Word of warning with this YouTube workout: it's probably the hardest cardio workout I've ever done. If I remember correctly, it almost reduced me to tears the first time I tried it, but it was tough to tell the tears from the copious amounts of sweat pouring off me. That being said, there's a reason I keep coming back to it, and it's not because I love the literal sprints at the midway point. The instructors are amazing, the music is on point, and the moves are seriously effective.