Virtual reality-enhanced walking in people post-stroke: effect of optic flow speed and level of immersion on the gait biomechanics

BACKGROUND

Optic flow-the apparent visual motion experienced while moving-is absent during treadmill walking. With virtual reality (VR), optic flow can be controlled to mediate alterations in human walking. The aim of this study was to investigate (1) the effects of fully immersive VR and optic flow speed manipulation on gait biomechanics, simulator sickness, and enjoyment in people post-stroke and healthy people, and (2) the effects of the level of immersion on optic flow speed and sense of presence.

METHODS

Sixteen people post-stroke and 16 healthy controls performed two VR-enhanced treadmill walking sessions: the semi-immersive GRAIL session and fully immersive head-mounted display (HMD) session. Both consisted of five walking trials. After two habituation trials (without and with VR), participants walked three more trials under the following conditions: matched, slow, and fast optic flow. Primary outcome measures were spatiotemporal parameters and lower limb kinematics. Secondary outcomes (simulator sickness, enjoyment, and sense of presence) were assessed with the Simulator Sickness Questionnaire, Visual Analogue Scales, and Igroup Presence Questionnaire.

RESULTS

When walking with the immersive HMD, the stroke group walked with a significantly slower cadence (-3.69strides/min, p = 0.006), longer stride time (+ 0.10 s, p = 0.017) and stance time for the unaffected leg (+ 1.47%, p = 0.001) and reduced swing time for the unaffected leg (- 1.47%, p = 0.001). Both groups responded to the optic flow speed manipulation such that people accelerated with a slow optic flow and decelerated with a fast optic flow. Compared to the semi-immersive GRAIL session, manipulating the optic flow speed with the fully immersive HMD had a greater effect on gait biomechanics whilst also eliciting a higher sense of presence.

CONCLUSION

Adding fully immersive VR while walking on a self-paced treadmill led to a more cautious gait pattern in people post-stroke. However, walking with the HMD was well tolerated and enjoyable. People post-stroke altered their gait parameters when optic flow speed was manipulated and showed greater alterations with the fully-immersive HMD. Further work is needed to determine the most effective type of optic flow speed manipulation as well as which other principles need to be implemented to positively influence the gait pattern of people post-stroke.

TRIAL REGISTRATION NUMBER

The study was pre-registered at ClinicalTrials.gov (NCT04521829).

Skeletal muscle changes in the first three months of stroke recovery: a systematic review

BACKGROUND

Rehabilitation is important in the first months after a stroke for recovery of functional ability, but it is also challenging, since distinct recovery trajectories are seen. Therefore, studying the early changes in muscle characteristics over time (e.g. muscle strength, muscle mass and muscle volume), which are known to be associated with functional abilities, may deepen our understanding of underlying recovery mechanisms of stroke survivors.

OBJECTIVE

This systematic review aims to describe the longitudinal changes in skeletal muscles, including muscle strength, muscle mass and muscle volume, during the first 3 months post-stroke.

METHODS

Electronic searches were conducted in Medline, Scopus and CENTRAL. Longitudinal cohort studies or controlled interventional trials that report data about patients in the first 3 months after stroke were identified. Skeletal muscle characteristics should be measured at least twice within 3 months post-stroke by objective, quantitative assessment methods (e.g. dynamometry, ultrasound, computed tomography). Effect sizes were calculated as Hedges' g using standardized mean differences.

RESULTS

A total of 38 studies (1,097 subjects) were found eligible. Results revealed an average increase on the paretic side for upper and lower limb muscle strength (small to moderate effect sizes), whereas muscle thickness decreased (moderate to large effect sizes). Similar, but smaller, effects were found on the non-paretic side. There were insufficient data available to draw conclusions about lean muscle mass and muscle cross-sectional area. No studies aimed at investigating distinct trajectories of the muscle changes.

CONCLUSION

Muscle strength and thickness changes during the first 3 months after stroke in both the paretic and non-paretic side. Future studies should aim to understand "how" the stroke-induced muscle strength changes are achieved. Exploring existing data from longitudinal studies, by using cluster analyses, such as pattern recognition, could add to the current knowledge-base.

The Effect of physical therapy on impairments in COVID-19 patients from intensive care to home rehabilitation: A rapid review

OBJECTIVE

Guidelines regarding physical therapy for COVID-19 patients are often based on expert opinion. Recent clinical trials have reported effects on several rehabilitation outcomes in COVID-19 patients. This review summarizes the effects of physical therapy in COVID-19 patients.

DATA SOURCES

PubMed, Web of Science and Scopus databases were systematically searched for studies investigating the effect of any physical therapy modality on impairments in adult COVID-19 patients. Included studies were (non)-randomized controlled trials, pre-experimental studies, and cohort studies in which a pre-post analysis was performed.

DATA EXTRACTION

After the screening process, data of interest were extracted from eligible studies and their risk of bias was assessed. Included outcome measures were divided into 3 groups: pulmonary function, physical function, and psychosocial function.

DATA SYNTHESIS

A total of 15 studies were included in this review. Physical therapy seems to have positive effects on pulmonary function, physical function, and psychosocial function. However, these effects differ between clinical settings (e.g. home care, intensive care unit, inpatient units). Due to the low-to-moderate quality of the included studies, no robust conclusions can be drawn.

CONCLUSION

Further high-quality research is required, taking into account the different clinical settings, in order to draw conclusions about the effectiveness of physical therapy on impairments in COVID-19 patients.

Muscle changes after stroke and their impact on recovery: time for a paradigm shift? Review and commentary

In stroke rehabilitation there is a growing body of evidence that not all patients have the same potential to recover. Understanding the processes that give rise to the heterogeneous treatment responses in stroke survivors will lay foundations for any conceivable advance in future rehabilitation interventions. This review was set out to shine new light on the debate of biomarkers in stroke rehabilitation by linking fundamental insights from biogerontological sciences to neurorehabilitation sciences. In particular, skeletal muscle changes and inflammation are addressed as two potential constructs from which biomarkers for stroke rehabilitation can be derived. Understanding the interplay between these constructs as well as their relation to recovery could enhance stroke rehabilitation in the future. The rationale for the selection of these constructs is three-fold: first, recent stroke literature emphasizes the importance of identifying muscle wasting (also called stroke-induced muscle wasting) in stroke patients, a concept that is widely investigated in geriatrics but less in the stroke population. Second, insights from transdisciplinary research domains such as gerontology have shown that inflammation has severe catabolic effects on muscles, which may impede rehabilitation outcomes such as gait recovery. Last, it has been proven that (high-intensity) muscle strengthening exercises have strong anti-inflammatory effects in a non-stroke population. Therefore, an evidence-based rationale is presented for developing research on individual changes of muscle and inflammation after a stroke.

The Effect of Optic Flow Speed on Active Participation During Robot-Assisted Treadmill Walking in Healthy Adults

This study aimed to investigate: 1) the effect of optic flow speed manipulation on active participation during robot-assisted treadmill walking (RATW), 2) the influence of the type of virtual environment, and 3) the level of motion sickness and enjoyment. Twenty-eight healthy older adults were randomized in two groups: "stimulus rich" Park group (50% male, 61± 6 year) and "stimulus poor" Hallway group (43% male, 62± 5 year). Subjects walked in the Lokomat with immersive virtual reality (VR) with a matched, slow and fast optic flow speed, each lasting 7 minutes. Active participation was measured by continuously assessing the human-machine interaction torques at the hip and knee joints and muscle activity of the Vastus Medialis and Biceps Femoris. Motion sickness and enjoyment were assessed with the Simulator Sickness Questionnaire (SSQ) and Physical Activity Enjoyment Scale (PACES) respectively. In both groups optic flow speed manipulation in both directions led to a decrease in bilateral hip interaction torques towards flexion at the end of the stance phase compared to matched speed. In the Hallway group, walking with slow optic flow elicited 32% more muscle activity of the Vastus Medialis. There were no significant differences between both groups for the SSQ and PACES. Optic flow speed manipulation appears to have only a small effect on the active participation of healthy people during RATW. The type of virtual environment did not affect their activity, motion sickness or enjoyment. However, the addition of immersive VR during RATW was well tolerated and enjoyable. Further research with patients is necessary.

Physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors

PURPOSE

To examine physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors; compare these outcomes with aerobic exercise recommendations; and investigate the effect of robotic assistance.

MATERIALS AND METHODS

Twelve non-ambulatory stroke survivors (67 ± 11 years-old, 84 ± 38 d post-stroke) participated. Subjects walked three times 20 min (1 session/day) in the Lokomat: once with conventional exercise parameters, once with 60% robotic assistance and once with 100% robotic assistance. Gas exchange and heart rate were monitored continuously. Perceived exertion was assessed every 3 min during walking.

RESULTS

During conventional robot-assisted treadmill walking, net perceived exertion (0-14 scale) significantly increased between minute 6 (median = 2, interquartile range = 4) and 18 (median = 5, interquartile range = 4). Net physiological responses did not significantly change over time. Throughout exercise, percentage of predicted heart rate reserve was significantly below the 40% threshold (medians: 11-14%) and percentage of predicted maximum heart rate reached the 55% threshold (medians: 59-60%). Perceived exertion reached the 11-point threshold halfway. Net physiological responses and perceived exertion did not significantly differ between 60% and 100% robotic assistance.

CONCLUSIONS

The assistance level that non-ambulatory stroke survivors require at their highest tolerable walking speed seems too high to sufficiently stress the cardiorespiratory system during robot-assisted treadmill walking.Implications for rehabilitationThe exercise intensity of 20-minute conventional robot-assisted treadmill walking can be low, and might be too low to challenge the cardiorespiratory system of non-ambulatory stroke survivors.Lowering the level of robotic assistance from 100% to 60% does not seem to increase the exercise intensity of 20-minute robot-assisted treadmill walking.

Physiological Responses and Perceived Exertion During Robot-Assisted and Body Weight-Supported Gait After Stroke

INTRODUCTION

Physiological responses are rarely considered during walking after stroke and if considered, only during a short period (3-6 minutes). The aims of this study were to examine physiological responses during 30-minute robot-assisted and body weight-supported treadmill and overground walking and compare intensities with exercise guidelines.

METHODS

A total of 14 ambulatory stroke survivors (age: 61 ± 9 years; time after stroke: 2.8 ± 2.8 months) participated in 3 separate randomized walking trials. Patients walked overground, on a treadmill, and in the Lokomat (60% robotic guidance) for 30 minutes at matched speeds (2.0 ± 0.5 km/h) and matched levels of body weight support (BWS; 41% ± 16%). Breath-by-breath gas analysis, heart rate, and perceived exertion were assessed continuously.

RESULTS

Net oxygen consumption, net carbon dioxide production, net heart rate, and net minute ventilation were about half as high during robot-assisted gait as during body weight-supported treadmill and overground walking ( P < .05). Net minute ventilation, net breathing frequency, and net perceived exertion significantly increased between 6 and 30 minutes (respectively, 1.8 L/min, 2 breaths/min, and 3.8 units). During Lokomat walking, exercise intensity was significantly below exercise recommendations; during body weight-supported overground and treadmill walking, minimum thresholds were reached (except for percentage of heart rate reserve during treadmill walking).

CONCLUSION

In ambulatory stroke survivors, the oxygen and cardiorespiratory demand during robot-assisted gait at constant workload are considerably lower than during overground and treadmill walking at matched speeds and levels of body weight support. Future studies should examine how robotic devices can be Future studies should examine how robotic devices can be exploited to induce aerobic exercise.