant improvements in most of the spatiotemporal as well as some of the gait parameters during training with the Treadport relative to the traditional treadmill.

Walking speed, unilateral leg loading, and step symmetry in young adults

The purpose of this study was to examine the effects of gait speed and unilateral lower limb loading on step time and step length symmetry in healthy adults. Spatiotemporal gait data were collected from 22 healthy subjects (11 men, 11 women), using the GaitRite walkway, under four randomly sequenced test conditions: self-selected speed (SS), fast speed (F), self-selected speed with the right leg loaded (LSS), and the fastest attainable speed with the right leg loaded (LF). The symmetry index, calculated with the formula [((R-L)/0.5 × (R+L)) × 100], was used to quantify step time and step length symmetry. It was found that over-ground gait speed had no significant effects on the symmetry of step time or step length. Unilateral lower limb loading significantly increased step time asymmetry, with longer step time for the loaded leg. Step symmetry was further compromised and became more asymmetrical when, in addition to unilateral leg loading, subjects maximized their gait speed. This effect of fast speed with unilateral leg loading was particularly prominent in relation to step length, with its shortening in the unloaded leg and lengthening in the loaded leg. These observations in healthy subjects may serve as a reference for the assessment of gait symmetry in patients with unilateral lower limb pathologies.

Comparison between overground and dynamometer manual wheelchair propulsion

Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (R ranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent with the direction and amount of force applied, the time peak force was reached, push angle, and their stroke frequency between conditions.

Ageing and limb dominance effects on foot-ground clearance during treadmill and overground walking

BACKGROUND

Foot-ground clearance during the gait cycle swing phase is a critical locomotor adaptation to uneven terrain and non-optimal lower limb control has been linked to tripping and falling. The aim of this research was to determine ageing effects on bilateral foot-ground clearance during overground and treadmill walking.

METHODS

Ageing and walking surface effects on bilateral foot trajectory control were investigated in 11 older (mean age 73.8 years) and 11 young (mean age 22.5 years) participants. First maximum clearance after toe-off, minimum foot-ground clearance and second maximum clearance prior to heel contact were determined from sampled 3-dimensional marker coordinates during preferred-speed treadmill walking and walking overground.

FINDINGS

Preferred walking speed was lower in treadmill walking for both groups. In both groups non-dominant minimum foot-ground clearance and first maximum clearance were greater than for the dominant foot. A high positive correlation was found between these two swing foot clearances when older adults walked on the treadmill. Second maximum clearance was reduced in the older group but this was the only overall age effect. Treadmill walking reduced minimum foot-ground clearance relative to overground locomotion except in the older adults' non-dominant limb that revealed greater vertical clearance height in the non-dominant foot.

INTERPRETATION

Decreased second maximum clearance in the older group may be linked to reduced dorsiflexion. Greater minimum foot-ground clearance in the older adults' non-dominant foot may reflect functional asymmetry, in which the non-dominant limb primarily secures or stabilizes gait. The high positive correlation between first maximum and minimum foot-ground clearances suggests that intervention designed to increase first maximum clearance may also increase minimum foot-ground clearance. A direction for future research is to further understand ageing effects on lower limb trajectory variables in response to a range of walking surface characteristics.

Does close proximity robot motion tracking alter gait?

Dynamic fluoroscopic imaging and three-dimensional model-image registration techniques provide detailed joint kinematic measurements for motions constrained to small volumes of space. Several groups are working to mount radiographic imaging hardware onto mobile platforms to provide these same imaging capabilities for observation of unrestricted activities. These dynamic radiographic imaging systems could provide accurate skeletal kinematics during a wide range of clinically relevant, daily activities. However, the premise that people move naturally when followed by a dynamic imaging system has not been evaluated. The goal of this study was to determine if a close-up robot tracking system affects natural free-speed gait. 14 healthy adults were recruited to walk through the workspace of a dynamic radiographic imaging system. Randomized walking trials were performed with and without the dynamic imaging system tracking the motions of the subject's left knee. With- and without-robot trials were compared using detailed temporal-spatial and frequency analysis of kinematic and kinetic parameters. On average, participants increase their stride length by 0.9 cm. There also were slight increases in unexplained variation in ankle flexion/extension and ground reaction forces compared to baseline measurements. The statistically significant differences indicate that, on average, people tried to move faster through the workspace of the dynamic radiographic imaging system while it was actively tracking their motion. These differences are small and potentially clinically irrelevant.

A Manipulation of Visual Feedback during Gait Training in Parkinson's Disease

Visual cues are known to improve gait in Parkinson's disease (PD); however, the contribution of optic flow continues to be disputed. This study manipulated transverse line cues during two gait training interventions (6 weeks). PD subjects (N = 42) were assigned to one of three groups: treadmill (TG), overground (OG), or control group (CG). Participants walked across lines placed on either treadmills or 16-meter carpets, respectively. The treadmill (TG) offered a reduced dynamic flow from the environment, while lines presented on the ground (OG) emphasized optic flow related to the participant's own displacement. Both interventions significantly improved (and maintained through retention period) step length, thus improving walking velocity. Only the OG improved in the TUG test, while only the TG showed hints of improving (and maintaining) motor symptoms. Since gait improvements were found in both training groups, we conclude that by reducing optic flow, gait benefits associated with visual cueing training can still be achieved.

Systematic variation of prosthetic foot spring affects center-of-mass mechanics and metabolic cost during walking

Lower-limb amputees expend more energy to walk than non-amputees and have an elevated risk of secondary disabilities. Insufficient push-off by the prosthetic foot may be a contributing factor. We aimed to systematically study the effect of prosthetic foot mechanics on gait, to gain insight into fundamental prosthetic design principles. We varied a single parameter in isolation, the energy-storing spring in a prototype prosthetic foot, the controlled energy storage and return (CESR) foot, and observed the effect on gait. Subjects walked on the CESR foot with three different springs. We performed parallel studies on amputees and on non-amputees wearing prosthetic simulators. In both groups, spring characteristics similarly affected ankle and body center-of-mass (COM) mechanics and metabolic cost. Softer springs led to greater energy storage, energy return, and prosthetic limb COM push-off work. But metabolic energy expenditure was lowest with a spring of intermediate stiffness, suggesting biomechanical disadvantages to the softest spring despite its greater push-off. Disadvantages of the softest spring may include excessive heel displacements and COM collision losses. We also observed some differences in joint kinetics between amputees and non-amputees walking on the prototype foot. During prosthetic push-off, amputees exhibited reduced energy transfer from the prosthesis to the COM along with increased hip work, perhaps due to greater energy dissipation at the knee. Nevertheless, the results indicate that spring compliance can contribute to push-off, but with biomechanical trade-offs that limit the degree to which greater push-off might improve walking economy.

Comparison of motor control deficits during treadmill and overground walking poststroke

BACKGROUND

Force-sensing split-belt treadmills (TMs) provide an alternative to the conventional overground (OG) setting and allow new avenues for analyzing the biomechanics and motor control of walking. However, walking control may differ on a TM compared with walking OG.

OBJECTIVE

To compare spatiotemporal, kinematic, and EMG-based measures of motor control between TM and OG walking at self-selected and fastest comfortable speeds in persons with poststroke hemiparesis.

METHODS

Individuals with chronic hemiparesis (56) and similarly aged healthy individuals (17) walked over an instrumented walkway and on an instrumented split-belt TM; 16 channels of EMG recorded bilateral muscle activity, and a 12-camera motion capture system collected bilateral 3D kinematics. The authors applied a nonnegative matrix factorization (NNMF) algorithm to examine the underlying patterns of motor control.

RESULTS

Self-selected walking patterns differed on the TM versus OG in controls: speed decreased, stride length decreased, stance percentage increased, and double-support percentage increased. Poststroke, responses were similar, but cadence also decreased, and step length asymmetry increased. Kinematic patterns were similar except those associated with slower walking speeds. NNMF demonstrated similar EMG variance in the 2 environments.

CONCLUSION

Persons, both healthy and poststroke, walk with different gait parameters on the TM. Although measures of motor control were mostly similar between the 2 environments, the TM induced step length asymmetry in 30% of participants (60% of whom took longer paretic steps). TM walking, therefore, is a valid method for detecting motor control deficits.

Energy cost of walking in transfemoral amputees: Comparison between Marlo Anatomical Socket and Ischial Containment Socket

OBJECTIVE

To compare energy cost of walking (ECW) and prosthesis-related perceived mobility with the Marlo Anatomical Socket (MAS(®)) and the Ischial Containment (IC) Socket.

METHOD

Transfemoral (TF) amputees were enrolled in the study. ECW tests were conducted inside, in a hallway with a regular floor surface. Subjects had to walk back and forth on a 61m linear course at their own self-selected speed. Metabolic and heart rate data were collected during the walking test using a portable gas analyzer. All measurements were made at steady state (SS). The tests were performed first using the IC socket and then after 30 days of MAS(®) use; the last test was carried out after 60 days of MAS(®) use. The amputees were also administered the Prosthetic Evaluation Questionnaire Mobility Section (PEQ MS) at the first and the last test to assess perceived potential for mobility using the prosthesis.

RESULTS

Seven long-term prosthesis users were analyzed. Their mean age was 33.9±9.3 years; all were employed, active, and used IC sockets. At the third walking test, the ECW with the MAS(®) was significantly lower than that with the IC socket (p=.016). PEQ MS data also improved significantly at the last evaluation (p<.018).

CONCLUSION

Results suggest that using the MAS(®), lowering the ECW and improving PEQ MS, could be a valid prosthesis design for active TF amputees compared to their usual IC socket.

Comparison of elliptical training, stationary cycling, treadmill walking and overground walking

The extent to which therapeutic, exercise or robotic devices can maximize gait function is a major unresolved issue in neurorehabilitation. Several factors may influence gait outcomes such as similarity of the task to overground walking, degree of coordination within and across limbs, and cycle-to-cycle variability in each device. Our objective was to compare lower extremity kinematics, coordination and variability during four locomotor tasks: overground walking, treadmill walking, elliptical training and stationary cycling in 10 non-disabled adults (6 male; mean age 22.7±2.9 yrs, range 20-29). All first performed four overground walking trials at self-selected speed with mean temporal-spatial data used to pace the other conditions. Joint positions, excursions, and the Gait Deviation Index (GDI) were compared across conditions to evaluate kinematic similarity. Time-series data were correlated within and across limbs to evaluate intralimb and interlimb coordination, respectively. Variability in cadence was quantified to assess how constrained the locomotor rhythm was compared to overground walking. Treadmill walking most closely resembled overground with GDI values nearly overlapping, reinforcing its appropriateness for gait training. Cycling showed the largest GDI difference from overground, with elliptical closer but still a significant distance from all three. Cycling showed greater hip reciprocation Cycling and elliptical showed stronger intralimb synergism at the hip and knee than the other two. Based on kinematics, results suggest that elliptical training may have greater transfer to overground walking than cycling and cycling may be more useful for enhancing reciprocal coordination. Further evaluation of these devices in neurological gait disorders is needed.

Kinematic variability, fractal dynamics and local dynamic stability of treadmill walking

Background

Motorized treadmills are widely used in research or in clinical therapy. Small kinematics, kinetics and energetics changes induced by Treadmill Walking (TW) as compared to Overground Walking (OW) have been reported in literature. The purpose of the present study was to characterize the differences between OW and TW in terms of stride-to-stride variability. Classical (Standard Deviation, SD) and non-linear (fractal dynamics, local dynamic stability) methods were used. In addition, the correlations between the different variability indexes were analyzed.

Methods

Twenty healthy subjects performed 10 min TW and OW in a random sequence. A triaxial accelerometer recorded trunk accelerations. Kinematic variability was computed as the average SD (MeanSD) of acceleration patterns among standardized strides. Fractal dynamics (scaling exponent α) was assessed by Detrended Fluctuation Analysis (DFA) of stride intervals. Short-term and long-term dynamic stability were estimated by computing the maximal Lyapunov exponents of acceleration signals.

Results

TW did not modify kinematic gait variability as compared to OW (multivariate T², p = 0.87). Conversely, TW significantly modified fractal dynamics (t-test, p = 0.01), and both short and long term local dynamic stability (T² p = 0.0002). No relationship was observed between variability indexes with the exception of significant negative correlation between MeanSD and dynamic stability in TW (3 × 6 canonical correlation, r = 0.94).

Conclusions

Treadmill induced a less correlated pattern in the stride intervals and increased gait stability, but did not modify kinematic variability in healthy subjects. This could be due to changes in perceptual information induced by treadmill walking that would affect locomotor control of the gait and hence specifically alter non-linear dependencies among consecutive strides. Consequently, the type of walking (i.e. treadmill or overground) is important to consider in each protocol design.

Comparison of elliptical training, stationary cycling, treadmill walking and overground walking. Electromyographic patterns

The most common functional motor goal of lower extremity rehabilitation is to improve walking ability. For reasons of feasibility, safety or intensity, devices are frequently used to facilitate or augment gait training. The objective of this study was to compare the muscle activity patterns of the rectus femoris and semitendinosus muscles during four conditions: overground walking, treadmill walking, stationary cycling, and elliptical training. Ten healthy adults (six male, four female; mean age 22.7±2.9 years, range 20-29) participated and surface electromyographic data were recorded. Linear envelope curves were generated and time normalized from 0 to 100% cycle. The mean plus three standard deviations from a static trial was used as the threshold for muscle activity. Repeated measures analysis of variance procedures were used to detect differences between conditions. Elliptical training demonstrated greater rectus femoris activity and greater rectus femoris/semitendinosus coactivation than all other conditions. Consistent with previous work, treadmill walking demonstrated greater rectus femoris activity than overground walking. Minimal differences in semitendinosus activation were observed between conditions, limited to lower peak activity during cycling compared to treadmill walking. These results provide normative values for rectus femoris and semitendinosus activation for different locomotor training methods and may assist in selecting the most appropriate training device for specific patients. Clinicians and researchers should also consider the kinematic and kinetic differences between tasks, which cannot necessarily be inferred from muscle activation patterns.

Influence of a locomotor training approach on walking speed and distance in people with chronic spinal cord injury: a randomized clinical trial

BACKGROUND

Impaired walking limits function after spinal cord injury (SCI), but training-related improvements are possible even in people with chronic motor incomplete SCI.

OBJECTIVE

The objective of this study was to compare changes in walking speed and distance associated with 4 locomotor training approaches.

DESIGN

This study was a single-blind, randomized clinical trial.

SETTING

This study was conducted in a rehabilitation research laboratory.

PARTICIPANTS

Participants were people with minimal walking function due to chronic SCI.

INTERVENTION

Participants (n=74) trained 5 days per week for 12 weeks with the following approaches: treadmill-based training with manual assistance (TM), treadmill-based training with stimulation (TS), overground training with stimulation (OG), and treadmill-based training with robotic assistance (LR).

MEASUREMENTS

Overground walking speed and distance were the primary outcome measures.

RESULTS

In participants who completed the training (n=64), there were overall effects for speed (effect size index [d]=0.33) and distance (d=0.35). For speed, there were no significant between-group differences; however, distance gains were greatest with OG. Effect sizes for speed and distance were largest with OG (d=0.43 and d=0.40, respectively). Effect sizes for speed were the same for TM and TS (d=0.28); there was no effect for LR. The effect size for distance was greater with TS (d=0.16) than with TM or LR, for which there was no effect. Ten participants who improved with training were retested at least 6 months after training; walking speed at this time was slower than that at the conclusion of training but remained faster than before training.

LIMITATIONS

It is unknown whether the training dosage and the emphasis on training speed were optimal. Robotic training that requires active participation would likely yield different results.

CONCLUSIONS

In people with chronic motor incomplete SCI, walking speed improved with both overground training and treadmill-based training; however, walking distance improved to a greater extent with overground training.

Influence of a locomotor training approach on walking speed and distance in people with chronic spinal cord injury: a randomized clinical trial

BACKGROUND

Impaired walking limits function after spinal cord injury (SCI), but training-related improvements are possible even in people with chronic motor incomplete SCI.

OBJECTIVE

The objective of this study was to compare changes in walking speed and distance associated with 4 locomotor training approaches.

DESIGN

This study was a single-blind, randomized clinical trial.

SETTING

This study was conducted in a rehabilitation research laboratory.

PARTICIPANTS

Participants were people with minimal walking function due to chronic SCI.

INTERVENTION

Participants (n=74) trained 5 days per week for 12 weeks with the following approaches: treadmill-based training with manual assistance (TM), treadmill-based training with stimulation (TS), overground training with stimulation (OG), and treadmill-based training with robotic assistance (LR).

MEASUREMENTS

Overground walking speed and distance were the primary outcome measures.

RESULTS

In participants who completed the training (n=64), there were overall effects for speed (effect size index [d]=0.33) and distance (d=0.35). For speed, there were no significant between-group differences; however, distance gains were greatest with OG. Effect sizes for speed and distance were largest with OG (d=0.43 and d=0.40, respectively). Effect sizes for speed were the same for TM and TS (d=0.28); there was no effect for LR. The effect size for distance was greater with TS (d=0.16) than with TM or LR, for which there was no effect. Ten participants who improved with training were retested at least 6 months after training; walking speed at this time was slower than that at the conclusion of training but remained faster than before training.

LIMITATIONS

It is unknown whether the training dosage and the emphasis on training speed were optimal. Robotic training that requires active participation would likely yield different results.

CONCLUSIONS

In people with chronic motor incomplete SCI, walking speed improved with both overground training and treadmill-based training; however, walking distance improved to a greater extent with overground training.

Comparison of lower extremity kinematic curves during overground and treadmill running

Researchers conduct gait analyses utilizing both overground and treadmill modes of running. Previous studies comparing these modes analyzed discrete variables. Recently, techniques involving quantitative pattern analysis have assessed kinematic curve similarity in gait. Therefore, the purpose of this study was to compare hip, knee and rearfoot 3-D kinematics between overground and treadmill running using quantitative kinematic curve analysis. Twenty runners ran at 3.35 m/s ± 5% during treadmill and overground conditions while right lower extremity kinematics were recorded. Kinematics of the hip, knee and rearfoot at footstrike and peak were compared using intraclass correlation coefficients. Kinematic curves during stance phase were compared using the trend symmetry method within each subject. The overall average trend symmetry was high, 0.94 (1.0 is perfect symmetry) between running modes. The transverse plane and knee frontal plane exhibited lower similarity (0.86-0.90). Other than a 4.5 degree reduction in rearfoot dorsiflexion at footstrike during treadmill running, all differences were ≤1.5 degrees. 17/18 discrete variables exhibited modest correlations (>0.6) and 8/18 exhibited strong correlations (>0.8). In conclusion, overground and treadmill running kinematic curves were generally similar when averaged across subjects. Although some subjects exhibited differences in transverse plane curves, overall, treadmill running was representative of overground running for most subjects.

The effectiveness of walking as an intervention for low back pain: a systematic review

As current low back pain (LBP) guidelines do not specifically advocate walking as an intervention, this review has explored for the effectiveness of walking in managing acute and chronic LBP. CINAHL, Medline, AMED, EMBASE, PubMed, Cochrane and Scopus databases, as well as a hand search of reference lists of retrieved articles, were searched. The search was restricted to studies in the English language. Studies were included when walking was identified as an intervention. Four studies met inclusion criteria, and were assessed with a quality checklist. Three lower ranked studies reported a reduction in LBP from a walking intervention, while the highest ranked study observed no effect. Heterogeneity of study design made it difficult to draw comparisons between studies. There is only low-moderate evidence for walking as an effective intervention strategy for LBP. Further investigation is required to investigate the strength of effect for walking as a primary intervention in the management of acute and chronic LBP.

Variation in trunk kinematics influences variation in step width during treadmill walking by older and younger adults

Step-by-step variations in step width have been hypothesized to reflect adjustments to swing foot placement in response to preceding frontal plane trunk kinematics. The present study tested this hypothesis while 12 younger and 11 older subjects walked on treadmill for 10min at a self-selected velocity. The relationship between step-by-step variations in step width and frontal plane trunk COM kinematics was determined using multiple regression analysis. Trunk kinematics at midstance were significantly (p<0.001) and strongly (R(2)=0.54) related to the subsequent foot placement supporting the primary hypothesis. Additionally, this relationship was significantly affected by age (p<0.001) and stepping limb (p<0.001). These results implicate feedback driven control of foot trajectory during the swing phase. Further, they provide a biomechanical framework by which loss of frontal plane dynamic stability may result from a step width that is insufficient to decelerate and redirect trunk kinematics in preparation for the next step.

Measures of frontal plane stability during treadmill and overground walking

Given the consequences of falling to the side by older adults, attention has focused on identifying variables associated with changes in lateral stability and fall risk. Step-width (SW) and step-width variability (SWV) have traditionally been associated with such changes. Recently the "margin of stability" (MOS) has been adopted for describing dynamic stability. Although these measures may be influenced by the conditions during which locomotion occurs, only one published within-subject study has compared SW (but not SWV or MOS) during overground and treadmill walking. Therefore, we compared SW, SWV and minimum MOS (MOS(min)) in 10 healthy young subjects walking at self-selected speeds, both overground and on a treadmill. We found SW was significantly larger (p=0.001), and SWV significantly smaller (p=0.001) during treadmill walking, and that these changes were meaningfully correlated between tasks. In contrast, MOS(min) was insensitive to treadmill versus overground walking. This suggested first, that SW and SWV only partially reflect frontal plane stability, and second, that the goal of the central nervous system may be to maintain a constant MOS(min) regardless of task.

Light curtain for detecting footfall instants during treadmill walking--an exploratory study

Footswitches, instrumented insoles, and forceplates are commonly used for detecting footfall instants during treadmill walking. This study aimed to explore the feasibility of using an optoelectronic light curtain for detecting initial foot contact (FC) and toe-off (TO) instants during treadmill walking. A commercial light curtain comprised of an array of parallel infrared light beams was installed 5 mm above the treadmill belt. Ten subjects walked on the treadmill at 0.5, 1.0 and 1.4 m/s and their gait was captured using seven optoelectronic cameras. Footswitches were secured over the heel and big toe of the right foot and the corresponding areas of the shoe. Footfall instants from the light curtain, markers, and foot footswitches were compared with the shoe footswitches serving as a criterion. The respective time differences were computed for each step and used to evaluate the agreement with the criterion and variability across subjects. FC instants from foot footswitches were on average within 10ms of the criterion. Both video and light curtain FC instants were detected at least 30 ms before the criterion. For TO, both the foot footswitches and video instants preceded the criterion. In contrast, the TO from the light curtain occurred >110 ms after the criterion but the variability was the smallest. The results indicated that using a light curtain for detecting footfall instants is feasible. The advantages of light curtain are relatively low cost, no subject preparations, and real-time signals. Greater accuracy is expected with further optimization of the setup.

Determination of preferred walking speed on treadmill may lead to high oxygen cost on treadmill walking

The energy consumption of walking relates to the intensity of physical effort and can be affected by the alterations in walking speed. Therefore, walking speed can be accepted as a crucial, determinant of energy consumption measurement for a walking test. We aimed to investigate the differences in preferred walking speed (PWS) determined both on overground and on a treadmill and, to measure walking energy expenditure and spatio-temporal parameters of gait on a treadmill at both, speeds. Participants (n=26) walked on a treadmill at two pre-determined speeds for 7 min while, indirect calorimetry measurements were being performed. Spatio-temporal parameters were collected, by video-taping during each walking session on a treadmill. The average overground preferred walking speed (O-PWS) was 85.96+/-12.82 m/min and the average treadmill preferred walking speed (T-PWS), was 71.15+/-13.85 m/min. Although T-PWS was lower, oxygen cost was statistically higher when, treadmill walking at T-PWS (0.158+/-0.02 ml/kg/m) than when the treadmill walking at O-PWS, (0.1480+/-0.02 ml/kg/m). Cadence (127+/-9.13 steps/min), stride (134.02+/-14.09 cm) and step length (67.02+/-6.90 cm) on the treadmill walking at O-PWS were significantly higher than cadence (119+/-10 steps/min), stride (117.96+/-14.38 cm) and step length (59.13+/-7.02 cm) on the treadmill walking at TPWS. In conclusion, walking on treadmill using O-PWS is more efficient than walking on treadmill using TPWS, in walking tests. Since using T-PWS for treadmill walking tests overestimates the oxygen cost of walking, O-PWS should be used for oxygen consumption measurement during treadmill walking tests.