Cardiorespiratory fitness in individuals with spinal cord injury: the relationship with motor completeness

Objective: To compare cardiorespiratory fitness (CRF) in individuals with motor-complete spinal cord injury (SCI) with those with motor-incomplete SCI, while accounting for lesion level (“high” vs “low”). We hypothesized that individuals with motor-incomplete injuries would demonstrate higher CRF levels than those with motor-complete injuries, regardless of lesion level. Design: Retrospective multicenter cohort study. Setting: Dutch rehabilitation centers (N=12) involved in training participants for the HandbikeBattle event. Participants: A total of N=217 individuals with SCI and a history of rehabilitation who participated in the HandbikeBattle event between 2013 and 2023 (excluding 2020-2022 due to the coronavirus disease 2019 pandemic) were included. The final analysis included 202 participants. Interventions: Not applicable. Main Outcome Measures: Indicators of CRF were peak oxygen uptake (Vo₂peak) and peak power output (PPO), assessed during a cardiopulmonary exercise test on an arm ergometer. Results: Multilevel regression analyses showed that motor completeness of the lesion was not associated with either the relative or absolute values of Vo₂peak and PPO. Lesion level was associated with both Vo₂peak and PPO (relative and absolute), indicating that individuals with lower lesion levels had higher CRF outcomes than those with higher lesion levels. Conclusions: CRF is not determined by the motor completeness of the lesion, but rather by the neurological level of injury. These findings indicate that CRF should be addressed in individuals with both motor-complete and motor-incomplete SCI. Exercise intensity and progression should be tailored to the individual's neurological level and functional capacity to optimize training adaptations. This knowledge may improve the clinical interpretation of fitness assessments and support more personalized exercise interventions for the SCI population.