A trumpeter is usually taught early on certain passages and routines for warming up, but is rarely told why it's good to warm up with this that or the other.
Much like an athlete, it's important for a trumpeter to warm up to prevent tension, set good air usage, help the fingers and tongue become flexible, and get everything to function optimally. Unfortunately, many warm ups cause more tension and strain than what they prevent. Improperly doing lip slurs, multiple octave scales, and other warm up activities, can cause more than what they cure.
My personal warm up consists of SOFT playing for several minutes (up to an hour) with my lips set closely together and using the corners in an inward kissing type motion. This prevents me from pulling the lips back in a smile formation - which causes the lips to thin and increase muscle tension vs. using air. My goal is to get the lips to buzz freely close together by using the air stream and holding the lips in the same position. Soft notes and high notes are very closely related!
If you'd like more information, please contact me at Brass Player Solution! I offer a course called "Back To Basics" for trumpeters! 4 weeks of 30 minute videos, and as an added bonus, a Q&A session each week scheduled to fit your scheduling needs.