Acute physiological responses to high-intensity interval exercise in patients with coronary artery disease

Purpose Time spent closer to maximal effort during exercise is a potent stimulus for cardiorespiratory adaptations. The primary purpose was to determine which high-intensity interval exercise (HIIE) protocol provided the greatest physiological stimulus by comparing time spent ≥ 90% peak oxygen consumption (V̇O 2 peak) and heart rate reserve (HRR) in patients with coronary artery disease (CAD) in response to 3 HIIE protocols and the exercise standard of care, moderate-intensity continuous exercise (MICE). A secondary purpose was to assess protocol preference. Methods Fifteen patients with CAD (6 females, 67 ± 6 years) underwent measurements of V̇O 2 and heart rate during MICE and three HIIE protocols all performed on a treadmill. The HIIE protocols included one with long intervals (4 × 4-min), short intervals (10 × 1-min), and an adapted version of the 4 × 4 [Toronto Rehabilitation Institute Protocol, (TRIP)]. Time spent ≥ 90% V̇O 2 peak and HRR were compared. Results Time spent ≥ 90% V̇O 2 peak was higher during 4 × 4 (6.3 ± 8.4 min) vs. MICE (1.7 ± 3.9 min; P = 0.001), while time spent ≥ 90% HRR was higher during 4 × 4 (6.0 ± 5.3 min) vs. MICE (0.1 ± 0.2 min; P