I play handball (think racquetball, but without racquet's) for fun and cardio. 2 games to 21 and a possible tiebreaker to 11 make up one match. I've got no problem playing a full match, but in tournament formats, I sometimes have to play back to back matches. The thing that cost me in the state tournament last month was having no legs or lungs in the second half of a double-header. My question to you all is other than playing more handball, what can I do to build up my endurance? Long sessions of cardio, HIIT? Right now I'm running 4-5 days a week usually 1-5 miles at a time.