Rethinking aerobic exercise intensity prescription in adults with spinal cord injury: time to end the use of "moderate to vigorous" intensity?

STUDY DESIGN: Cohort study. OBJECTIVES: To investigate and critique different methods for aerobic exercise intensity prescription in adults with spinal cord injury (SCI). SETTING: University laboratory in Loughborough, UK. METHODS: Trained athletes were split into those with paraplegia (PARA; n=47), tetraplegia (TETRA; n=20) or alternate health condition (NON-SCI; n=67). Participants completed a submaximal step test with 3 min stages, followed by a graded exercise test to exhaustion in handcycling, arm crank ergometry or wheelchair propulsion. Oxygen uptake (VO2), heart rate (HR), blood lactate concentration ([BLa]) and ratings of perceived exertion (RPE) were measured. Lactate thresholds were identified as LT1 (intersection of log-VO2 vs log-[BLa]) and LT2 (1.5 mmol·L−1 above LT1) to demarcate moderate (<LT1), heavy (between LT1 and LT2) and severe (>LT2) domains. RESULTS: Associations between %VO2peak and %HRpeak with RPE differed between PARA and TETRA. At LT1 and LT2, %VO2peak and %HRpeak were significantly greater in TETRA than PARA and NON-SCI (P<0.05). Variability in %VO2peak and %HRpeak at lactate thresholds produced large variability in domain distribution at fixed %VO2peak and %HRpeak. CONCLUSIONS: Fixed %VO2peak and %HRpeak should not be used for aerobic exercise intensity prescription in adults with SCI as they do not yield uniform domain-specific intensity.