Intervals on different strokes. I would be pushing it on a 1:40 freestyle interval since I average from 1:27 to around 1:40 depending upon how I feel. 1:50 I could do and 2:00 I feel comforable with. I'm in my mid to late 40's, so 10 second rest intervals tend to make me stiff. I use 2:15 for breaststroke because I swim from 1:45 to 1:54 in workouts and I use 2:30 for fly because I swim from 1:46 to around 1:54 also in workout in 100 yard fly and fly is easier if you are not that tried. Backstroke an interval that gives me 20 seconds rest, that's my slowest stroke.
