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

Abstract

Cohort study. To investigate and critique different methods for aerobic exercise intensity prescription in adults with spinal cord injury (SCI). University laboratory in Loughborough, UK. 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 (V̇O₂), 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-V̇O₂ plotted against log-[BLa] (LT₁) and 1.5 mmol L^-1 greater than LT₁ (LT₂). These were used to demarcate moderate (<LT₁), heavy (>LT₁, < LT₂) and severe (>LT₂) exercise intensity domains. 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 %V̇O_2peak and %HR_peak at lactate thresholds resulted in large variability in the domain distribution at fixed %V̇O_2peak and %HR_peak. Fixed %V̇O_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.