jojoclown777 wrote:If by "handy" you mean scientifically-based, then yes, handy. There's mad research pushing both 10 and 75% (or is it 80%?).
The aerobic threshold (as in the point at which exercise should translate into gains to the aerobic system) is 'supposed' to be somewhere about 70% of your maximum H.R. Which, yes, can be somewhat ambiguous. Agreed with the stair running though, provides a nice little platform for some interval training at a high heart rate.
Pools do give someone an opportunity to mix it up a whole lot, from aquaerobics to slow laps, fast laps, using a kickboard, treading water with your hands above your head, treading water with your hands above your head holding a medicine ball and sets of kicks while holding the side of the pool are some of the ways cardio can be achieved in the pool.