Whether in training for a specific sport or event or working out to reach a particular goal, we all want that heart-bursting-through-the-chest feeling — it means we're really pushing ourselves to the limit. Sometimes we get that feeling by sprinting or running long distances, by lifting our max at the gym, working our butts off in a group fitness class like boot camp, or by out-hustling others on the court or on the field.

Few workouts are as challenging as High Intensity Interval Training, and fewer yet yield the benefits that HIIT does. Much more effective than a steady cardio session, the short-but-intense activity of a HIIT workout boosts aerobic and anaerobic endurance, ignites your metabolism, and gives you a monstrous calorie burn, all while maintaining or even increasing muscle mass.