In these shorter Les Mills approved formats, you will still warm-up, work your legs, chest, back and abs. These muscle groups are key to the maintenance of posture, overall tone, and functional strength. The “Express” option is perfect if you are: 1) New to exercise and need to build up your endurance. 2) Short on time and only have 30 minutes to commit. 3) In need of a short strength/endurance session to combine with another cardio class/workout.