Abstract
ABSTRACTBackgroundA low level of cardiorespiratory fitness [CRF; typically defined as peak oxygen uptake (V̇2peak) or peak power output (PPO)] is a widely reported consequence of spinal cord injury (SCI). This systematic review with meta-analysis and meta-regression aimed to assess whether certain SCI characteristics and specific exercise considerations are moderators of changes in CRF.MethodsEligible studies included randomised controlled trials (RCTs) and pre-post studies that conducted an exercise intervention lasting >2 weeks. The outcome measures of interest were absolute (AV̇O2peak) or relative V̇O2peak (RV̇O2peak), and/or PPO. Four databases were searched up to July 2021. The Cochrane Risk of Bias 2 tool and the National Institute of Health Quality Assessment Tool were used to assess bias/quality. The certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Random effects meta-analyses and meta-regressions were conducted.ResultsNinety studies (110 independent exercise interventions) with a total of 1,191 participants were included in our primary meta-analysis. There were significant improvements in AV̇O2peak [0.22 (0.17, 0.26) L/min, p<0.001)], RV̇O2peak [2.8 (2.2, 3.4) mL/kg/min, p<0.001)], and PPO [11 (8, 13) W, p<0.001]. There were no subgroup differences in AV̇O2peak or RV̇O2peak. There were subgroup differences (p≤0.008) for changes in PPO based on time since injury, neurological level of injury, exercise modality, relative exercise intensity, method of exercise intensity prescription, and frequency. The meta-regression found that increased age was associated with increases in AV̇O2peak and RV̇O2peak, and exercise intensity prescription and volume were associated with increases in PPO (p<0.05). GRADE assessments indicated a low level of certainty in the estimated effects due to study design, risk of bias, inconsistency, and imprecision.ConclusionThe pooled analysis indicates that performing exercise >2 weeks results in significant improvements in AV̇O2peak, RV̇O2peak and PPO in individuals with SCI. Subgroup comparisons identify that upper-body aerobic exercise and resistance training appear the most effective at improving PPO. Furthermore, acutely-injured, individuals with paraplegia, exercising at a moderate-to-vigorous intensity, prescribed via a percentage of oxygen consumption or heart rate, for more than 3 sessions/week will likely experience the greatest change in PPO.RegistrationPROSPERO CRD42018104342Key Points- Exercise interventions >2 weeks can significantly improve cardiorespiratory fitness in individuals with a spinal cord injury, by a magnitude greater than one spinal cord injury adjusted metabolic equivalent (i.e., ≥2.7 mL/kg/min). A one metabolic equivalent improvement has been associated with a reduction in cardiovascular related mortality risk in non-injured individuals.- Our findings support the minimum 40 minutes of weekly moderate-to-vigorous intensity exercise recommended by the spinal cord injury-specific exercise guidelines to significantly improve fitness. However, a two-fold greater improvement in peak power output may be achieved with exercising ≥90 min/week in comparison to ≥40 min/week.- Our secondary meta-analysis comparing cohort studies indicates that prolonged exercise participation benefits cardiorespiratory fitness in the long term. However, these studies are prone to confounding and are inherently biased.- Future research should consider following the recommendations published in the exercise intervention reporting guidelines, investigate the dose-response relationship between exercise and cardiorespiratory fitness in this population, and identify whether differences in supraspinal sympathetic cardiovascular impacts changes in cardiorespiratory fitness.
Publisher
Cold Spring Harbor Laboratory