This warmup I started on when I was 11 years old and I use it every morning. This is how I start warming up! The reason why I use this is because it condenses all of the scales within a short period of time while shiftly chromatically one octave at a time allowing me to work on fluidity and changing keys rapidly.
The document is in major scales but this can also be even more challenging by alternating between major and minor. This allows the musician an opportunity to not only work on the mechanics of playing the instrument but it also gives you a mental challenge so you are never playing “by rote” (playing without thinking). If you know your scales, this is no problem.
There are different levels you can take this exercise to. I like to apply this to my students depending on their level of study. We often do this in group sessions in a circle. Every student of mine will play alternating scales and we keep a circle going. It’s actually very fun!