Heart Rate Response
Drew explains the gradual heart rate increase during the first interval of a workout. He recommends starting interval training on a rowing machine for quick heart rate elevation and muscle engagement. Simon prefers using a rowing machine over a stationary bike for easier heart rate control.In this clip
From this podcast

The Proof with Simon Hill
Zone 2 takeaways and an evidence-based 3 day cardio program for longevity | Drew Harrisberg, BSc
Related Questions
How high should the heart rate go during high-intensity cycling intervals?
Please clarify how to achieve the heart rates in the HIIT protocol: "4 intervals alternating between 4 minutes at 85–95% of maximal heart rate and 3 minutes at 60–70%." It seems impossible to immediately transition from 70% MHR to 85-95%, and vice versa.