Usually when I run intervals on the treadmill I warm up for a few minutes and then set the machine to my desired speed and begin training. Between intervals I stop completely jumping off to the sides to rest while the machine is still running and then after my desired rest period I jump back on.
The other week while I was doing this, someone in the gym came over to tell me that what I was doing is very dangerous, because making sudden stop while your heart rate is up is unhealthy. Now I understand that what he is saying is mostly true as I know that at the end of a cardio workout, cooling down is advisable in order to bring the heart rate down slowly.
Why doesn't the same rule apply to football players? They only run for a few seconds at a time at full intensity bringing their heart rates very high only to come to a sudden stop at the end of the play. That was my logic when I was stopping suddenly for a few seconds to catch my breath in preparation for my next sprint. Is what I'm doing really dangerous or is it ok for me to continue running intervals in this manner?