Background A low level of cardiorespiratory fitness [CRF; typically defined as peak oxygen uptake (VO2peak) 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.
Methods Eligible 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 (AVO2peak) or relative VO2peak (RVO2peak), 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.
Results Ninety studies (110 independent exercise interventions) with a total of 1,191 participants were included in our primary meta-analysis. There were significant improvements in AVO2peak [0.22 (0.17, 0.26) L/min, p<0.001)], RVO2peak [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 AVO2peak or RVO2peak. 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 AVO2peak and RVO2peak, 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.
Conclusion The pooled analysis indicates that performing exercise >2 weeks results in significant improvements in AVO2peak, RVO2peak 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.
Registration PROSPERO CRD42018104342