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Rapid muscle fatigue during functional electrical stimulation (FES)-evoked muscle contractions in individuals with spinal cord injury (SCI) is a significant limitation to attaining health benefits of FES-exercise. Delaying the onset of muscle fatigue is often cited as an important goal linked to FES clinical efficacy. Although the basic concept of fatigue-resistance has a long history, recent advances in biomedical engineering, physiotherapy and clinical exercise science have achieved improved clinical benefits, especially for reducing muscle fatigue during FES-exercise. This review evaluated the methodological quality of strategies underlying muscle fatigue-resistance that have been used to optimize FES therapeutic approaches. The review also sought to synthesize the effectiveness of these strategies for persons with SCI in order to establish their functional impacts and clinical relevance. Published scientific literature pertaining to the reduction of FES-induced muscle fatigue was identified through searches of the following databases: Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed and Nature, from the earliest returned record until June 2015. Titles and abstracts were screened to obtain 35 studies that met the inclusion criteria for this systematic review. Following the evaluation of methodological quality (mean (SD), 50 (6) %) of the reviewed studies using the Downs and Black scale, the largest treatment effects reported to reduce muscle fatigue mainly investigated isometric contractions of limited functional and clinical relevance (n = 28). Some investigations (n = 13) lacked randomisation, while others were characterised by small sample sizes with low statistical power. Nevertheless, the clinical significance of emerging trends to improve fatigue-resistance during FES included (i) optimizing electrode positioning, (ii) fine-tuning of stimulation patterns and other FES parameters, (iii) adjustments to the mode and frequency of exercise training, and (iv) biofeedback-assisted FES-exercise to promote selective recruitment of fatigue-resistant motor units. Although the need for further in-depth clinical trials (especially RCTs) was clearly warranted to establish external validity of outcomes, current evidence was sufficient to support the validity of certain techniques for rapid fatigue-reduction in order to promote FES therapy as an integral part of SCI rehabilitation. It is anticipated that this information will be valuable to clinicians and other allied health professionals administering FES as a treatment option in rehabilitation and aid the development of effective rehabilitation interventions.

Objectives The objective of this review was to summarize and appraise evidence on functional electrical stimulation (FES) cycling exercise after spinal cord injury (SCI), in order to inform the development of evidence-based clinical practice guidelines. Methods PubMed, the Cochrane Central Register of Controlled Trials, EMBASE, SPORTDiscus, and CINAHL were searched up to April 2021 to identify FES cycling exercise intervention studies including adults with SCI. In order to capture the widest array of evidence available, any outcome measure employed in such studies was considered eligible. Two independent reviewers conducted study eligibility screening, data extraction, and quality appraisal using Cochranes’ Risk of Bias or Downs and Black tools. Each study was designated as a Level 1, 2, 3 or 4 study, dependent on study design and quality appraisal scores. The certainty of the evidence for each outcome was assessed using GRADE ratings (‘High’, ‘Moderate’, ‘Low’, or ‘Very low’). Results Ninety-two studies met the eligibility criteria, comprising 999 adults with SCI representing all age, sex, time since injury, lesion level and lesion completeness strata. For muscle health (e.g., muscle mass, fiber type composition), significant improvements were found in 3 out of 4 Level 1–2 studies, and 27 out of 32 Level 3–4 studies (GRADE rating: ‘High’). Although lacking Level 1–2 studies, significant improvements were also found in nearly all of 35 Level 3–4 studies on power output and aerobic fitness (e.g., peak power and oxygen uptake during an FES cycling test) (GRADE ratings: ‘Low’). Conclusion Current evidence indicates that FES cycling exercise improves lower-body muscle health of adults with SCI, and may increase power output and aerobic fitness. The evidence summarized and appraised in this review can inform the development of the first international, evidence-based clinical practice guidelines for the use of FES cycling exercise in clinical and community settings of adults with SCI. Registration review protocol : CRD42018108940 (PROSPERO)

The number of systematic reviews on the effects of exercise on aerobic fitness and muscle strength in people with spinal cord injury (SCI) has recently increased. However, the results of some of these reviews are inconclusive or inconsistent. To strengthen recommendations, this overview was undertaken to assimilate evidence about the effectiveness of different types of physical activities, exercises, and therapeutic interventions for improving aerobic fitness and muscle strength in people with SCI. Cochrane Overview of reviews methods were adopted to undertake this overview. An online search was conducted in August 2018 on eight databases based on predefined search criteria. Potential systematic reviews were screened, selected, and assessed on methodological quality by two independent authors, and discussed and resolved with a third author, when necessary. Only systematic reviews published in the English language were included. The protocol was registered on PROSPERO. Overall, 16 systematic reviews were included (aerobic fitness, n = 10; muscle strength, n = 15). For all 16 reviews, the quality of evidence was rated as “critically low.” Despite low evidence, this overview strengthens the existing guidelines for people with SCI, providing specific advice on exercise domains (types, intensities, frequency, and duration) for improving aerobic fitness and muscle strength. The evidence from this overview suggests that ergometry training with/without additional therapeutic interventions (20 min, moderate to vigorous intensity, twice weekly for 6 weeks) may improve aerobic fitness; similarly, resistance training with/without additional therapeutic interventions (three sets of 8–10 repetitions, moderate to vigorous intensity, twice weekly for 6 weeks) may improve muscle strength.

Objectives: This study described leisure-time physical activity (LTPA) for people in Australia with spinal cord injury (SCI) and whether certain sociodemographic and psychosocial variables might be associated with LTPA uptake and guidelines adherence. Methods: The Physical Activity Scale for Individuals with a Physical Disability was used to measure the intensity and volume of LTPA of 1,579 individuals with SCI. Summary statistics were calculated for LTPA guidelines adherence. Analyses included regression modelling. Results: Of the 1,579 participants, 58% performed LTPA and 13% adhered to recommended guidelines for weekly LTPA. There was an association with being an “exerciser” based on the time since injury (OR = 1.02 [95% 1.01–1.03]), a traumatic injury (OR = 1.53 [95% CI 1.13–2.08]) and a higher self-rating of health (OR = 1.10 [95% CI 0.95–1.27]). Where LTPA guidelines were met, adherence was most related to a traumatic injury (OR = 1.75 [95% CI 1.02–3.02]) and being unemployed (OR = 1.53 [95% CI 1.03–2.25]). Conclusion: Of those who performed LTPA with SCI, one in four met population-specific LTPA guidelines. Sociodemographic variables were moderately associated with being an “exerciser” or LTPA “guideline-adherent.”

Background Heart rate variability biofeedback (HRV-F) is a neurocardiac self-regulation therapy, that has been shown to improve cardiac autonomic regulation, emotional regulation, and cognitive function in various clinical populations. Despite this, there is little evidence for the benefit of HRV-F in adults with spinal cord injury (SCI). Methods This study evaluated the feasibility of conducting a parallel randomised controlled trial (RCT) to evaluate the effectiveness of a 10-week HRV-F intervention for adults with chronic SCI. Individuals with SCI (irrespective of level and completeness), at least 12 months after diagnosis due to any traumatic or non-traumatic and non-progressive cause, and aged between 18 and 70 years of age were eligible to participate. Feasibility was evaluated in terms of six primary outcomes: (i) randomisation and blinding, (ii) participant safety, (iii) recruitment, (iv) retention, (v) adherence to the intervention, and (vi) primary outcome data collection methods (heart rate variability [HRV] and cerebral blood velocity [CBv]). Participants’ satisfaction, impression of change, and technological issues were assessed as secondary outcomes. Results The first 10 participants of the RCT ( n  = 120) were studied in the 10-week feasibility study. No serious adverse events occurred during the study activities (assessment or intervention sessions). While there were no withdrawals and high adherence to the intervention, the recruitment rate was below the target. There were no missing HRV data; however, missing data for CBv was higher than anticipated based on the literature (35% vs. 20%). A few minor connectivity issues occurred with the technology used for home training by participants. Modifications to the RCT protocol, including adjusting the eligibility criteria, recalculating the sample size, conducting interventions in participants’ homes, and altering the CBv assessment protocol, were proposed to address these issues. Conclusions With the proposed modifications implemented, the RCT is deemed feasible for investigating the effectiveness of a 10-week HRV-F intervention for adults with chronic SCI. Trial registration Australian and New Zealand Clinical Trial Registry (ACTRN12621000870853). Registered on July 6, 2021.

The difficulty of real-time muscle force or joint torque estimation during neuromuscular electrical stimulation (NMES) in physical therapy and exercise science has motivated recent research interest in torque estimation from other muscle characteristics. This study investigated the accuracy of a computational intelligence technique for estimating NMES-evoked knee extension torque based on the Mechanomyographic signals (MMG) of contracting muscles that were recorded from eight healthy males. Simulation of the knee torque was modelled via Support Vector Regression (SVR) due to its good generalization ability in related fields. Inputs to the proposed model were MMG amplitude characteristics, the level of electrical stimulation or contraction intensity, and knee angle. Gaussian kernel function, as well as its optimal parameters were identified with the best performance measure and were applied as the SVR kernel function to build an effective knee torque estimation model. To train and test the model, the data were partitioned into training (70%) and testing (30%) subsets, respectively. The SVR estimation accuracy, based on the coefficient of determination (R2) between the actual and the estimated torque values was up to 94% and 89% during the training and testing cases, with root mean square errors (RMSE) of 9.48 and 12.95, respectively. The knee torque estimations obtained using SVR modelling agreed well with the experimental data from an isokinetic dynamometer. These findings support the realization of a closed-loop NMES system for functional tasks using MMG as the feedback signal source and an SVR algorithm for joint torque estimation.

Background: People with a Fontan circulation usually have moderately impaired exercise performance, although a subset have high physical performance (“Super-Fontan”), which may represent a low-risk phenotype. Methods: People with a “Super-Fontan” phenotype were defined as achieving normal exercise performance [≥80% predicted peak oxygen uptake (VO 2 ) and work rate] during cardiopulmonary exercise testing (CPET) and were identified from the Australian and New Zealand Fontan Registry. A Fontan control group that included people with impaired exercise performance (<80% predicted VO 2 or work rate) was also identified based on a 1:3 allocation ratio. A subset of participants were prospectively recruited and completed a series of physical activity, exercise self-efficacy, and health-related quality of life questionnaires. Results: Sixty CPETs (“Super-Fontan”, n = 15; control, n = 45) were included. A subset (“Super-Fontan”, n = 10; control, n = 13) completed a series of questionnaires. Average age was 29 ± 8 years; 48% were males. Exercise capacity reflected by percent predicted VO 2 was 67 ± 17% in the entire cohort. Compared to the “Super-Fontan” phenotype, age at Fontan completion was higher in controls (4.0 ± 2.9 vs. 7.2 ± 5.3 years, p = 0.002). Only one (7%) person in the “Super-Fontan” group had a dominant right ventricle compared to 15 (33%) controls ( p = 0.043). None of those in the “Super-Fontan” group were obese, while almost a quarter (22%) of controls were obese based on body mass index ( p = 0.046). Lung function abnormalities were less prevalent in the “Super-Fontan” group (20 vs. 70%, p = 0.006). Exercise self-efficacy was greater in the “Super-Fontan” group (34.2 ± 3.6 vs. 27.9 ± 7.2, p = 0.02). Self-reported sports participation and physical activity levels during childhood and early adulthood were higher in the “Super-Fontan” group ( p < 0.05). The total average time spent participating in structured sports and physical activity was 4.3 ± 2.6 h/wk in the “Super-Fontan” group compared to 2.0 ± 3.0 h/wk in controls, p = 0.003. There were no differences in self-reported current total physical activity score or health-related quality of life between groups ( p ≥ 0.05). Conclusions: The “Super-Fontan” phenotype is associated with a healthy weight, lower age at Fontan completion, better exercise self-efficacy, and higher overall levels of sport and physical activity participation during physical development.

Adults with spinal cord injury (SCI) are often sedentary, increasing their risk of cardiometabolic diseases. Leisure-time Physical Activity (LTPA) is physical activity completed during recreation time for enjoyment. We aimed to quantify LTPA in people ≥45 years with SCI and to explore its relationship with participants' characteristics. This is a secondary analysis on a subset of the Australian International SCI Survey in participants ≥45 years, at least 12 months post-injury. We described levels of LTPA and used multivariable regressions to estimate the associations between participant characteristics and LTPA. Of 1,281 participants (mean age: 62.7 years, mean time since injury: 18.7 years; 74% males) 44% reported no participation in LTPA. The average LTPA participation was 197 (SD 352) minutes per week (median: 50). Females (β = -62.3, 95% CI [-112.9, -11.7]), and participants with non-traumatic injuries (β = -105.2, 95% CI [-165.9, -44.6]) performed less LTPA. Time since injury was not associated with moderate-to-heavy LTPA (LR: Probability > F = 0.785). LTPA promotion in the SCI population ≥45 years focusing on females and non-traumatic injuries is warranted.

This study investigated indirect measures of post-exercise parasympathetic reactivation (using heart-rate-variability, HRV) and sympathetic withdrawal (using systolic-time-intervals, STI) following upper- and lower-body exercise. Randomized, counter-balanced, crossover. 13 males (age 26.4±4.7years) performed maximal arm-cranking (MAX-ARM) and leg-cycling (MAX-LEG). Subsequently, participants undertook separate 8-min bouts of submaximal HR-matched exercise of each mode (ARM and LEG). HRV (including natural-logarithm of root-mean-square-of-successive-differences, Ln-RMSSD) and STI (including pre-ejection-period, PEP) were assessed throughout 10-min seated recovery. Peak-HR was higher (p=0.001) during MAX-LEG (182±7beatsmin−1) compared with MAX-ARM (171±12beatsmin−1), while HR (p<0.001) and Ln-RMSSD (p=0.010) recovered more rapidly following MAX-ARM. PEP recovery was similar between maximal bouts (p=0.106). HR during submaximal exercise was 146±7 (LEG) and 144±8beatsmin−1 (LEG) (p=0.139). Recovery of HR and Ln-RMSSD was also similar between submaximal modalities, remaining below baseline throughout recovery (p<0.001). PEP was similar during submaximal exercise (LEG 70±6ms; ARM 72±9ms; p=0.471) although recovery was slower following ARM (p=0.021), with differences apparent from 1- to 10-min recovery (p≤0.036). By 10-min post-exercise, PEP recovered to baseline (132±21ms) following LEG (130±21ms; p=0.143), but not ARM (121±17ms; p=0.001). Compared with submaximal lower-body exercise, HR-matched upper-body exercise elicited a similar recovery of HR and HRV indices of parasympathetic reactivation, but delayed recovery of PEP (reflecting sympathetic withdrawal). Exercise modality appears to influence post-exercise parasympathetic reactivation and sympathetic withdrawal in an intensity-dependent manner. These results highlight the need for test standardization and may be relevant to multi-discipline athletes and in clinical applications with varying modes of exercise testing.

Background Spinal cord injury (SCI) is associated with autonomic imbalance and significant secondary conditions, including cardiac and brain dysfunction that adversely impact health and wellbeing. This study will investigate the effectiveness (intention-to-treat) of a neuro-cardiac self-regulation therapy to improve autonomic and neural/brain activity in adults with SCI living in the community. Methods A two-arm parallel, randomised controlled trial in which adults with SCI living in the community post-rehabilitation will be randomly assigned to a treatment or control group. The treatment group ( N  = 60) aged 18–70 years with a chronic traumatic or non-traumatic SCI, will receive intervention sessions once per week for 10 weeks, designed to regulate autonomic activity using computer-based feedback of heart rate variability and controlled breathing (called HRV-F). Comprehensive neurophysiological and psychological assessment will occur at baseline, immediate post-treatment, and 6 and 12-months post-treatment. Primary outcome measures include electrocardiography/heart rate variability (to assess autonomic nervous system function) and transcranial doppler sonography (to assess cerebral blood circulation in basal cerebral arteries). Secondary outcomes measures include continuous blood pressure, electroencephalography, functional near-infrared spectroscopy, respiration/breath rate, electrooculography, cognitive capacity, psychological status, pain, fatigue, sleep and quality of life. Controls ( N  = 60) will receive usual community care, reading material and a brief telephone call once per week for 10 weeks and be similarly assessed over the same time period as the HRV-F group. Linear mixed model analysis with repeated measures will determine effectiveness of HRV-F and latent class mixture modelling used to determine trajectories for primary and selected secondary outcomes of interest. Discussion Treatments for improving autonomic function after SCI are limited. It is therefore important to establish whether a neuro-cardiac self-regulation therapy can result in improved autonomic functioning post-SCI, as well as whether HRV-F is associated with better outcomes for secondary conditions such as cardiovascular health, cognitive capacity and mental health. Trial registration The study has been prospectively registered with the Australian and New Zealand Clinical Trial Registry ( ACTRN12621000870853 .aspx). Date of Registration: 6th July 2021. Trial Sponsor: The University of Sydney, NSW 2006. Protocol version: 22/07/2021.