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 graded exercise test to exhaustion. Handcycling, arm crank ergometry or wheelchair propulsion were performed depending on the sport of the participant. Oxygen uptake (V̇ O₂), heart rate (HR), blood lactate concentration ([BLa]) and ratings of perceived exertion (RPE) on Borg’s RPE scale were measured throughout. Lactate thresholds were identified according to log-V̇ O₂ plotted against log-[BLa] (LT₁) and 1.5 mmol·L^-1 greater than LT₁ (LT₂). These were used to demarcate moderate (1), heavy (>LT₁, 2) and severe (>LT₂) exercise intensity domains
Results: Associations between percentage of peak V̇O₂ (%V̇O_2peak) and HR (%HR_peak) with RPE differed between PARA and TETRA. At LT₁ and LT₂, %V̇O_2peak and %HR_peak were significantly greater in TETRA compared to PARA and NON-SCI (P< 0.05). The variation in %V̇ O_2peak and %HR_peak at lactate thresholds resulted in large variability in the domain distribution at fixed %V̇ O_2peak and %HR_peak.
Conclusions: Fixed %V̇ O_2peak and %HR_peak should not be used for aerobic exercise intensity prescription in adults with SCI as the method does not lead to uniform exercise intensity domain distribution.