Hey, there, not to take anything away from spankyNspronkle's solution (great guy, great solution), but I just managed to get this easily with another workout:
Gatorade Football Training Camp - Recovery featuring JJ Watt
The workout is 4 minutes long and there are only 4 drills in it. They're all stretching drills, so you can easily get 5 stars on them as long as your Kinect is picking you up (some portions of the drills have you very close to the ground). You just need to get 5 stars on at least 3 of the drills.
I'm actually not sure how long the workout will be available, but it can also help you get the following achievements very quickly:
The Aced! achievement in Xbox Fitness worth 239 pointsComplete all session challenges for one workout.
(although I was encountering a bug where my challenge was considered completed before I completed it, thus making Aced unobtainable with this workout)