The main set of my swim workout today included 10x25s building from start to finish. I really enjoyed them, because right about the time I started to feel like toast, I got 5 seconds of rest at the wall.
After I finished the main workout, I had a little bit of time left so I swam an extra 350 yards. Since it was just "extra" I decided to take it easy and just glide.
Lately, I've been thinking about the purpose of tempo/speed work in all of my workouts. At first my thought was it helps me to build endurance in that zone, which, it does, and push my overall speed to new levels, which it does. But today while I was gliding through the water, I discovered another purpose of the speed work--to make the aerobic zone feel easier. I was not swimming slow during those 350 yards (well, I guess it's all relative, but it wasn't slow for me), but it felt easy. I thought at one point, I could just swim all day long like that...which is the point, right?