The more and longer intervals you train here will improve your conditioning and endurance. You might start out with four minute intervals with four minutes of
rest or however long it takes to recover four times. As your fitness improves you
can do longer and or more frequent intervals. Recovery is done below LT. I started
out training as hard as I could go but I did not see fast improvement until I learned
that base training below LT was needed for the next step up.