Hybrid functional electrical stimulation exercise training alters the relationship between spinal cord injury level and aerobic capacity

Exercise prescription for persons with spinal cord injury: a review of physiological considerations and evidence-based guidelines

Persons with spinal cord injury (SCI) experience gains in fitness, physical and mental health from regular participation in exercise and physical activity. Due to changes in physiological function of the cardiovascular, nervous, and muscular systems, general population physical activity guidelines and traditional exercise prescription methods are not appropriate for the SCI population. Exercise guidelines specific to persons with SCI recommend progressive training beginning at 20 min of moderate to vigorous intensity aerobic exercise twice per week transitioning to 30 min three times per week, with strength training of the major muscle groups two times per week. These population-specific guidelines were designed considering the substantial barriers to physical activity for persons with SCI and can be used to frame an individual exercise prescription. Rating of perceived exertion (i.e., perceptually regulated exercise) is a practical way to indicate moderate to vigorous intensity exercise in community settings. Adapted exercise modes include arm cycle ergometry, hybrid arm-leg cycling, and recumbent elliptical equipment. Body weight-supported treadmill training and other rehabilitation modalities may improve some aspects of health and fitness for people with SCI if completed at sufficient intensity. Disability-specific community programs offer beneficial opportunities for persons with SCI to experience quality exercise opportunities but are not universally available.

Post-processing Peak Oxygen Uptake Data Obtained During Cardiopulmonary Exercise Testing in Individuals With Spinal Cord Injury: A Scoping Review and Analysis of Different Post-processing Strategies

OBJECTIVES

To review the evidence regarding the most common practices adopted with cardiopulmonary exercise testing (CPET) in individuals with spinal cord injury (SCI), with the following specific aims to (1) determine the most common averaging strategies of peak oxygen uptake (V̇o2peak), (2) review the endpoint criteria adopted to determine a valid V̇o2peak, and (3) investigate the effect of averaging strategies on V̇o2peak values in a convenience sample of individuals with SCI (between the fourth cervical and sixth thoracic spinal segments).

DATA SOURCES

Searches for this scoping review were conducted in MEDLINE (PubMed), EMBASE, and Web Science.

STUDY SELECTION

Studies were included if (1) were original research on humans published in English, (2) recruited adults with traumatic and non-traumatic SCI, and (3) V̇o2peak reported and measured directly during CPET to volitional exhaustion. Full-text review identified studies published before April 2021 for inclusion.

DATA EXTRACTION

Extracted data included authors name, journal name, publication year, participant characteristics, and comprehensive information relevant to CPET.

DATA SYNTHESIS

We extracted data from a total of 197 studies involving 4860 participants. We found that more than 50% of studies adopted a 30-s averaging strategy. A wide range of endpoint criteria were used to confirm the attainment of maximal effort. In the convenience sample of individuals with SCI (n=30), the mean V̇o2peak decreased as epoch (ie, time) lengths increased. Reported V̇o2peak values differed significantly (P<.001) between averaging strategies, with epoch length explaining 56% of the variability.

CONCLUSIONS

The adoption of accepted and standardized methods for processing and analyzing CPET data are needed to ensure high-quality, reproducible research, and inform population-specific normative values for individuals with SCI.

Serotonin 1A Receptor Pharmacotherapy and Neuroplasticity in Spinal Cord Injury

Spinal cord injury is associated with damage in descending and ascending pathways between brainstem/cortex and spinal neurons, leading to loss in sensory-motor functions. This leads not only to locomotor reduction but also to important respiratory impairments, both reducing cardiorespiratory engagement, and increasing cardiovascular risk and mortality. Moreover, individuals with high-level injuries suffer from sleep-disordered breathing in a greater proportion than the general population. Although no current treatments exist to restore motor function in spinal cord injury (SCI), serotoninergic (5-HT) 1A receptor agonists appear as pharmacologic neuromodulators that could be important players in inducing functional improvements by increasing the activation of spared motoneurons. Indeed, single therapies of serotoninergic 1A (5-HT_1A) agonists allow for acute and temporary recovery of locomotor function. Moreover, the 5-HT_1A agonist could be even more promising when combined with other pharmacotherapies, exercise training, and/or spinal stimulation, rather than administered alone. In this review, we discuss previous and emerging evidence showing the value of the 5HT_1A receptor agonist therapies for motor and respiratory limitations in SCI. Moreover, we provide mechanistic hypotheses and clinical impact for the potential benefit of 5-HT_1A agonist pharmacology in inducing neuroplasticity and improving locomotor and respiratory functions in SCI.

Hybrid Functional Electrical Stimulation improves anaerobic threshold in first three years following spinal cord injury

The purpose of the present investigation was to assess the effects of whole-body exercise on anaerobic threshold in individuals with spinal cord injury (SCI). Maximal oxygen uptake (VO2max) and oxygen uptake at anaerobic threshold (AT) were measured before and after 6 months of hybrid functional electrical stimulation row training in 47 participants with SCI aged 19-63, neurological levels of injury C4-L1, American Spinal Injury Association Impairment Scale grades A-D, and time since injury at enrollment from 3 months to 40 years. Changes in VO2max differed with time since injury, with greater increases earlier post injury. The early chronic group (<3 years since injury; n=31) increased VO2max from 1.65 ± 0.54 L/min at baseline to 1.83 ± 0.66 L/min at 6 months (p<0.05), while the late chronic group (>3 years since injury; n=16) did not change (1.42 ± 0.44 at baseline to 1.47 ± 0.41 L/min at 6 months, p=0.36). Consistent with VO2max changes, AT increased in the early chronic group (1.03 ± 0.31 to 1.20 ± 0.40 L/min, p<0.05) and did not change in the late chronic group (0.99 ± 0.31 to 0.99 ± 0.26 L/min, p=0.92). Cumulative duration of exercise training was positively correlated to change in VO2max (r=0.475, p<0.05) but not to change in AT. Hybrid functional electrical stimulation row training is effective for increasing aerobic capacity and anaerobic threshold in individuals with spinal cord injury; however, these fitness benefits are only significant in individuals initiating the exercise intervention within three years of injury.

Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review

CONTEXT

This review synthesizes the findings of previous research studies on the cardiovascular and metabolic benefits of aerobic exercise for individuals with tetraplegia secondary to spinal cord injury. They are often less active due to muscular paralysis, sensory loss, and sympathetic nervous system dysfunction that result from injury. Consequently, these persons are at higher risk for exercise intolerance and secondary health conditions.

OBJECTIVE

To evaluate the evidence concerning efficacy of aerobic exercise training for improving health and exercise performance in persons with tetraplegia from cervical injury.

METHODS

The search engines PubMed and Google Scholar were used to locate published research. The final 75 papers were selected on the basis of inclusion criteria. The studies were then rank-ordered using Physiotherapy Evidence Database.

RESULTS

Studies combining individuals with tetraplegia and paraplegia show that voluntary arm-crank training can increase mean peak power output by 33%. Functional electrical stimulation leg cycling was shown to induce higher peak cardiac output and stroke volume than arm-crank exercise. A range of peak oxygen uptake (VO_2peak) values have been reported (0.57-1.32 L/min). Both VO_2peak and cardiac output may be enhanced via increased muscle pump in the legs and venous return to the heart. Hybrid exercise (arm-crank and functional electrical stimulation leg cycling) can result in greater peak oxygen uptake and cardiovascular responses.

CONCLUSION

Evidence gathered from this systematic review of literature is inconclusive due to the lack of research focusing on those with tetraplegia. Higher power studies (level 1-3) are needed with the focus on those with tetraplegia.

Clinical Benefits and System Design of FES-Rowing Exercise for Rehabilitation of Individuals with Spinal Cord Injury: A Systematic Review

OBJECTIVE

To comprehensively and critically appraise the clinical benefits and engineering designs of functional electrical stimulation (FES)-rowing for management of individuals with spinal cord injury (SCI).

DATA SOURCES

Electronic database searches were conducted in Cumulative Index to Nursing & Allied Health Literature, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Excerpta Medica database, Emcare, Medline, PubMed, Scopus, and Web of Science databases from inception to May 12, 2020.

STUDY SELECTION

Search terms used were synonyms of "spinal cord injury" for Population and "Electric Stimulation (Therapy)/ and rowing" for Intervention. Two reviewers independently assessed articles based on the following inclusion criteria: recruited individuals with SCI; had aerobic FES-rowing exercise as study intervention; reported cardiovascular, muscular, bone mineral density, or metabolic outcomes; and examined engineering design of FES-rowing systems. Of the 256 titles that were retrieved in the primary search, 24 were included in this study.

DATA EXTRACTION

Study characteristics, quality, participants' characteristics, test descriptions, and results were independently extracted by 2 reviewers. The quality of studies was assessed with the Downs and Black checklist.

DATA SYNTHESIS

Comparison of peak oxygen consumption (V̇_o2peak) rates showed that V̇_o2peak during FES-rowing was significantly higher than arm-only exercise; FES-rowing training improved V̇_o2peak by 11.2% on average (95% confidence interval, 7.25-15.1), with a 4.1% (95% confidence interval, 2.23-5.97) increase in V̇_o2peak per month of training. FES-rowing training reduced bone density loss with increased time postinjury. The rowing ergometer used in 2 studies provided motor assistance during rowing. Studies preferred manual stimulation control (n=20) over automatic (n=4).

CONCLUSIONS

Our results suggest FES-rowing is a viable exercise for individuals with SCI that can improve cardiovascular performance and reduce bone density loss. Further randomized controlled trials are needed to better understand the optimal set-up for FES-rowing that maximizes the rehabilitation outcomes.

Effect of 6-Month Exercise Training on Neurovascular Function in Spinal Cord Injury

INTRODUCTION

Although previous data show exacerbated incidence of cognitive impairment after spinal cord injury (SCI), the physiology that underlies this postinjury cognitive decline is unknown. One potential culprit is impairment in the ability of cerebral vasculature to alter regional flow to sustain neural metabolism (i.e., "neurovascular coupling"). We hypothesized that cerebrovascular responses to a working memory task are impaired in individuals with SCI and can be improved by aerobic exercise training.

METHODS

We assessed the effect of injury and 6-month full-body aerobic exercise training on the cerebral blood flow response to cognitive demand (i.e., neurovascular coupling) in 24 individuals with SCI and 16 controls. Cognitive demand was introduced in a graded fashion using a working memory task.

RESULTS

Reaction time tended to be higher in individuals with SCI, especially those with high-level (≥T4) injuries, possibly due to upper motor impairments. Neurovascular coupling was graded across task difficulty (P < 0.01) and followed cognitive demand, and injury itself did not have a significant effect (group effect P = 0.99, interaction P = 0.70). Individuals with low-level injuries (

CONCLUSION

Previously reported cognitive impairment after SCI may reflect a decline in neurovascular coupling primarily due to physical deconditioning rather than injury itself. The latter can be mitigated by aerobic exercise training.

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MESH Headings

• Adult
• Cardiorespiratory Fitness
• Cognitive Dysfunction/etiology
• Cognitive Dysfunction/physiopathology
• Cognitive Dysfunction/therapy
• Exercise Therapy
• Female
• Humans
• Male
• Neurovascular Coupling
• Spinal Cord Injuries/physiopathology
• Spinal Cord Injuries/rehabilitation
• Young Adult

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Gains in aerobic capacity with whole-body functional electrical stimulation row training and generalization to arms-only exercise after spinal cord injury

STUDY DESIGN

Longitudinal study in adults (n = 27; 19-40 years old) with tetraplegic or paraplegic spinal cord injury (SCI).

OBJECTIVES

Determine physiological adaptations and generalizable fitness effects of 6 months of whole-body exercise training using volitional arm and functional electrical stimulation (FES) leg rowing.

SETTING

Outpatient hospital-based exercise facility and laboratory.

METHODS

Participants enrolled in hybrid FES-row training (FESRT) and performed peak exercise tests with arms-only (AO; baseline and 6 months) and FES rowing (baseline, 3, 6 months).

RESULTS

Participants demonstrated increased aerobic capacity (VO_2peak) after FESRT (p < 0.001, n_p² = 0.56) that tended to be higher when assessed with FES than AO rowing tests (0.15 ± 0.20 vs. 0.04 ± 0.22 L/min; p = 0.10). Changes in FES and AO VO_2peak were significantly correlated (r = 0.55; p < 0.01), and 11 individuals demonstrated improvements (>6%) on both test formats. Younger age was the only difference between those who showed generalization of training effects and those who did not (mean age 26.6 ± 5.6 vs. 32.0 ± 5.7 years; p < 0.05) but changes in FES VO_2peak correlated to time since injury in individuals <2 years post-SCI (r = -0.51, p < 0.01, n = 24). Lastly, VO_2peak improvements were greater during the first 3 months vs. months 4-6 (+7.0% vs. +3.9%; p < 0.01) which suggests early training adaptations during FESRT.

CONCLUSIONS

Gains in aerobic capacity after whole-body FESRT are better reflected during FES-row testing format. They relate to high-intensity exercise and appear early during training, but they may not generalize to equivalent increases in AO exercise in all individuals with SCI.

Relationship of Spinal Cord Injury Level and Duration to Peak Aerobic Capacity With Arms-Only and Hybrid Functional Electrical Stimulation Rowing

OBJECTIVE

The aim of the study was to assess the relationship of spinal cord injury level and duration to peak aerobic capacities during arms-only rowing compared with hybrid Functional Electrical Stimulation (FES)-rowing.

DESIGN

Comparison of peak aerobic capacity (VO2), peak ventilation, peak respiratory exchange ratio, and peak heart rate were measured during arms-only rowing and FES-rowing obtained from graded exercise tests.

RESULTS

Peak aerobic values were strongly related to injury level and injury duration for both arms-only rowing (r = 0.67, P < 0.05) and FES-rowing (r = 0.61, P < 0.05). Peak aerobic capacities were greater across all injury levels and durations with FES-rowing compared with arms-only rowing. Differences in VO2 were inversely related to injury level (r = 0.55, P < 0.05) with greater increases in VO2 in higher level injuries. Injury durations of less than 2 yrs had greater percent increases in VO2 with FES-rowing.

CONCLUSIONS

FES-rowing acutely post injury may have the greatest effect to maintain function and improve VO2. This impact seems to be greatest in those with higher level injuries.

More Than Just a Game: The Public Health Impact of Sport and Physical Activity for People With Disabilities (The 2017 DeLisa Lecture)

Although people with disabilities make up a large proportion of our global population and are known to be disproportionately impacted by sedentary lifestyles leading to chronic disease, programs promoting physical activity often fail to address their unique needs. Both environmental and attitudinal factors also act as barriers to full participation. In this context, increasing evidence shows the positive impact of physical activity and sport on outcomes related to physical health, mental health, community participation, and, in some cases, neurorecovery for people with disabilities. Thus, participation should be seen not only as a medical intervention but also as a rights-based issue. We, as physiatrists, can be agents of change by promoting concepts of universal design and inclusion in physical activity and sport programs.

Energy Expenditure as a Function of Activity Level After Spinal Cord Injury: The Need for Tetraplegia-Specific Energy Balance Guidelines

The World Health Organization recognizes obesity as a global and increasing problem for the general population. Because of their reduced physical functioning, people with spinal cord injury (SCI) face additional challenges for maintaining an appropriate whole body energy balance, and the majority with SCI are overweight or obese. SCI also reduces exercise capacity, particularly in those with higher-level injury (tetraplegia). Tetraplegia-specific caloric energy expenditure (EE) data is scarce. Therefore, we measured resting and exercise-based energy expenditure in participants with tetraplegia and explored the accuracy of general population-based energy use predictors. Body composition and resting energy expenditure (REE) were measured in 25 adults with tetraplegia (C4/5 to C8) and in a sex-age-height matched group. Oxygen uptake, carbon dioxide production, heart rate, perceived exertion, and exercise intensity were also measured in 125 steady state exercise trials. Those with motor-complete tetraplegia, but not controls, had measured REE lower than predicted (mean = 22% less, p < 0.0001). REE was also lower than controls when expressed per kilogram of lean mass. Nine had REE below 1200 kcal/day. We developed a graphic compendium of steady state EE during arm ergometry, wheeling, and hand-cycling. This compendium is in a format that can be used by persons with tetraplegia for exercise prescription (calories, at known absolute intensities). EE was low (55–450 kcal/h) at the intensities participants with tetraplegia were capable of maintaining. If people with tetraplegia followed SCI-specific activity guidelines (220 min/week) at the median intensities we measured, they would expend 563–1031 kcal/week. Participants with tetraplegia would therefore require significant time (4 to over 20 h) to meet a weekly 2000 kcal exercise target. We estimated total daily EE for a range of activity levels in tetraplegia and compared them to predicted values for the general population. Our analysis indicated that the EE values for sedentary through moderate levels of activity in tetraplegia fall well below predicted sedentary levels of activity for the general population. These findings help explain sub-optimal responses to exercise interventions after tetraplegia, and support the need to develop tetraplegia-specific energy-balance guidelines that reflects their unique EE situation.

The influence of level of spinal cord injury on adipose tissue and its relationship to inflammatory adipokines and cardiometabolic profiles

OBJECTIVE

Level of injury (LOI) and the role of adipose tissue and its proinflammatory adipokines in cardiometabolic dysfunction following spinal cord injury (SCI) remains poorly understood. We aim to examine the influence of LOI on adipose tissue and its relationship to proinflammatory adipokines and cardiometabolic profiles following SCI.

DESIGN

Cross sectional and correlational study.

SETTING

Clinical hospital and academic setting.

PARTICIPANTS

Forty-seven individuals with chronic motor complete SCI (age 43.8±11.5 y, BMI: 27.3±5.3) were classified as having tetraplegia (TSCI; n=12) or paraplegia (PSCI; n=35).

INTERVENTION

Non applicable.

OUTCOME MEASURES

Visceral (VAT) and subcutaneous (SAT) adipose tissue volumes were measured using magnetic resonance imaging. Proinflammatory adipokines (tumor neurosis factor-α, interleukin-6 (IL-6), plasminogen activatable inhibitor-1, thrombin-activatable fibrinolysis inhibitor, and high-sensitivity c-reactive protein) and cardiovascular, carbohydrate, and lipid profiles were assessed according to standard techniques.

RESULTS

VAT volume was greater in TSCI versus PSCI (p=0.042); however, after covarying for age this significance was lost (p>0.05). IL-6 was significantly elevated in TSCI (p<0.05), while other markers of inflammation generally were elevated, but did not reach statistical significance (p>0.05). Systolic blood pressure and total cholesterol were significantly lower in TSCI (p<0.05), while fasting glucose was significantly lower in PSCI (p<0.05). A number of proinflammatory adipokines and cardiometabolic markers significantly correlated with adipose tissue depots by LOI (p<0.05).

CONCLUSION

The results show that LOI does not influence the distribution of adipose tissue, but does influence proinflammatory adipokines and cardiometabolic profiles following SCI. Further research is needed to evaluate impact of lean body mass on these findings.

Effect of inspiratory muscle training (IMT) on aerobic capacity, respiratory muscle strength and rate of perceived exertion in paraplegics

Objectives: The purpose is to study the effect of inspiratory muscle training on aerobic capacity, respiratory muscle strength and rate of perceived exertion in paraplegics.Study Design: Randomized controlled trial.Settings: Rehabilitation department in Indian Spinal Injuries Centre, New Delhi.Participants: A sample of 30 paraplegics (T1-T12) were randomly allocated into two groups: inspiratory muscle training (IMT) group and control group.Interventions: The IMT group received inspiratory muscle training for 15 minutes 5 times a week for 4 weeks whereas the control group was given breathing exercises.Outcome measures: Maximal inspiratory pressure(MIP), maximal expiratory pressure (MEP), modified Borg's scale (MBS), 12 minute wheelchair aerobic test (12MWAT), multistage fitness test (MSFT), and 6 minutes push test (6MPT).Results: Out of 30 participants, 27 completed the study. The results show that after four weeks of IMT training, there were significant improvements in mean change scores of IMT group as compared to control group. Participants in IMT group performed better on 12MWAT (P = 0.001), MSFT (P = 0.001) and 6MPT (P = 0.001). Improvements in MIP scores (P = 0.001), MEP scores (P = 0.001) and MBS scores (P = 0.004) were also seen in IMT group.Conclusion: Both groups showed significant improvements, however inspiratory muscle training was seen to be more effective than deep breathing exercises for improving aerobic capacity, respiratory muscle strength and rate of perceived exertion in paraplegics.

Ventilation Limits Aerobic Capacity after Functional Electrical Stimulation Row Training in High Spinal Cord Injury

PURPOSE

In the able-bodied, exercise training results in increased ventilatory capacity to meet increased aerobic demands of trained skeletal muscle. However, after spinal cord injury (SCI), peak ventilation can be limited by pulmonary muscle denervation. In fact, peak ventilation may restrict aerobic capacity in direct relation to injury level. Hybrid functional electrical stimulation (FES) exercise training results in increased aerobic capacity and dissociation between aerobic capacity and injury level in those with injuries at T3 and below. However, injuries above T3 have the greatest pulmonary denervation, and ventilatory capacity may restrict the increase in aerobic capacity with hybrid FES training.

METHODS

We assessed relationships among injury level, peak ventilation, and peak aerobic capacity and calculated oxygen uptake efficiency slope during hybrid FES exercise in 12 individuals (1 female) with SCI at level T2 to C4 (injury duration = 0.33-33 yr, age = 20-60 yr), before and after 6 months of FES-row training (FES-RT).

RESULTS

Training increased peak aerobic capacity by 12% (P = 0.02) with only a modest increase in peak ventilation (7 of 12 subjects, P = 0.09). Both before and after training, injury level was directly related to peak ventilation (R = 0.48 and 0.43) and peak aerobic capacity (R = 0.70 and 0.55). Before training, the relationship of peak aerobic capacity to peak ventilation was strong (R = 0.62), however, after training, this relationship became almost completely linearized (R = 0.84). In addition, oxygen uptake efficiency slope increased by 11% (P < 0.05) after FES-RT.

CONCLUSION

Despite the ability to increase exercise capacity via hybrid FES exercise, the inability to increase peak ventilation beyond limits set by SCI level in those with high-level injuries (above T3) appears to restrict aerobic capacity.

Implications of altered autonomic control on sports performance in athletes with spinal cord injury

It is well known that athletes with spinal cord injury (SCI) may experience altered autonomic physiology that impacts their exercise capacity and sports performance. This is particularly relevant given the ever-increasing number of individuals with SCI who are actively engaged in sports at all levels, from community-based adaptive sports to elite Paralympic competitions. As such, the purpose of this article is to review the present literature regarding the implications of altered autonomic control on the safety and performance of athletes with SCI. A particular emphasis will be placed on the autonomic aspects of cardiovascular and thermoregulatory control in the athlete population, as well as the implications of autonomic dysreflexia in enhancing sports performance. Further research is needed to understand the autonomic factors that influence athletes with SCI in order to ensure optimal and safe sports competition. Additionally, this information is crucially relevant to the coaches, sports administrators, and team medical staff who work closely with athletes with SCI.