I walked/jogged (mostly walking) an hour and swam an hour today. When I swim an hour, I swim an hour - no stopping. Not fast but continuous. Paddling and walking had my muscles in good enough shape to do it. Not the first time I swam; then I got about half an hour before needing a break. But the last couple of times I have. I get out of the pool pretty drained - it's a good workout.