Differential deficits in spatial and temporal interlimb coordination during walking in persons with incomplete spinal cord injury

A single sequence of intermittent hypoxia does not alter stretch reflex excitability in able-bodied individuals

Spasticity attributable to exaggerated stretch reflex pathways, particularly affecting the ankle plantar flexors, often impairs overground walking in persons with incomplete spinal cord injury. Compelling evidence from rodent models underscores how exposure to acute intermittent hypoxia (AIH) can provide a unique medium to induce spinal plasticity in key inhibitory pathways mediating stretch reflex excitability and potentially affect spasticity. In this study, we quantify the effects of a single exposure to AIH on the stretch reflex in able-bodied individuals. We hypothesized that a single sequence of AIH will increase the stretch reflex excitability of the soleus muscle during ramp-and-hold angular perturbations applied to the ankle joint while participants perform passive and volitionally matched contractions. Our results revealed that a single AIH exposure did not significantly change the stretch reflex excitability during both passive and active matching conditions. Furthermore, we found that able-bodied individuals increased their stretch reflex response from passive to active matching conditions after both sham and AIH exposures. Together, these findings suggest that a single AIH exposure might not engage inhibitory pathways sufficiently to alter stretch reflex responses in able-bodied persons. However, the generalizability of our present findings requires further examination during repetitive exposures to AIH along with potential reflex modulation during functional movements, such as overground walking.

Comparison of spatio-temporal gait parameters between the GAITRite® platinum plus classic and the GAITRite® CIRFACE among older adults: a retrospective observational study

BACKGROUND

The GAITRite® system is one of the gold standards for gait electronic analysis, especially for older adults. Previous GAITRite® systems were composed of an electronic roll-up walkway. Recently, a new GAITRite® electronic walkway, named CIRFACE, was commercialized. It is composed of a changeable association of stiff plates, unlike previous models. Are the gait parameters measured similar between these two walkways among older adults and according to the cognitive status, the history of falls, and the use of walking aids?

METHODS

In this retrospective observational study, 95 older ambulatory participants (mean, 82.6 ± 5.8 years) were included. Ten spatio-temporal gait parameters were measured simultaneously with the two GAITRite® systems in older adults while walking at comfortable self-selected pace. The GAITRite® Platinum Plus Classic (26') was superimposed on the GAITRite® CIRFACE (VI). Comparisons between the parameters of the two walkways were performed using Bravais-Pearson correlation, between-method differences (corresponding to bias), percentage errors and Intraclass Correlation Coefficients (ICC_2,1). Subgroup analyses were performed according to the cognitive status, the history of falls in the last 12 months and the use of walking aids.

RESULTS

The whole walk parameters recorded by the two walkways were extremely correlated with a Bravais-Pearson correlation coefficient ranging from 0.968 to 0.999, P < .001, indicating a very high correlation. According to the ICC_2,1 calculated for absolute agreement, all gait parameters had excellent reliability (ranging from 0.938 to 0.999). Mean bias for 9 parameters out of 10 were ranged from - 0.27 to 0.54, with clinically acceptable percentage errors (1.2-10.1%). Step length showed a substantially higher bias (1.4 ± 1.2 cm), nevertheless the percentage errors remained clinically acceptable (5%).

CONCLUSION

When walking at comfortable self-selected pace, the standard spatio-temporal walk parameters provided by both the GAITRite® PPC and the GAITRite® CIRFACE seem similar and very highly correlated in older adults with various cognitive or motor status. The data of studies using these systems can be compared and mixed with a very low risk of bias in a meta-analytic process. Also, the geriatric care units can choose the most ergonomic system according to their infrastructure without affecting their gait data.

TRIAL REGISTRATION

NCT04557592 (21/09/2020).

A Wearable Mixed Reality Platform to Augment Overground Walking: A Feasibility Study

Humans routinely modify their walking speed to adapt to functional goals and physical demands. However, damage to the central nervous system (CNS) often results in abnormal modulation of walking speed and increased risk of falls. There is considerable interest in treatment modalities that can provide safe and salient training opportunities, feedback about walking performance, and that may augment less reliable sensory feedback within the CNS after injury or disease. Fully immersive virtual reality technologies show benefits in boosting training-related gains in walking performance; however, they lack views of the real world that may limit functional carryover. Augmented reality and mixed reality head-mount displays (MR-HMD) provide partially immersive environments to extend the virtual reality benefits of interacting with virtual objects but within an unobstructed view of the real world. Despite this potential advantage, the feasibility of using MR-HMD visual feedback to promote goal-directed changes in overground walking speed remains unclear. Thus, we developed and evaluated a novel mixed reality application using the Microsoft HoloLens MR-HMD that provided real-time walking speed targets and augmented visual feedback during overground walking. We tested the application in a group of adults not living with disability and examined if they could use the targets and visual feedback to walk at 85%, 100%, and 115% of each individual’s self-selected speed. We examined whether individuals were able to meet each target gait speed and explored differences in accuracy across repeated trials and at the different speeds. Additionally, given the importance of task-specificity to therapeutic interventions, we examined if walking speed adjustment strategies were consistent with those observed during usual overground walking, and if walking with the MR-HMD resulted in increased variability in gait parameters. Overall, participants matched their overground walking speed to the target speed of the MR-HMD visual feedback conditions (all p-values > 0.05). The percent inaccuracy was approximately 5% across all speed matching conditions and remained consistent across walking trials after the first overall walking trial. Walking with the MR-HMD did not result in more variability in walking speed, however, we observed more variability in stride length and time when walking with feedback from the MR-HMD compared to walking without feedback. The findings offer support for mixed reality-based visual feedback as a method to provoke goal-specific changes in overground walking behavior. Further studies are necessary to determine the clinical safety and efficacy of this MR-HMD technology to provide extrinsic sensory feedback in combination with traditional treatments in rehabilitation.

Degenerative cervical myelopathy delays responses to lateral balance perturbations regardless of predictability

The aim of this study was to quantify balance impairments in standing in people with degenerative cervical myelopathy (PwDCM) in response to external perturbations. PwDCM have damage to their spinal cord due to degeneration of the cervical vertebral column, but little is known about balance. Balance was quantified by capturing kinetics, kinematic, and electromyographic data during standing in response to lateral waist pulls. Participants received pulls during predictable and unpredictable contexts in three stance widths at two magnitudes. In response to lateral waist pulls, PwDCM had larger center of mass excursion (P < 0.001) and delayed gluteus medius electromyography onset (P < 0.001) and peak (P < 0.001) timing. These main effects of history of myelopathy were consistent across predictability, stance width, and magnitude. A multilinear regression determined that gluteus medius peak timing + tibialis anterior peak timing most strongly predicted center of mass excursion (R² = 0.50, P < 0.001). These data suggest that PwDCM have delays in generating voluntary and reactive motor commands, contributing to balance impairments. Future rehabilitation strategies should focus on generating rapid muscular contractions. Additionally, frontal plane postural control is regulated by the gluteus medius and the tibialis anterior, whereas other muscles (e.g. gluteus minimus, ankle invertors/evertors) not studied here may also contribute.NEW & NOTEWORTHY Frontal plane reactive postural control is impaired in persons with degenerative cervical myelopathy because of delayed muscle responses. Additionally, postural control varies across stance width, predictability, and perturbation magnitude.

Multisite Transcutaneous Spinal Stimulation for Walking and Autonomic Recovery in Motor-Incomplete Tetraplegia: A Single-Subject Design

OBJECTIVE

This study investigated the effect of cervical and lumbar transcutaneous spinal cord stimulation (tSCS) combined with intensive training to improve walking and autonomic function after chronic spinal cord injury (SCI).

METHODS

Two 64-year-old men with chronic motor incomplete cervical SCI participated in this single-subject design study. They each underwent 2 months of intensive locomotor training and 2 months of multisite cervical and lumbosacral tSCS paired with intensive locomotor training.

RESULTS

The improvement in 6-Minute Walk Test distance after 2 months of tSCS with intensive training was threefold greater than after locomotor training alone. Both participants improved balance ability measured by the Berg Balance Scale and increased their ability to engage in daily home exercises. Gait analysis demonstrated increased step length for each individual. Both participants experienced improved sensation and bowel function, and 1 participant eliminated the need for intermittent catheterization after the stimulation phase of the study.

CONCLUSION

These results suggest that noninvasive spinal cord stimulation might promote recovery of locomotor and autonomic functions beyond traditional gait training in people with chronic incomplete cervical SCI.

IMPACT

Multisite transcutaneous spinal stimulation may induce neuroplasticity of the spinal networks and confer functional benefits following chronic cervical SCI.

Age-related differences in interlimb coordination during typical gait: An observational study

BACKGROUND

Arm movements during gait are known to alter with increasing age during the slow maturation phase (>3years). It is unclear whether coordination between the arms and legs (i.e. interlimb coordination), which is a measure of gait quality, shows a similar pattern.

RESEARCH QUESTION

to investigate age-related differences in interlimb coordination during gait in typically developing children and adults.

METHODS

In this observational study, 98 typically developing participants were divided into five age-groups: preschool children (G1; 2.9-5.9 years[n = 18]), children (G2; 6.0-9.9 years[n = 22]), pubertal children (G3; 10.0-13.9 years[n = 26]), adolescents (G4; 14.0-18.9 years[n = 14]) and adults (G5; 19.0-35.2 years[n = 18]). Participants walked barefoot at a self-selected walking speed along a 10-m walkway during three-dimensional total-body gait analysis. To examine interlimb coordination, mean continuous relative phase over the gait cycle (MRP) and its variability (sdMRP) were calculated for each combination of limb pairs in the sagittal plane.

RESULTS

MRP increased towards more anti-phase coordination with increasing age in following limb pair combinations: left arm-right arm (median[interquartile range]; G1: 152.0°[126.6;160.7°]-G5: 171.5°[170.0;175.3°]), left arm-left leg (G1: 155.0°[131.3;167.6°]-G5: 170.8°[165.3;173.5°]) and right arm-right leg (G1: 155.7°[135.5;166.0°]-G5: 170.0°[166.4;173.5°]). MRP decreased towards more in-phase coordination from G1 to G5 in left arm-right leg (G1: 24.4°[15.3;45.8°]-G5: 10.5°[6.1;15.6°]) and right arm-left leg (G1: 25.0°[13.7;41.1°]-G5: 9.7°[5.2;16.8°]). sdMRP decreased from G1 to G5 for all limb pair combinations.

SIGNIFICANCE

Interlimb coordination altered with increasing age. First, coordination between the legs and right arm-left leg appeared mature in G1 (aged 2.9-5.9 years). Next, coordination between the ipsilateral limbs seemed mature at 9.9 years, followed by a mature coordination between left arm-right leg at 13.9years. Coordination between the two arms showed ongoing differences until adulthood. These data provide an age-related framework and normative dataset to distinguish age-related differences from pathology in children with neuromotor disorders in clinical practice.

Acute intermittent hypoxia as a potential adjuvant to improve walking following spinal cord injury: evidence, challenges, and future directions

Purpose of Review

The reacquisition and preservation of walking ability are highly valued goals in spinal cord injury (SCI) rehabilitation. Recurrent episodes of breathing low oxygen (i.e., acute intermittent hypoxia, AIH) is a potential therapy to promote walking recovery after incomplete SCI via endogenous mechanisms of neuroplasticity. Here, we report on the progress of AIH, alone or paired with other treatments, on walking recovery in persons with incomplete SCI. We evaluate the evidence of AIH as a therapy ready for clinical and home use and the real and perceived challenges that may interfere with this possibility.

Recent Findings

Repetitive AIH is a safe and an efficacious treatment to enhance strength, walking speed and endurance, as well as, dynamic balance in persons with chronic, incomplete SCI.

Summary

The potential for AIH as a treatment for SCI remains high, but further research is necessary to understand treatment targets and effectiveness in a large cohort of persons with SCI.