I swim once a week for cardio. It is fabulous cardio exercise. I've injured my knee, so I can't run at the moment, but when I was running, I would see a marked improvement in my running endurance (e.g., I could set the treadmill a little faster) every week that I swam. It was remarkable.
Swimming is also great for injuries. When I first injured my knee, I refused to accept it and continued to exercise and ended up injuring my ankle as well. I think it was a mild strain--no bruising or swelling, just really painful to walk on it. Swimming seemed to make it feel better and my ankle would be more flexible when I finished the swim.
When I first start swimming, I just got in the pool and tried to do laps. I did eight laps of freestyle, then eight laps of breast stroke, then another eight laps of freestyle. I also threw in a few sets of eight laps of flutter kick or frog kick (the kick you do with breast stroke) to give my legs more of a workout and for a change of pace. I did that for an hour, but you could do if for however long is comfortable for you. The first swim was killer, but the second one was easier, and the third even easier. As I said, swimming is a fantastic cardio workout. If you do it regularly, you'll be surprised how quickly you progress.
As I got better at it, over the next year or so, I concentrated on improving my workout in the following ways:
- Eliminating any rests in the middle of sets and reducing my rest period between sets. Eventually doing flip turns on the freestyle sets.
- Adding a couple sets of eight laps of back stroke.
- Replacing some of the breast stroke sets with freestyle intervals. For eight laps, I alternate between swimming as fast as I can and then swimming a lap at a recovery pace. When I first started the intervals, I did breast stroke for all the recovery laps. The I focused on trying to do freestyle for the recovery laps. The next step was to add flip turns. I currently include four sets of 8-lap intervals in my workout: three with freestyle recovery and flip turns, one with breast stroke recovery (and only four flip turns because flip turns and breast stroke don't really mix). I could probably do all four sets with freestyle recovery, but I'm a breast stroker at heart (that was my stroke when I swam competitively) and it's my reward for doing the other three sets with freestyle recovery.
- Trying to swim a lap underwater without coming up for air. This is the way I finish my workout and I added it maybe six months ago. The first workout I tried it, I only made it halfway across the pool. By the third or fourth workout, I could finish the whole lap without a breath. Did I mention swimming is a fabulous cardio workout?
My most recent improvement is to buy a pair of swim fins and use them for the sets of flutter kicks. Awesome! But you don't want to do this until your ankle is completely healed, because it is very stressful on the ankle (it would definitely fall in the "overdoing" category).