Interval training was designed to increase exercise intensity while reducing bodily demands like acid production and heart rate elevation.

“the interal training was designed to increase the intensity of EXC size while reducing the demands on the body so if you look at the works of work of uh Fox and Edwards uh their uh pioneers of internal training in United States they give some great examples so let's say you're running for 30 seconds and you're at this speed and you're going to produce this much acid and your heart rate is going to be this High well if you run for 10 seconds with short periods in between at the same speed you're going to produce a lot less acid and your heart rate is not going to climb to the stratosphere here”