Concurrent ankle-assisted movement, biofeedback, and proprioceptive stimulation reduces lower limb motor impairment and improves gait in persons with stroke.

BACKGROUND: Persons with stroke live with residual sensorimotor impairments in their lower limbs (LL), which affects their gait. PURPOSE: We investigated whether these residual impairments and resulting gait deficits can be reduced through concurrently applied assisted movement, biofeedback, and proprioceptive stimulation. METHODS: A robotic device provided impairment-oriented training to the affected LL of 24 persons with stroke (PwS) with moderate-to-severe LL impairment. Participants were given 22-30 training sessions over 2-3 months. During training, the interventional device cyclically dorsiflexed and plantarflexed the ankle at 5 deg/s through ±15 deg for 30 min while the participant assisted with the imposed movement. Concurrently, participants received visual biofeedback of assistive joint torque or agonist EMG while mechanical vibration was applied to the currently lengthening (i.e. antagonist) tendon. RESULTS: Sensorimotor impairment significantly decreased over the training period, which was sustained over 3 months, based on the Fugl-Meyer Assessment (FMA-LL) (p < .001), modified Ashworth scale in dorsiflexors (p < .05), and an ankle strength test (dorsiflexors and plantarflexors) (p < .05). Balance and gait also improved, based on the Tinetti Performance Oriented Mobility Assessment (POMA) (p < .05). CONCLUSION: Impairment-oriented training using a robotic device capable of applying assisted movement, biofeedback, and proprioceptive stimulation significantly reduces LL impairment and improves gait in moderately-to-severely impaired PwS.

Assisted Movement With Proprioceptive Stimulation Augments Recovery From Moderate-To-Severe Upper Limb Impairment During Subacute Stroke Period: A Randomized Clinical Trial.

BACKGROUND: Robotic assisted movement has become an accepted method of treating the moderately-to-mildly impaired upper limb after stroke. OBJECTIVE: To determine whether, during the subacute phase of recovery, a novel type of robotic assisted training reduces moderate-to-severe impairment in the upper limb beyond that resulting from spontaneous recovery and prescribed outpatient therapy. METHODS: A prospective, randomized, double-blinded, placebo-controlled, semi-crossover study of 83 participants. Over 6- to 9-weeks, participants received 18, 30-min training sessions of the hand and wrist. The test intervention consisted of assisted motion, biofeedback, and antagonist muscle vibration delivered by a robotic device. Test Group participants received the test intervention, and Control Group participants received a placebo intervention designed to have no effect. Subsequently, Control Group participants crossed over to receive the test intervention. RESULTS: At enrollment, the average age (±SD) of participants was 57.0 ± 12.8 year and weeks since stroke was 11.6 ± 5.4. The average Fugl-Meyer baseline score of Test Group participants was 20.9, increasing by 10.8 with training, and in Control Group participants was 23.7 increasing by 6.4 with training, representing a significant difference (4.4) in change scores (P = .01). During the crossover phase, Control Group participants showed a significant increase in FMA-UL score (i.e., 4.7 ± 6.7 points, P = .003) as well as in other, more specific measures of impairment. CONCLUSIONS: Robotic impairment-oriented training, as used in this study, can significantly enhance recovery during the subacute phase of recovery. Spontaneous recovery and prescribed outpatient therapy during this phase do not fully exploit the potential for remediating moderate-to-severe upper limb impairment.ClinicalTrials.gov Registry: NCT00609115-Subacute stroke rehabilitation with AMES.

Effect of robotic-assisted ankle training on gait in stroke participants: A case series study.

BACKGROUND: Robotic rehabilitation therapy has grown rapidly during the last two decades allowing researchers and clinicians to deliver high-intensity training to persons with sensorimotor disorders caused by neurological injuries and diseases. METHODS: This case series reports the effect of robot-assisted, impairment-oriented training for persons recovering from stroke on impairment of the paretic ankle as well as on the kinematic and spatiotemporal parameters of gait. Five persons with chronic stroke (>6 months post-stroke) participated in a 10-week training protocol, receiving three, 30-min sessions per week of a robot-assisted therapy. The robot-assisted intervention cyclically induced dorsiflexion and plantarflexion to the ankle at 5 degrees/s through ±15 degrees while the participants assisted with the imposed movement. Concurrently, participants received visual feedback of their active, assistive torque as well as targeted mechanical vibration of the ankle tendons when lengthened by the applied motion. Walking speed, cadence, step length of the non-paretic leg, percentage of paretic single limb support during the gait cycle, and ankle strength were assessed just before training began (baseline), after the last training session (post-training), and 3 months post-training (follow-up). DISCUSSION: Robot-assisted training that provided assisted movement, biofeedback, and proprioceptive stimulation reduced ankle impairment and improved kinematic and spatiotemporal gait parameters, suggesting that impairment-oriented therapy applied to the paretic ankle may provide a valuable adjunct to locomotor therapies in persons with chronic gait disorders due to stroke.

Correction to: Victor Semeonovich Gurfnkel (April 2, 1922-January 14, 2020).

In the original publication of the article.

Assisted movement with proprioceptive stimulation reduces impairment and restores function in incomplete spinal cord injury.

OBJECTIVE: To test whether treatment with assisted movement with enhanced sensation (AMES) using vibration to the antagonist muscle would reduce impairments and restore upper limb function in people with incomplete tetraplegia. DESIGN: Prospective, pre-post study. SETTING: Laboratory and rehabilitation hospital. PARTICIPANTS: We recruited 15 arms from 10 individuals (8 men; mean age, 40.5 y; mean years postspinal cord injury [SCI], 3) with chronic, incomplete tetraplegia. INTERVENTION: Two or three 20-minute sessions per week over 9 to 13 weeks (25 sessions total) on the AMES device, which combines repeated movement with targeted vibration to the antagonist muscle. MAIN OUTCOME MEASURES: Strength and active motion tests on the AMES device; International Standards for the Neurological Classification of SCI (ISNCSCI) motor and sensory examinations; Modified Ashworth Scale (MAS); grasp and release test (GRT); Van Lieshout Test (VLT); and Capabilities of Upper Extremity questionnaire (CUE). RESULTS: The AMES strength test scores improved significantly in metacarpophalangeal flexion (P=.024) and extension (P=.007) and wrist flexion (P=.001) and extension (P<.000). The AMES active motion scores improved in the hand (P=.001) and wrist (P=.001). The MAS and ISNCSCI scores remained unchanged, whereas the GRT scores increased (P=.025). Post hoc analysis showed a trend from pre- to posttreatment (P=.068) and a significant change from pretreatment to 3-month follow-up (P=.046). There was no significant change in the VLT (P=.951) or the CUE (P=.164). Five of the 10 participants reported a return of sensation to the digits after the first, second, or third treatment session. CONCLUSIONS: People with chronic, incomplete tetraplegia may experience improvements in impairments and function after treatment on a device combining assisted movement and proprioceptive stimulation. Further investigation is warranted.

Treatment of severe hand impairment following stroke by combining assisted movement, muscle vibration, and biofeedback.

BACKGROUND AND PURPOSE: Few studies have addressed the rehabilitation of hand function in persons with severe impairment following stroke, and few therapeutic options are available for treatment. We investigated whether an intervention of robot-assisted movement and muscle vibration could reduce impairment and enable hand-opening to a greater extent when combined with torque biofeedback or electromyographic (EMG) biofeedback. METHODS: Forty-three participants with severe hand impairment due to chronic stroke (≥1 year poststroke) were randomized to 1 of 2 treatment groups receiving assisted movement and muscle vibration combined with either torque or EMG biofeedback. Each participant received 30 sessions (30 minutes duration per session) directed at the impaired hand over 10 to 12 weeks. Outcomes were assessed using the Upper Extremity Fugl-Meyer Assessment (UE-FMA), Stroke Impact Scale, and Box-and-Block Test scores. RESULTS: Twenty-eight of 43 participants had no baseline finger extension; the remainder had an average of 23 ± 26 mm extension in the most active finger. Assisted movement and muscle vibration were associated with a significant increase in all outcome measures across both treatment groups, and for the UE-FMA and Stroke Impact Scale within treatment groups, with no significant difference between groups. Based on the Box-and-Block Test scores, the assisted movement and muscle vibration intervention did not restore functional hand-opening to participants with baseline UE-FMA scores less than 17/66, regardless of the form of biofeedback. DISCUSSION AND CONCLUSIONS: Assisted movement and muscle vibration, combined with either EMG or torque biofeedback, appears to reduce upper limb impairment, improve volitional activation of the hand muscles, and restore a modicum of hand function in some persons with severe hand impairment due to chronic stroke.Video Abstract available (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A64) for more insights from the authors.

Contributions of skin and muscle afferent input to movement sense in the human hand.

In the stationary hand, static joint-position sense originates from multimodal somatosensory input (e.g., joint, skin, and muscle). In the moving hand, however, it is uncertain how movement sense arises from these different submodalities of proprioceptors. In contrast to static-position sense, movement sense includes multiple parameters such as motion detection, direction, joint angle, and velocity. Because movement sense is both multimodal and multiparametric, it is not known how different movement parameters are represented by different afferent submodalities. In theory, each submodality could redundantly represent all movement parameters, or, alternatively, different afferent submodalities could be tuned to distinctly different movement parameters. The study described in this paper investigated how skin input and muscle input each contributes to movement sense of the hand, in particular, to the movement parameters dynamic position and velocity. Healthy adult subjects were instructed to indicate with the left hand when they sensed the unseen fingers of the right hand being passively flexed at the metacarpophalangeal (MCP) joint through a previously learned target angle. The experimental approach was to suppress input from skin and/or muscle: skin input by anesthetizing the hand, and muscle input by unexpectedly extending the wrist to prevent MCP flexion from stretching the finger extensor muscle. Input from joint afferents was assumed not to play a significant role because the task was carried out with the MCP joints near their neutral positions. We found that, during passive finger movement near the neutral position in healthy adult humans, both skin and muscle receptors contribute to movement sense but qualitatively differently. Whereas skin input contributes to both dynamic position and velocity sense, muscle input may contribute only to velocity sense.

Progression of forearm intravenous regional anesthesia with ropivacaine.

The progression of sensory blockade in the hand following a forearm Bier block with ropivacaine is currently unknown. The hands of 10 healthy adult human subjects were anesthetized with ropivacaine, and their sensitivities to cold and touch were tested until the completion of anesthesia. On average, insensitivity to cold occurred uniformly throughout the hand within 9 mins; however, touch sensation was not complete until approximately 20 mins after injection. The spread of anesthesia occurred in a semisystematic way, spreading proximally and distally from the site of injection (mid-dorsum of the hand), and, at a slower rate, from the dorsum of the hand to the palm.

Method to measure tone of axial and proximal muscle.

The control of tonic muscular activity remains poorly understood. While abnormal tone is commonly assessed clinically by measuring the passive resistance of relaxed limbs, no systems are available to study tonic muscle control in a natural, active state of antigravity support. We have developed a device (Twister) to study tonic regulation of axial and proximal muscles during active postural maintenance (i.e. postural tone). Twister rotates axial body regions relative to each other about the vertical axis during stance, so as to twist the neck, trunk or hip regions. This twisting imposes length changes on axial muscles without changing the body's relationship to gravity. Because Twister does not provide postural support, tone must be regulated to counteract gravitational torques. We quantify this tonic regulation by the restive torque to twisting, which reflects the state of all muscles undergoing length changes, as well as by electromyography of relevant muscles. Because tone is characterized by long-lasting low-level muscle activity, tonic control is studied with slow movements that produce "tonic" changes in muscle length, without evoking fast "phasic" responses. Twister can be reconfigured to study various aspects of muscle tone, such as co-contraction, tonic modulation to postural changes, tonic interactions across body segments, as well as perceptual thresholds to slow axial rotation. Twister can also be used to provide a quantitative measurement of the effects of disease on axial and proximal postural tone and assess the efficacy of intervention.

Reduced performance in balance, walking and turning tasks is associated with increased neck tone in Parkinson's disease.

Rigidity or hypertonicity is a cardinal symptom of Parkinson's disease (PD). We hypothesized that hypertonicity of the body axis affects functional performance of tasks involving balance, walking and turning. The magnitude of axial postural tone in the neck, trunk and hip segments of 15 subjects with PD (both ON and OFF levodopa) and 15 control subjects was quantified during unsupported standing in an axial twisting device in our laboratory as resistance to torsional rotation. Subjects also performed six functional tests (walking in a figure of eight [Figure of Eight], Timed Up and Go, Berg Balance Scale, supine rolling task [rollover], Functional Reach, and standing 360-deg turn-in-place) in the ON and OFF state. Results showed that PD subjects had increased tone throughout the axis compared to control subjects (p=0.008) and that this increase was most prominent in the neck. In PD subjects, axial tone was related to functional performance, but most strongly for tone at the neck and accounted for an especially large portion of the variability in the performance of the Figure of Eight test (r(OFF)=0.68 and r(ON)=0.74, p<0.05) and the Rollover test (r(OFF)=0.67 and r(ON)=0.55, p<0.05). Our results suggest that neck tone plays a significant role in functional mobility and that abnormally high postural tone may be an important contributor to balance and mobility disorders in individuals with PD.

Assisted movement with enhanced sensation (AMES): coupling motor and sensory to remediate motor deficits in chronic stroke patients.

BACKGROUND: Conventional methods of rehabilitation in patients with chronic, severe motor impairments after stroke usually do not lessen paresis. OBJECTIVE: A novel therapeutic approach (assisted movement with enhanced sensation [AMES]) was employed in a medical device phase I clinical trial to reduce paresis and spasticity and, thereby, to improve motor function. METHODS: Twenty subjects more than 1 year poststroke with severe motor disability of the upper or lower extremity were studied. A robotic device cycled the ankle or the wrist and fingers at 5 degrees/s through +/-17.5 degrees in flexion and extension while the subject assisted this motion. Feedback of the subject's active torque was displayed on a monitor. Simultaneously, 2 vibrators applied a 60 pps stimulus to the tendons of the lengthening muscles, alternating from flexors to extensors as the joint rotation reversed from extension to flexion, respectively. Subjects treated themselves at home for 30 min/day for 6 months. Every other day prior to treatment, the therapy device performed automated tests of strength and joint positioning. Functional testing was performed prior to enrollment, immediately after completing the protocol, and 6 months later. Functional tests included gait and weight distribution (lower extremity subjects only) and the Stroke Impact Scale. RESULTS: Most subjects improved on most tests, and gains were sustained for 6 months in most subjects. No safety problems arose. CONCLUSION: The AMES strategy appears safe and possibly effective in patients with severe chronic impairments. The mechanism underlying these gains is likely to be multifactorial.

Postural muscle tone in the body axis of healthy humans.

Across the entire human body, postural tone might play its most critical role in the body's axis because the axis joins the four limbs and head into a single functioning unit during complex motor tasks as well as in static postures. Although postural tone is commonly viewed as low-level, tonic motor activity, we hypothesized that postural tone is both tonically and dynamically regulated in the human axis even during quiet stance. Our results describe the vertical distribution of postural muscle tone in the neck, trunk, and hips of standing human adults. Each subject stood blindfolded on a platform that axially rotated the neck, trunk, or pelvis at 1 degrees /s and +/-10 degrees relative to the neutral position (i.e., facing forward). The measured resistance to axial rotation was highest in the trunk and lowest in the neck and was characterized by several nonlinear features including short-range stiffness and hysteresis. In half of the subjects, axial muscle activity was relatively constant during axial rotation, and in the other half, muscle activity was modulated by lengthening and shortening reactions, i.e., decreasing activity in lengthening muscles and increasing activity in shortening muscles, respectively. Axial resistance to rotation was reduced in subjects whose muscle activity was modulated. The results indicate that axial tone is modulated sensitively and dynamically, this control originates, at least in part, from tonic lengthening and shortening reactions, and a similar type of control appears to exist for postural tone in the proximal muscles of the arm.

Scaling and non-scaling of muscle activity, kinematics, and dynamics in sit-ups with different degrees of difficulty.

The purpose of this study was to investigate how the CNS adjusts motor patterns for variants of a complex axial movement-the sit-up. Adjustments were induced by changing the support surface contact and mass distribution of the body. Healthy adults performed straight-legged sit-ups, 3 s in duration, with support added to or removed from the lumbar trunk, or with mass added to the head or to the legs. Each of these interventions either increased or decreased the difficulty of the task. The study addressed the extent to which changes in sit-up difficulty are compensated by scaling of muscle activity, kinematics, and dynamics versus the extent to which they are compensated by changing discretely the motor pattern. The analysis of muscle activity, kinematics, and dynamics focused on the first 30-40% of the sit-up-the trunk flexion phase-since this is the most critical part of the movement. Our results demonstrate that, in some respects, sit-up kinematics and dynamics scaled with difficulty, but in other respects, they did not. Muscle activity also scaled, in many respects, but in more difficult sit-ups, abdominal flexor activity decreased instead of increased. Non-scaling changes in these parameters suggest that complex movements, such as the sit-up, may require discrete changes in motor pattern in order to deal with large loads, which challenge the available leverage.

Illusory changes in head position induced by neck muscle vibration can alter the perception of elbow position.

Acuity for elbow joint position sense (JPS) is reduced when head position is modified. Movement of the head is associated with biomechanical changes in the neck and shoulder musculoskeletal system, which may explain changes in elbow JPS. The present study aimed to determine whether elbow JPS is also influenced by illusory changes in head position. Simultaneous vibration of sternocleidomastoid (SCM) and the contralateral splenius was applied to 14 healthy adult human subjects. Muscle vibration or passive head rotation was introduced between presentation and reproduction of a target elbow position. Ten out of 14 subjects reported illusions consistent with lengthening of the vibrated muscles. In these 10 subjects, absolute error for elbow JPS increased with left SCM/right splenius vibration but not with right SCM/left splenius vibration. Absolute error also increased with right rotation, with a trend for increased error with left rotation. These results demonstrated that both actual and illusory changes in head position are associated with diminished acuity for elbow JPS, suggesting that the influence of head position on upper limb JPS depends, at least partially, on perceived head position.

Proprioceptive weighting changes in persons with low back pain and elderly persons during upright standing.

The purpose of this study was to examine whether postural instability observed in persons with spinal pain and in elderly persons is due to changes in proprioception and postural control strategy. The upright posture of 20 young and 20 elderly persons, with and without spinal pain, was challenged by vibrating ankle muscles (i.e. tibialis anterior, triceps surae) or paraspinal muscles. Center of pressure displacement was recorded using a force plate. Persons with spinal pain were more sensitive to triceps surae vibration and less sensitive to paraspinal vibration than persons without spinal pain. Elderly persons were more sensitive to tibialis anterior vibration than young healthy persons. These results suggest that spinal pain and aging may lead to changes in postural control by refocusing proprioceptive sensitivity from the trunk to the ankles.

Motor coordination can be fully understood only by studying complex movements.

In this chapter, we use the sit-up to illustrate the complexity of coordination in movements that involve many muscles, joints, degrees of freedom, and high levels of muscle activity. Complex movements often involve the body axis. In addition to the intentional, focal part of any voluntary movement, complex movements also include "associated movements" that are not consciously controlled, but are necessary for the movement to succeed. Some associated movements serve a purpose, and others may not. During sitting up, the leg-lift is a purposive associated movement, whereas three-joint flexion is a non-purposive associated movement. The control of complex movements is also likely to be complex and, we argue, is hierarchically controlled. Associated movements may, themselves, be hierarchically organized and triggered by lower brain structures, local changes in neuronal excitability, and sensory feedback. Complex movements typically involve a high level of mobility. Because this mobility can lead to instability, anticipatory postural adjustments, a type of purposive associated movement, are commonly used to regulate posture. Thus, a number of important aspects of motor coordination can only be revealed by the study of complex movements.

Position sensitivity of human muscle spindles: single afferent and population representations.

The representation of joint position at rest and during movement was investigated in 44 muscle spindle primary afferents originating from the extensor carpi radialis brevis (ECRb) and extensor digitorum (ED) of normal human subjects. Position sensitivity was estimated for each afferent, and 43 of 44 were position sensitive. In each trial, six sequential ramp-and-hold movements (2-6 degrees, 2 degrees/s, total 24 degrees) flexed the relaxed wrist, beginning from the angle at which the afferent was just recruited. Joint position was represented by three specific features of afferent firing patterns: the steady-state firing rate during the 4-s hold period between ramps, the initial burst at the beginning of each ramp, and the ramp increase in firing rate later in the movement. The position sensitivity of the initial burst (1.27 +/- 0.90 pps/degree, mean +/- SD) was several times higher than that of the hold period (0.40 +/- 0.30 pps/degree) and not different from that of the ramp increase in firing rate (1.36 +/- 0.68 pps/degree). The wrist position sensitivities of ECRb and ED afferents were equivalent, as were their recruitment angles and angular ranges of position sensitivity. Muscle spindle afferents, both individually and as a population, were shown to represent static joint position via the hold rate and the initial burst. Afferents were recruited over the entire 110 degree range of wrist positions investigated; however, the angular range over which each feature represented joint position was extremely limited (approximately 15 degrees). The population response, based on the summed activity of the 43 afferents, was monotonically related to joint position, and it was strongly influenced by the afferent recruitment pattern, but less so by the position sensitivities of the individual afferents.