Neuromuscular electrical stimulation resistance training enhances oxygen uptake and ventilatory efficiency independent of mitochondrial complexes after spinal cord injury: a randomized clinical trial

Trends in measuring BMR and RMR after spinal cord injury: a comprehensive review

Studying factors that contribute to our understanding of maintaining normal energy balance are of paramount significance following spinal cord injury (SCI). Accurate determination of energy needs is crucial for providing nutritional guidance and managing the increasing prevalence of malnutrition or obesity after SCI. BMR represents 75-80 % of the total energy expenditure in persons with SCI. Accurately measuring BMR is an important component for calculating total energetic needs in this population. Indirect calorimetry is considered the gold-standard technique for measuring BMR. However, technical challenges may limit its applications in large cohort studies and alternatively rely on prediction equations. Previous work has shown that BMR changes in response to disuse and exercise in the range of 15-120 %. Factors including sex, level of injury and type of assistive devices may influence BMR after SCI. RMR is erroneously used interchangeably for BMR, which may result in overestimation of energetic intake when developing nutritional plans. To address this concern, we comprehensively reviewed studies that conducted BMR (n=15) and RMR (n=22) in persons with SCI. The results indicated that RMR is 9 % greater than BMR in persons with SCI. Furthermore, the SCI-specific prediction equations that incorporated measures of fat-free mass appeared to accurately predict BMR. Overall, the current findings highlighted the significance of measuring BMR as well as encouraging the research and clinical community to effectively establish countermeasures to combat obesity after SCI.

Exercise and aerobic capacity in individuals with spinal cord injury: A systematic review with meta-analysis and meta-regression

BACKGROUND

A low level of cardiorespiratory fitness [CRF; defined as peak oxygen uptake ([Formula: see text]O2peak) or peak power output (PPO)] is a widely reported consequence of spinal cord injury (SCI) and a major risk factor associated with chronic disease. However, CRF can be modified by exercise. This systematic review with meta-analysis and meta-regression aimed to assess whether certain SCI characteristics and/or specific exercise considerations are moderators of changes in CRF.

METHODS AND FINDINGS

Databases (MEDLINE, EMBASE, CENTRAL, and Web of Science) were searched from inception to March 2023. A primary meta-analysis was conducted including randomised controlled trials (RCTs; exercise interventions lasting >2 weeks relative to control groups). A secondary meta-analysis pooled independent exercise interventions >2 weeks from longitudinal pre-post and RCT studies to explore whether subgroup differences in injury characteristics and/or exercise intervention parameters explained CRF changes. Further analyses included cohort, cross-sectional, and observational study designs. Outcome measures of interest were absolute (A[Formula: see text]O2peak) or relative [Formula: see text]O2peak (R[Formula: see text]O2peak), and/or PPO. Bias/quality was assessed via The Cochrane Risk of Bias 2 and the National Institute of Health Quality Assessment Tools. Certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Random effects models were used in all meta-analyses and meta-regressions. Of 21,020 identified records, 120 studies comprising 29 RCTs, 67 pre-post studies, 11 cohort, 7 cross-sectional, and 6 observational studies were included. The primary meta-analysis revealed significant improvements in A[Formula: see text]O2peak [0.16 (0.07, 0.25) L/min], R[Formula: see text]O2peak [2.9 (1.8, 3.9) mL/kg/min], and PPO [9 (5, 14) W] with exercise, relative to controls (p < 0.001). Ninety-six studies (117 independent exercise interventions comprising 1,331 adults with SCI) were included in the secondary, pooled meta-analysis which demonstrated significant increases in A[Formula: see text]O2peak [0.22 (0.17, 0.26) L/min], R[Formula: see text]O2peak [2.8 (2.2, 3.3) mL/kg/min], and PPO [11 (9, 13) W] (p < 0.001) following exercise interventions. There were subgroup differences for R[Formula: see text]O2peak based on exercise modality (p = 0.002) and intervention length (p = 0.01), but there were no differences for A[Formula: see text]O2peak. There were subgroup differences (p ≤ 0.018) for PPO based on time since injury, neurological level of injury, exercise modality, and frequency. The meta-regression found that studies with a higher mean age of participants were associated with smaller changes in A[Formula: see text]O2peak and R[Formula: see text]O2peak (p < 0.10). GRADE indicated a moderate level of certainty in the estimated effect for R[Formula: see text]O2peak, but low levels for A[Formula: see text]O2peak and PPO. This review may be limited by the small number of RCTs, which prevented a subgroup analysis within this specific study design.

CONCLUSIONS

Our primary meta-analysis confirms that performing exercise >2 weeks results in significant improvements to A[Formula: see text]O2peak, R[Formula: see text]O2peak, and PPO in individuals with SCI. The pooled meta-analysis subgroup comparisons identified that exercise interventions lasting up to 12 weeks yield the greatest change in R[Formula: see text]O2peak. Upper-body aerobic exercise and resistance training also appear the most effective at improving R[Formula: see text]O2peak and PPO. Furthermore, acutely injured, individuals with paraplegia, exercising for ≥3 sessions/week will likely experience the greatest change in PPO. Ageing seemingly diminishes the adaptive CRF responses to exercise training in individuals with SCI.

REGISTRATION

PROSPERO: CRD42018104342.

Effects of two different paradigms of electrical stimulation exercise on cardio-metabolic risk factors after spinal cord injury. A randomized clinical trial

Objective

To examine the combined effects of neuromuscular electrical stimulation-resistance training (NMES-RT) and functional electrical stimulation-lower extremity cycling (FES-LEC) compared to passive movement training (PMT) and FES-LEC in adults with SCI on (1) oxygen uptake (VO2), insulin sensitivity and glucose disposal in adults with SCI; (2) Metabolic and inflammatory biomarkers; (3) skeletal muscle, intramuscular fat (IMF) and visceral adipose tissue (VAT) cross-sectional areas (CSAs).

Materials and methods

Thirty-three participants with chronic SCI (AIS A-C) were randomized to 24 weeks of NMES-RT + FES or PMT + FES. The NMES-RT + FES group underwent 12 weeks of evoked surface NMES-RT using ankle weights followed by an additional 12 weeks of progressive FES-LEC. The control group, PMT + FES performed 12 weeks of passive leg extension movements followed by an additional 12 weeks of FES-LEC. Measurements were performed at baseline (BL; week 0), post-intervention 1 (P1; week 13) and post-intervention 2 (P2; week 25) and included FES-VO2 measurements, insulin sensitivity and glucose effectiveness using the intravenous glucose tolerance test; anthropometrics and whole and regional body composition assessment using dual energy x-ray absorptiometry (DXA) and magnetic resonance imaging to measure muscle, IMF and VAT CSAs.

Results

Twenty-seven participants completed both phases of the study. NMES-RT + FES group showed a trend of a greater VO2 peak in P1 [p = 0.08; but not in P2 (p = 0.25)] compared to PMT + FES. There was a time effect of both groups in leg VO2 peak. Neither intervention elicited significant changes in insulin, glucose, or inflammatory biomarkers. There were modest changes in leg lean mass following PMT + FES group. Robust hypertrophy of whole thigh muscle CSA, absolute thigh muscle CSA and knee extensor CSA were noted in the NMES-RT + FES group compared to PMT + FES at P1. PMT + FES resulted in muscle hypertrophy at P2. NMES-RT + FES resulted in a decrease in total VAT CSA at P1.

Conclusion

NMES-RT yielded a greater peak leg VO2 and decrease in total VAT compared to PMT. The addition of 12 weeks of FES-LEC in both groups modestly impacted leg VO2 peak. The addition of FES-LEC to NMES-RT did not yield additional increases in muscle CSA, suggesting a ceiling effect on signaling pathways following NMES-RT.

Clinical trial registration

identifier NCT02660073.

Spinal cord injury: molecular mechanisms and therapeutic interventions

Spinal cord injury (SCI) remains a severe condition with an extremely high disability rate. The challenges of SCI repair include its complex pathological mechanisms and the difficulties of neural regeneration in the central nervous system. In the past few decades, researchers have attempted to completely elucidate the pathological mechanism of SCI and identify effective strategies to promote axon regeneration and neural circuit remodeling, but the results have not been ideal. Recently, new pathological mechanisms of SCI, especially the interactions between immune and neural cell responses, have been revealed by single-cell sequencing and spatial transcriptome analysis. With the development of bioactive materials and stem cells, more attention has been focused on forming intermediate neural networks to promote neural regeneration and neural circuit reconstruction than on promoting axonal regeneration in the corticospinal tract. Furthermore, technologies to control physical parameters such as electricity, magnetism and ultrasound have been constantly innovated and applied in neural cell fate regulation. Among these advanced novel strategies and technologies, stem cell therapy, biomaterial transplantation, and electromagnetic stimulation have entered into the stage of clinical trials, and some of them have already been applied in clinical treatment. In this review, we outline the overall epidemiology and pathophysiology of SCI, expound on the latest research progress related to neural regeneration and circuit reconstruction in detail, and propose future directions for SCI repair and clinical applications.

Electrical Stimulation Exercise for People with Spinal Cord Injury: A Healthcare Provider Perspective

Electrical stimulation exercise has become an important modality to help improve the mobility and health of individuals with spinal cord injury (SCI). Electrical stimulation is used to stimulate peripheral nerves in the extremities to assist with muscle strengthening or functional activities such as cycling, rowing, and walking. Electrical stimulation of the peripheral nerves in the upper extremities has become a valuable tool for predicting the risk of hand deformities and rehabilitating functional grasping activities. The purpose of this paper is to provide healthcare providers perspective regarding the many rehabilitation uses of electrical stimulation in diagnosing and treating individuals with SCI. Electrical stimulation has been shown to improve functional mobility and overall health, decrease spasticity, decrease the risk of cardiometabolic conditions associated with inactivity, and assist in the diagnosis/prognosis of hand deformities in those with tetraplegia. Studies involving non-invasive stimulation of the spinal nerves via external electrodes aligned with the spinal cord and more invasive stimulation of electrodes implanted in the epidural lining of the spinal cord have demonstrated improvements in the ability to stand and enhanced the stepping pattern during ambulation. Evidence is also available to educate healthcare professionals in using functional electrical stimulation to reduce muscle spasticity and to recognize limitations and barriers to exercise compliance in those with SCI. Further investigation is required to optimize the dose-response relationship between electrical stimulation activities and the mobility and healthcare goals of those with SCI and their healthcare providers.

Predictors of muscle hypertrophy responsiveness to electrically evoked resistance training after spinal cord injury

The purpose of the study was to identify potential predictors of muscle hypertrophy responsiveness following neuromuscular electrical stimulation resistance training (NMES-RT) in persons with chronic spinal cord injury (SCI). Data for twenty individuals with motor complete SCI who completed twice weekly NMES-RT lasting 12-16 weeks as part of their participation in one of two separate clinical trials were pooled and retrospectively analyzed. Magnetic resonance imaging (MRI) was used to measure muscle cross-sectional area (CSA) of the whole thigh and knee extensor muscle before and after NMES-RT. Muscle biopsies and fasting biomarkers were also measured. Following the completion of the respective NMES-RT trials, participants were classified into either high-responders (n = 8; muscle CSA > 20%) or low-responders (n = 12; muscle CSA < 20%) based on whole thigh muscle CSA hypertrophy. Whole thigh muscle and knee extensors CSAs were significantly greater (P < 0.0001) in high-responders (29 ± 7% and 47 ± 15%, respectively) compared to low-responders (12 ± 3% and 19 ± 6%, respectively). There were no differences in total caloric intake or macronutrient intake between groups. Extensor spasticity was lower in the high-responders compared to the low-responders as was the dosage of baclofen. Prior to the intervention, the high-responders had greater body mass compared to the low-responders with SCI (87.8 ± 13.7 vs. 70.4 ± 15.8 kg; P = 0.012), body mass index (BMI: 27.6 ± 2.7 vs. 22.9 ± 6.0 kg/m2; P = 0.04), as well as greater percentage in whole body and regional fat mass (P < 0.05). Furthermore, high-responders had a 69% greater increase (P = 0.086) in total Akt protein expression than low-responders. High-responders also exhibited reduced circulating IGF-1 with a concomitant increase in IGFBP-3. Exploratory analyses revealed upregulation of mRNAs for muscle hypertrophy markers [IRS-1, Akt, mTOR] and downregulation of protein degradation markers [myostatin, MurF-1, and PDK4] in the high-responders compared to low-responders. The findings indicate that body composition, spasticity, baclofen usage, and multiple signaling pathways (anabolic and catabolic) are involved in the differential muscle hypertrophy response to NMES-RT in persons with chronic SCI.

Testosterone and long pulse width stimulation (TLPS) for denervated muscles after spinal cord injury: a study protocol of randomised clinical trial

INTRODUCTION

Long pulse width stimulation (LPWS; 120-150 ms) has the potential to stimulate denervated muscles and to restore muscle size in denervated people with spinal cord injury (SCI). We will determine if testosterone treatment (TT)+LPWS would increase skeletal muscle size, leg lean mass and improve overall metabolic health in persons with SCI with denervation. We hypothesise that the 1-year TT+LPWS will upregulate protein synthesis pathways, downregulate protein degradation pathways and increase overall mitochondrial health.

METHODS AND ANALYSIS

Twenty-four male participants (aged 18-70 years with chronic SCI) with denervation of both knee extensor muscles and tolerance to the LPWS paradigm will be randomised into either TT+neuromuscular electrical stimulation via telehealth or TT+LPWS. The training sessions will be twice weekly for 1 year. Measurements will be conducted 1 week prior training (baseline; week 0), 6 months following training (postintervention 1) and 1 week after the end of 1 year of training (postintervention 2). Measurements will include body composition assessment using anthropometry, dual X-ray absorptiometry and MRI to measure size of different muscle groups. Metabolic profile will include measuring of basal metabolic rate, followed by blood drawn to measure fasting biomarkers similar to hemoglobin A1c, lipid panels, C reactive protein, interleukin-6 and free fatty acids and then intravenous glucose tolerance test to test for insulin sensitivity and glucose effectiveness. Finally, muscle biopsy will be captured to measure protein expression and intracellular signalling; and mitochondrial electron transport chain function. The participants will fill out 3 days dietary record to monitor their energy intake on a weekly basis.

ETHICS AND DISSEMINATION

The study was approved by Institutional Review Board of the McGuire Research Institute (ID # 02189). Dissemination plans will include the Veteran Health Administration and its practitioners, the national SCI/D services office, the general healthcare community and the veteran population, as well as the entire SCI community via submitting quarterly letters or peer-review articles.

TRIAL REGISTRATION NUMBER

NCT03345576.

Assessment of mitochondrial respiratory capacity using minimally invasive and noninvasive techniques in persons with spinal cord injury

Purpose

Muscle biopsies are the gold standard to assess mitochondrial respiration; however, biopsies are not always a feasible approach in persons with spinal cord injury (SCI). Peripheral blood mononuclear cells (PBMCs) and near-infrared spectroscopy (NIRS) may alternatively be predictive of mitochondrial respiration. The purpose of the study was to evaluate whether mitochondrial respiration of PBMCs and NIRS are predictive of respiration of permeabilized muscle fibers after SCI.

Methods

Twenty-two individuals with chronic complete and incomplete motor SCI between 18–65 years old were recruited to participate in the current trial. Using high-resolution respirometry, mitochondrial respiratory capacity was measured for PBMCs and muscle fibers of the vastus lateralis oxidizing complex I, II, and IV substrates. NIRS was used to assess mitochondrial capacity of the vastus lateralis with serial cuff occlusions and electrical stimulation.

Results

Positive relationships were observed between PBMC and permeabilized muscle fibers for mitochondrial complex IV (r = 0.86, P < 0.0001). Bland-Altman displayed agreement for complex IV (MD = 0.18, LOA = -0.86 to 1.21), between PBMCs and permeabilized muscles fibers. No significant relationships were observed between NIRS mitochondrial capacity and respiration in permeabilized muscle fibers.

Conclusions

This is the first study to explore and support the agreement of less invasive clinical techniques for assessing mitochondrial respiratory capacity in individuals with SCI. The findings will assist in the application of PBMCs as a viable alternative for assessing mitochondrial health in persons with SCI in future clinical studies.

Exoskeleton Training and Trans-Spinal Stimulation for Physical Activity Enhancement After Spinal Cord Injury (EXTra-SCI): An Exploratory Study

After spinal cord injury (SCI) physical activity levels decrease drastically, leading to numerous secondary health complications. Exoskeleton-assisted walking (EAW) may be one way to improve physical activity for adults with SCI and potentially alleviate secondary health complications. The effects of EAW may be limited, however, since exoskeletons induce passive movement for users who cannot volitionally contribute to walking. Trans-spinal stimulation (TSS) has shown the potential to enable those with even the most severe SCI to actively contribute to movements during EAW. To explore the effects of EAW training on improving secondary health complications in persons with SCI, participants with chronic (n = 8) were enrolled in an EAW program 2-3 times per week for 12 weeks. Anthropometrics (seated and supine waist and abdominal circumferences (WC and AC), body composition assessment (dual exposure x-ray absorptiometry-derived body fat percent, lean mass and total mass for the total body, legs, and trunk), and peak oxygen consumption (VO2 during a 6-minute walk test [6MWT]) were assessed before and after 12 weeks of EAW training. A subset of participants (n = 3) completed EAW training with concurrent TSS, and neuromuscular activity of locomotor muscles was assessed during a 10-m walk test (10MWT) with and without TSS following 12 weeks of EAW training. Upon completion of 12 weeks of training, reductions from baseline (BL) were found in seated WC (-2.2%, P = 0.036), seated AC (-2.9%, P = 0.05), and supine AC (-3.9%, P = 0.017). Percent fat was also reduced from BL for the total body (-1.4%, P = 0.018), leg (-1.3%, P = 0.018), and trunk (-2%, P = 0.036) regions. No effects were found for peak VO2. The addition of TSS for three individuals yielded individualized responses but generally increased knee extensor activity during EAW. Two of three participants who received TSS were also able to initiate more steps without additional assistance from the exoskeleton during a 10MWT. In summary, 12 weeks of EAW training significantly attenuated markers of obesity relevant to cardiometabolic health in eight men with chronic SCI. Changes in VO2 and neuromuscular activity with vs. without TSS were highly individualized and yielded no overall group effects.