Abstract 10641: Changes in Oxygen Uptake Parameters Across High-Intensity Intervals Prescribed Using Rating of Perceived Exertion in Cardiac Rehabilitation

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Introduction: High intensity interval training (HIIT) during early outpatient cardiac rehabilitation (CR) improves peak oxygen uptake (VO 2 ) and reduces mortality in patients with cardiovascular disease. In a CR setting, prescribing interval intensity using rating of perceived exertion (RPE) is more feasible than using percent of VO 2peak . Additionally, prescribing HIIT with RPE may allow for progressive changes in the VO 2 response throughout a single HIIT session. However, the acute cardiopulmonary responses during individual intervals of HIIT prescribed via RPE in CR are unknown. Hypothesis: We hypothesized that VO 2peak would increase and time-to-peak (TTP) would shorten across high-intensity intervals during a single HITT session prescribed with RPE. Methods: Patients with CAD (N=14; 2 women; 56±9 yrs; 30.46±4.7 kg/m 2 ) referred to CR after an acute coronary event completed a minimum of 25 supervised HIIT sessions during which VO 2 was measured continuously. Each HIIT session included 5 or more (6±1 sessions) 1-minute high intensity intervals (target RPE: 15-17) separated by a 3 to 5-minute low intensity interval (target RPE: <12). The first and last HIIT sessions were used for analysis. VO 2peak was defined as the highest 3-breath averaged VO 2 during or up to 1 minute following each high intensity interval. Results: RPE was 15±2 and 11±2 during the high and low intensity intervals, respectively. Compared to the first HIIT session, VO 2peak was greater during the high intensity intervals of the last HIIT session (25.4±1.5 vs. 21.8±1.1 mL/kg/min; p=0.04). During the first and last HIIT sessions, VO 2peak increased across high intensity intervals (p<0.001). Although TTP was not significantly reduced across intervals during the first HIIT session (p=0.14), TTP was reduced across intervals during the last HIIT session (first interval: 67±19 vs. last interval: 58±9 s; p<0.01). Conclusions: Prescribing HIIT with RPE resulted in increased VO 2peak across high intensity intervals within single HIIT sessions and shortened TTP during high intensity intervals across CR. These findings provide evidence for a priming effect on VO 2peak during HIIT which may contribute to greater cardiopulmonary adaptations in CAD patients.