When speaking of a “burn” we are talking about the warming sensation in our embouchure muscles which happens when we start to overdo work on our lips.
Knowing when to stop when experiencing a burn is very important for overdoing can lead to damage to your lip.
This exercise makes use of very short intervals of actual playing which will make sure that the player is not exceeding beneficial limits to his/her lips.
Listen to the recording and repeat the same notes. With this listen- repeat format, you should not get too tired and still work your embouchure.