Follow one of the warm up sequences in our library
As many reps as possible: Squat Jumps
As fast as possible:
30 Air Squats
30 Ground to Jump and Touch
The idea here is to complete as many squat jumps in a row as you can. Upon stopping, the objective is then to complete 30 air squats and 30 ground to jump and touch as quickly as possible. Upon finishing those 60 reps, give yourself a quick break, shake out your legs, and then when you feel ready start back over.