Hardest core session I've done in a long time(probably since last year in August. .), plus an hour of pool running with intervals. 4:40 on, then break, then 1:30 on, 30sec. a bunch of different times, and a few 2 min. on, and 1 min. It hurt. I kept my head out of the water and was sweating, but the water was fairly warm, but it still is good to work hard enough that I sweat.