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.

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.

A cross-sectional comparison between cardiorespiratory fitness, level of lesion and red blood cell distribution width in adults with chronic spinal cord injury.

OBJECTIVES: To assess; (1) differences in red blood cell distribution width between individuals with chronic (>1year), motor-complete cervical (n=21), upper-thoracic (n=27) and thoracolumbar (n=15) spinal cord injury and, (2) associations between red blood cell distribution width and cardiorespiratory fitness. DESIGN: Prospective multi-center, cross-sectional study. METHODS: Peak oxygen uptake was determined using an upper-body arm-crank exercise test to volitional exhaustion and red blood cell distribution width was measured using an automated hematology system. RESULTS: There were significant (p<0.009) differences between groups classified by level of injury in absolute and relative peak oxygen uptake, peak power output and red blood cell distribution width. A significant (p<0.001) large negative association (r = -0.524) was found between relative peak oxygen uptake and red blood cell distribution width. Unbiased recursive partitioning, while revealing study site specific differences in red blood cell distribution width, identified homogenous subgroups based specifically on cardiorespiratory fitness irrespective of additional demographic and injury characteristics. CONCLUSION: The strong negative association between cardiorespiratory fitness and red blood cell distribution width in individuals with paraplegia parallel those previously observed in non-disabled individuals. Higher red blood cell distribution width values are an independent risk factor for increased cardiovascular mortality, heart failure, and coronary heart disease and may reflect several underlying exacerbated metabolic responses such as oxidative stress and systemic inflammation. These data emphasize the importance of maintaining a high aerobic capacity following spinal cord injury.