Routine boosters can make cardio even more fun and effective than it was in the first place. Sure, walking for 30 minutes per day is healthy, but it can begin to feel too easy and repetitive before long. That might not sound so bad, but the human body needs to be pushed to its limits to avoid plateauing. People need to keep interested in their workouts in order to stay motivated. The key to a successful cardio routine is variety. Anyone can easily shake things up by adding fresh elements to everyday ...