Physical exercise training to increase cardiorespiratory fitness in people with spinal cord injury

RATIONALE: Cardiorespiratory fitness (CRF) is a key determinant of health, independence, and quality of life for people with spinal cord injury (SCI). It is therefore important to know whether, and to what extent, physical exercise training increases CRF in people with SCI. OBJECTIVES: To assess the short- (< 6 weeks) and long-term (> 6 weeks) effects (benefits and harms) of physical exercise training for improving CRF compared with no intervention in people with SCI. SEARCH METHODS: We searched CENTRAL, MEDLINE and three other databases to 9 December 2025, and six clinical trials registries. Our search combined terms for the health condition (SCI), the intervention (physical exercise training) and the study design (randomised controlled trials and randomised cross-over trials). ELIGIBILITY CRITERIA: We included studies that compared physical exercise training programmes to improve CRF with no intervention. The physical exercise training needed to be a planned and structured exercise programme that included specific recommendations for the type, intensity, frequency, and duration of the training, with the aim of increasing CRF. OUTCOMES: The critical outcomes were CRF, functional fitness, quality of life, depression and anxiety, and adverse events. Other outcomes included perceived exertion during exercise, independence, physical activity levels, fatigue, and sleep quality. RISK OF BIAS: We rated 96% of studies as being at high risk of bias for CRF using the Cochrane Risk of bias 2 tool (RoB 2). SYNTHESIS METHODS: We pooled data in meta-analyses using random-effects models, provided there were two or more studies without marked clinical or statistical heterogeneity. We conducted subgroup analyses to determine the effects of the duration of physical exercise training programmes (< 12 weeks versus ≥ 12 weeks), the frequency of physical exercise training (< 3 times a week versus ≥ 3 times a week) and the intensity of physical exercise training (light intensity versus moderate to vigorous intensity). We applied the GRADE approach to assess the certainty of evidence. INCLUDED STUDIES: We included 17 studies with a total of 505 participants. Only 15 studies (337 participants) provided data that we could use in one or more of the quantitative syntheses. Physical exercise training was provided via hand cycling, rowing, wheelchair propulsion, robotic gait training, walking/running and mixed gym equipment. Training was provided between two and five times per week for between six weeks and nine months. Each session lasted between 30 minutes and two hours. All studies examined the short-term effects of physical exercise training, and one study examined the long-term effects. SYNTHESIS OF RESULTS: = 2%; very low-certainty evidence) with the 95% CI spanning zero, indicating that it is very unclear whether physical exercise training increases quality of life. One study with 23 participants contributed data to a meta-analysis investigating the short-term effects of physical exercise training compared to no intervention on depression and anxiety. The mean difference (MD) was 9/60 points on the Centre for Epidemiological Studies Scale (95% CI -0.98 to 18.98; very low-certainty evidence), indicating that it is very unclear whether physical exercise training decreases depression and anxiety. Four studies with 141 participants reported data on adverse events, but only one study with 68 participants contributed data to a meta-analysis investigating the short-term effects of physical exercise training compared to no intervention on adverse events. The risk ratio (RR) was 1.30 (95% CI 0.32 to 5.26; very low-certainty evidence), indicating that it is very unclear whether physical exercise training increases adverse events. AUTHORS' CONCLUSIONS: The main finding from this review is that physical exercise training may increase CRF in people with SCI, but evidence certainty is low because of the potential for bias in the included studies. The effects of physical exercise training on other outcomes of interest in this review are very unclear. This includes: functional fitness, quality of life, depression and anxiety, adverse events, perceived exertion during exercise, independence, physical activity levels, fatigue, and sleep quality. The uncertainty mainly arises from the very small number of studies that included these outcomes. Among those studies, the risk of bias (as assessed by RoB 2) is high, and the estimates of the pooled treatment effects are often imprecise due to the small number of participants. Importantly, the estimates of the treatment effects span zero and neither rule in nor rule out a therapeutic effect from physical exercise training on any of these outcomes. FUNDING: There is no direct funding to declare for this systematic review, although LH's position is funded by SIRA and icare (government regulatory organisations responsible for compensation and insurance). REGISTRATION: Protocol (2024) DOI: 10.1002/14651858.CD014476.