HIIT GuideNeed variety with your HIIT cardio workout routine? Enjoy over 60 variations of bike and treadmill workouts designed for 15, 30, and 45 minute workout intervals. These workouts are great to keep you mentally focused, prevent boredom, and to blast fat loss to the next level for those of you who are serious about getting results. Any of these workouts can be used to substitute any cardio workout in your custom training program or body type training