Student Blog 05: Investigating the effects of powered exoskeleton-based physical activity in adults with neurological impairments.

Damien Duddy is a PhD researcher based in ATU Donegal and Sports Lab Northwest

Damien Duddy is a PhD researcher based in ATU Donegal and Sports Lab Northwest currently preparing for a viva voce examination. This PhD project originally began as a Masters by Research which was successfully transferred to a Doctorate programme after year two. Undergraduate studies consisted of completing a higher certificate in Sports Studies which was proceeded by successfully completing a BSc (Hons) in Sport and Exercise with Performance with first class honours.

This PhD project was completed in ATU Donegal, Letterkenny Campus in partnership with The No Barriers Foundation.

Neurological impairments are disorders of the central and peripheral nervous systems that affect the brain, spinal cord, nerves, muscles, and neuromuscular junctions. Individuals with neurological impairments often adopt a sedentary lifestyle, mainly due to reduced gait function and mobility. In turn, adopting a sedentary lifestyle may increase the likelihood of those with neurological impairments developing cardiorespiratory and metabolic diseases, secondary health conditions, and elements of physical deconditioning. Although wheelchairs are used to participate in exercise and sports competitions, they may not result in an adequate amount of physical activity per day. However, powered exoskeletons have recently emerged as a new rehabilitation tool that enable individuals with neurological impairments to stand and walk overground, by externally supporting body mass, generating steps with motors attached to both the hip and knee joints. The powered exoskeletons used throughout this research were the Ekso GT and the Ekso NR which were both developed by Ekso Bionics and owned by the No Barriers Foundation.

This research firstly involved completing a systematic review, which examined the effects of exoskeleton gait training on cardiorespiratory function and gait performance. This was proceeded by a feasibility study conducted within an able-bodied population (N = 8). The purpose of the feasibility study was to assess the effectiveness of exoskeleton based physical activity on cardiorespiratory, muscle activation, and movement responses, as well as assessing the safety and practicality of the methodology to be applied in future research among individuals with neurological impairments. All participants completed two 12-minute treadmill walking bouts at the same fixed speeds (4 mins at 1, 2, and 3 km·h−1); the first was completed without the exoskeleton and the second walking bout was completed with the Ekso GT. The feasibility study highlighted that exoskeleton treadmill walking significantly increased cardiorespiratory demands at all walking speeds, as well as vastus lateralis peak muscle activation recordings and lower limb acceleration and angular velocity at various speeds.

The feasibility study informed the design of a 12-week exoskeleton-based physical activity and home-based resistance training programme – The Rehabilitation of neurologically Impaired and Spinal cord injured: Exoskeleton (RISE) trial. A single group of participants with neurological impairments (N = 6; multiple sclerosis: n = 4; spinal cord injury: n = 1; traumatic brain injury: n = 1). All participants completed one exoskeleton-based physical activity session per week (60 mins) and two home-based resistance training sessions per week, which were designed based on individual capabilities, the World Health Organisations physical activity guidelines, and the American College of Sports Medicines resistance training guidelines. At week one, six, and twelve, participants completed assessment sessions, which included a two-minute standstill in the exoskeleton to record estimated resting parameters, which was followed by a six-minute walk test, where the objective was to walk as far and as fast as possible within the six-minute timeframe. Like the feasibility study, cardiorespiratory response, muscle activation, and movement were assessed throughout; and functional mobility and quality-of-life were also recorded using a specific exoskeleton screening protocol and the EQ-5D-5L questionnaire, respectively.

The findings from the RISE trial illustrated significant improvements in walking speed, walking distance, and step count, while maintaining a similar or slightly lower cardiorespiratory output. Significant improvements were noted for left knee and right hip acceleration and left knee angular velocity. No significant improvements were noted for emotional response, functional mobility, or quality-of-life despite a notable 20.9-point increase in self-perceived overall health scores. However, participants with multiple sclerosis displayed significantly greater overall quality-of-life scores throughout the RISE trial compared to participants with spinal cord injury and traumatic brain injury.

When comparing exoskeleton walking versus the pre-walk standstill, exoskeleton walking elicited a significant increase in cardiorespiratory demands at baseline, mid, and post-intervention. The six-minute walk test also produced a significant increase in left medial gastrocnemius (calf muscle) and right rectus femoris (thigh muscle) peak muscle activity at baseline; and left medial gastrocnemius and right soleus (calf muscles) peak muscle activity at mid-intervention when compared to the pre-walk standstill.

Therefore, powered exoskeleton walking may provide exoskeleton users with adequate cardiorespiratory stimulus to enhance cardiorespiratory fitness, subsequently reducing sedentary time, and mitigating the risk of developing secondary health conditions, namely, obesity, diabetes, osteoporosis, cardiovascular and metabolic diseases, and overall mortality. Additionally, with the increase in gait performance, adopting powered exoskeleton gait training into a neurological rehabilitation programme may help the exoskeleton user target the World Health Organisations physical activity guidelines for health for adults living with disabilities, which recommend 150 to 300 minutes of moderate-intensity aerobic physical activity, 75 to 150 minutes of vigorous-intensity aerobic physical activity, or an equivalent combination of both per week. For additional health adaptations, it is recommended that adults with disabilities undertake muscle strengthening activities involving all major muscle groups completed at a moderate intensity at least twice per week. These guidelines were used to inform the design of the RISE trial. In turn, this may help mitigate the risk of developing secondary health conditions such as, diabetes, obesity, osteoporosis, physical deconditioning, cardiorespiratory and metabolic diseases, and overall mortality. Hence, where possible, powered exoskeletons should be included in neurological rehabilitation programmes to improve overall health.

In summary, powered exoskeletons may be an appropriate support method to help individuals with neurological impairments increase physical activity levels, reduce sedentary behaviour, improve gait function, systolic blood pressure, cardiorespiratory fitness, and lower extremity movement, and muscle activation. This research provides a solid foundation for future research, which should focus on recruit larger sample sizes and subgroups and incrementally increase the volume, intensity, and/or frequency of exoskeleton walking after week six, as greater adaptations were observed from week one to week six compared to week six to week twelve.  

ResearchGate: https://researchgate.net/profile/Damien-Duddy

ORCID: 0000-0002-8374-0957