Mechanically induced stumbling during human treadmill walking (original) (raw)
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Stepping responses to treadmill perturbations vary with severity of motor deficits in human SCI
Journal of Neurophysiology
In this study, we investigated the responses to tread perturbations during human stepping on a treadmill. Our approach was to test the effects of perturbations to a single leg using a split-belt treadmill in healthy participants and in participants with varying severity of spinal cord injury (SCI). We recruited 11 people with incomplete SCI and 5 noninjured participants. As participants walked on an instrumented treadmill, the belt on one side was stopped or accelerated briefly during midstance to late stance. A majority of participants initiated an unnecessary swing when the treadmill was stopped in midstance, although the likelihood of initiating a step was decreased in participants with more severe SCI. Accelerating or decelerating one belt of the treadmill during stance altered the characteristics of swing. We observed delayed swing initiation when the belt was decelerated (i.e., the hip was in a more flexed position at time of swing) and advanced swing initiation with accelerat...
Method for evoking a trip-like response using a treadmill-based perturbation during locomotion
Journal of Biomechanics, 2014
Because trip-related falls account for a significant proportion of falls by patients with amputations and older adults, the ability to repeatedly and reliably simulate a trip or evoke a trip-like response in a laboratory setting has potential utility as a tool to assess trip-related fall risk and as a training tool to reduce fall risk. This paper describes a treadmill-based method for delivering postural perturbations during locomotion to evoke a trip-like response and serve as a surrogate for an overground trip. Subjects walked at a normalized velocity in a Computer Assisted Rehabilitation Environment (CAREN). During single-limb stance, the treadmill belt speed was rapidly changed, thereby requiring the subject to perform a compensatory stepping response to avoid falling. Peak trunk flexion angle and peak trunk flexion velocity during the initial compensatory step following the perturbation were smaller for responses associated with recoveries compared to those associated with falls. These key fall prediction variables were consistent with the outcomes observed for laboratory-induced trips of older adults. This perturbation technique also demonstrated that this method of repeated but randomly delivered perturbations can evoke consistent, within-subject responses.
Muscular Responses and Movement Strategies During Stumbling Over Obstacles
2000
Schillings, A. M., B.M.H. Van Wezel, Th. Mulder, and J. Duysens. Muscular responses and movement strategies during stumbling over obstacles. J. Neurophysiol. 83: 2093J. Neurophysiol. 83: -2102J. Neurophysiol. 83: , 2000. Although many studies have investigated reflexes after stimulation of either cutaneous or proprioceptive afferents, much less is known about responses after more natural perturbations, such as stumbling over an obstacle. In particular, the phase dependency of these responses and their relation to the stumbling behavior has received little attention. Hence response strategies during stumbling reactions after perturbations at different times in the swing phase of gait were studied. While subjects walked on a treadmill, a rigid obstacle unexpectedly obstructed the forward sway of the foot. All subjects showed an "elevating strategy" after early swing perturbations and a "lowering strategy" after late swing perturbations. During the elevating strategy, the foot was directly lifted over the obstacle through extra knee flexion assisted by ipsilateral biceps femoris (iBF) responses and ankle dorsiflexion assisted by tibialis anterior (iTA) responses. Later, large rectus femoris (iRF) activations induced knee extension to place the foot on the treadmill. During the lowering strategy, the foot was quickly placed on the treadmill and was lifted over the obstacle in the subsequent swing. Foot placement was actively controlled by iRF and iBF responses related to knee extension and deceleration of the forward sway. Activations of iTA mostly preceded the main ipsilateral soleus (iSO) responses. For both strategies, four response peaks could be distinguished with latencies of ϳ40 ms (RP1), ϳ75 ms (RP2), ϳ110 ms (RP3), and ϳ160 ms (RP4). The amplitudes of these response peaks depended on the phase in the step cycle. The phase-dependent modulation of the responses could not be accounted for by differences in stimulation or in background activity and therefore is assumed to be premotoneuronal in origin. In mid swing, both the elevating and lowering strategy could occur. For this phase, the responses of the two strategies could be compared in the absence of phase-dependent response modulation. Both strategies had the same initial electromyographic responses till ϳ100 ms (RP1-RP2) after perturbation. The earliest response (RP1) is assumed to be a short-latency stretch reflex evoked by the considerable impact of the collision, whereas the second (RP2) has features reminiscent of cutaneous and proprioceptive responses. Both these responses did not determine the behavioral response strategy. The functionally important response strategies depended on later responses (RP3-RP4). These data suggest that during stumbling reactions, as a first line of defense, the CNS releases a relatively aspecific response, which is followed by an appropriate behavioral response to avoid the obstacle.
Muscular responses and movement strategies during stumbling over obstacles. J Neurophysiol
Journal of Neurophysiology
Schillings, A. M., B.M.H. Van Wezel, Th. Mulder, and J. Duysens. Muscular responses and movement strategies during stumbling over obstacles. J. Neurophysiol. 83: 2093J. Neurophysiol. 83: -2102J. Neurophysiol. 83: , 2000. Although many studies have investigated reflexes after stimulation of either cutaneous or proprioceptive afferents, much less is known about responses after more natural perturbations, such as stumbling over an obstacle. In particular, the phase dependency of these responses and their relation to the stumbling behavior has received little attention. Hence response strategies during stumbling reactions after perturbations at different times in the swing phase of gait were studied. While subjects walked on a treadmill, a rigid obstacle unexpectedly obstructed the forward sway of the foot. All subjects showed an "elevating strategy" after early swing perturbations and a "lowering strategy" after late swing perturbations. During the elevating strategy, the foot was directly lifted over the obstacle through extra knee flexion assisted by ipsilateral biceps femoris (iBF) responses and ankle dorsiflexion assisted by tibialis anterior (iTA) responses. Later, large rectus femoris (iRF) activations induced knee extension to place the foot on the treadmill. During the lowering strategy, the foot was quickly placed on the treadmill and was lifted over the obstacle in the subsequent swing. Foot placement was actively controlled by iRF and iBF responses related to knee extension and deceleration of the forward sway. Activations of iTA mostly preceded the main ipsilateral soleus (iSO) responses. For both strategies, four response peaks could be distinguished with latencies of ϳ40 ms (RP1), ϳ75 ms (RP2), ϳ110 ms (RP3), and ϳ160 ms (RP4). The amplitudes of these response peaks depended on the phase in the step cycle. The phase-dependent modulation of the responses could not be accounted for by differences in stimulation or in background activity and therefore is assumed to be premotoneuronal in origin. In mid swing, both the elevating and lowering strategy could occur. For this phase, the responses of the two strategies could be compared in the absence of phase-dependent response modulation. Both strategies had the same initial electromyographic responses till ϳ100 ms (RP1-RP2) after perturbation. The earliest response (RP1) is assumed to be a short-latency stretch reflex evoked by the considerable impact of the collision, whereas the second (RP2) has features reminiscent of cutaneous and proprioceptive responses. Both these responses did not determine the behavioral response strategy. The functionally important response strategies depended on later responses (RP3-RP4). These data suggest that during stumbling reactions, as a first line of defense, the CNS releases a relatively aspecific response, which is followed by an appropriate behavioral response to avoid the obstacle.
Stumbling reactions in man: influence of corticospinal input
Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, 1998
The aim of this study was to evaluate the degree of contribution of supraspinal input to the generation of the compensatory leg muscle activation following stance perturbation. Therefore, evoked motor response (EMR) input-output relations of two different motor tasks were compared at 3 distinct periods: (1) the basic period of muscular activity during standing, i.e. when no additional cortical or spinal activity due to the different tasks is to be expected, (2) the pre-movement period with low background activity, when different spinal and cortical inputs to the motoneuronal pool can be assumed and (3) the period of plateau EMG activity of compensatory and voluntary motor task. Transcranial magnetic stimulation (TMS) just below the motor threshold was applied randomly at 19 different time-intervals before and during the onset of stance perturbation and for comparison during an equivalent voluntary foot-dorsiflexion task. Recordings of electromyographic (EMG) activity from the tibialis anterior (TA) and corresponding ankle-joint movements were made from both legs. Forwarddirected displacements were induced by randomly-timed ramp impulses of constant acceleration upon a moveable platform. For comparison, leg muscle EMG was recorded during isometric foot dorsiflexion during stance while leaning back against a support. The stance perturbations were followed by a compensatory response (CR) in the TA with a mean onset time of 81 ms. During the basic period of muscular activity and the period of plateau EMG activity there was no significant difference of the input-output relation between stance perturbation and the voluntary motor task. However, in the voluntary task compared with the CR, there was significantly greater inputoutput relation (facilitation) of the EMR in the TA following TMS, which may be related to an increased cortical influence. In contrast to this result of the CR following stance perturbation, a facilitation of the EMR was described for hand muscles under corresponding conditions of automatic compensation for muscle stretch, suggesting a transcortical reflex loop. This difference in the results from upper and lower extremity muscles favors the assumption of a predominantly spinal generation of the TA-CR following stance perturbation.
Mechanically induced ankle inversion during human walking and jumping
Journal of Neuroscience Methods, 2002
A new method to study sudden ankle inversions during human walking and jumping is presented. Ankle inversions of 258 were elicited using a box containing a trap door. During the gait task, subjects walked at a speed of 4 km/h. At a pre-programmed delay after left heel strike, an electromagnet released the box on the treadmill. This delay enabled the subject to step on the box without having to change the walking cadence. During the jumping task, subjects jumped from a 30 cm high platform on the box in a standardised way. In both tasks 20 stimulus and 20 control trials were presented randomly. The average tilting velocity of the trap door during the stimulus trials was 4038/s during the walking task and 5958/s during the jumping task. For the control trials a tilting of 08 was used. With this method it is possible to evoke reproducible ankle inversions causing characteristic EMG responses in six lower leg muscles.
Technology and Health Care, 2017
BACKGROUND: Treadmills are used frequently in rehabilitation enabling neurologically impaired subjects to train walking while being assisted by therapists. Numerous studies compared walking on treadmill and overground for unperturbed but not also perturbed conditions. OBJECTIVE: The objective of this study was to compare stepping responses (step length, step width and step time) during overground and treadmill walking in a group of healthy subjects where balance assessment robots applied perturbing pushes to the subject's pelvis in sagittal and frontal planes. METHODS: During walking in both balance assessment robots (overground and treadmill-based) with applied perturbations the stepping responses of a group of seven healthy subjects were assessed with a motion tracking camera. RESULTS: The results show high degree of similarity of stepping responses between overground and treadmill walking for all perturbation directions. Both devices reproduced similar experimental conditions with relatively small standard deviations in the unperturbed walking as well as in perturbed walking. CONCLUSIONS: Based on these results we may conclude that stepping responses following perturbations can be studied on an instrumented treadmill where ground reaction forces can be readily assessed which is not the case during perturbed overground walking.
Balance-corrective responses to unexpected perturbations at the arms during treadmill walking
Journal of neurophysiology, 2014
The arms have been shown to be involved in the regulation of balance during walking. The use of a walking aid enhances balance by increasing the base of support and reducing the load on the legs by partly transferring it to the arms. However, when actively engaged during a balance task, perturbations to the arms can destabilize balance. Previous studies have investigated postural adjustments associated with focal arm movements during standing and walking. However, balance-corrective reactions to unexpected perturbations to the arms during walking have not been well studied. In the present study, subjects walked on a treadmill while grasping a pair of handles when sudden perturbations were delivered by displacing the handles in the forward or backward direction. Instructing subjects to oppose the displacement of the handles resulted in strong responses in the arms that were accompanied by activation of muscles in the legs, comparable to those observed in other balance disturbance stu...
2014
The present work focuses on the motor control after a sudden ankle dorsiflexion mechanically evoked during the swing phase of running. We investigated the running pattern adjustments and the muscular responses, reflex or not, realized after the perturbation. Results show that the running pattern adjustments are appropriate and modulated within the swing phase. The step length and duration are maintained as constant as possible to continue running at the speed imposed by the treadmill without stumbling or falling. The only strong modification is a decreased impact observed after the perturbations evoked in late swing, when the ankle is still in a more dorsiflexed position at foot touch-down. In human subjects, the stretch of a muscle evokes a series of electromyographic reflex bursts in this muscle called ‘stretch reflex’ responses. The sudden ankle dorsiflexion induces a stretch of the plantarflexors muscles. Our results show that the early component of the reflex response is suppre...