Participation in this or any program is voluntary. Consult your doctor prior to beginning an exercise program or making changes to your lifestyle or health care routine. Grab a timer and hit this HIIT workout. After a brief warm up, perform each exercise for 30 seconds resting 15 seconds between exercises and up to 3 minutes between rounds. Aim for as many rounds as you can complete in 20 minutes. To decrease intensity, increase rest time. To increase intensity reduce rest time. Cool down with some flexibility exercises.