Training responsiveness of cardiorespiratory fitness and arterial stiffness following moderate-intensity continuous training and high-intensity interval training in adults with intellectual and developmental disabilities

Background: Cardiorespiratory fitness (CRF) prompts antiatherogenic adaptations in vascular function and structure. However, there is an extraordinary interindividual variability in response to a standard dose of exercise, wherein a substantial number of adults with intellectual and developmental disabilities (IDD) do not improve CRF. We (1) evaluated the effects of 12-month of moderate-intensity continuous training (MICT) on CRF and arterial stiffness and (2) tested whether an additional 3-month of high-intensity interval training (HIIT) would add to improvements in CRF responsiveness and arterial stiffness. Methods: Fifteen adults with mild-to-moderate IDD (male adults = 9, 30.1 ± 7.5 years old) met 3 days per week for 30 min MICT for 12 months, after which the incidence of CRF responsiveness was calculated (≥5.0% change in absolute peak VO₂). Thereafter, responders and non-responders started HIIT for 3 months with identical daily training load/frequency. Peak VO₂, local and regional indices of arterial stiffness were assessed prior to and after each period. Results: Sixty per cent of the participants were non-responders following MICT, but the incidence dropped to 20% following HIIT (P = 0.03). Absolute peak VO₂ values reached significant difference from pre-intervention (+0.38 ± 0.08 L min⁻¹, P = 0.001) only when HIIT was added. Lower limb pulse wave velocity (PWV) decreased following MICT (−0.8 ± 1.1 m s⁻¹, P = 0.049), whereas central PWV only decreased following HIIT (−0.8 ± 0.9 m s⁻¹, P = 0.013). Conclusions: Cardiorespiratory fitness responsiveness and reductions in PWV to a 12-month MICT period in adults with IDD improved following a period of HIIT programme inducing higher metabolic stress.