Anytime I move, my heart starts raising its rate to keep up with my workload. Virtually, all of my training has a cardiovascular component to it. A couple of times a week, I do some pure cardio work to train my heart and lungs.
When I am on the ice, I can consider it a strength and cardio workout. Even skating slow laps requires a great deal of strength, and my heart rate increases to a high level before long. I do two types of specific cardio work, mostly on a stationary bike sometimes on the ice or slideboard.
One type of workout is interval training. The other is extensive tempo. The difference is that interval training is of a higher intensity but with rest between the efforts. The extensive tempo training is doing something at a lower intensity but continuously for a longer time frame.
An example of an interval workout would be running 400 meters pretty hard so that you are breathing heavily at the end, then resting by jogging 200 meters, then repeating. This was the workout we did when I was in high school as a freshman running cross-country, and we repeated this cycle about 12 times or more in a workout. It takes about an hour to do this part of the workout.
An extensive tempo workout would be running for the same hour or longer but at a slower pace continuously. Both types of workouts have benefits for your heart and lungs. If you are not in very good condition you must remember to increase your volume and intensity very slowly! Otherwise, you will get injured and have to stop or scale back your training. Even if you are in great shape, increase slowly!
To get the full benefits of cardio training, you should use both methods each week. Many times, my coach schedules an extensive tempo bike workout in the evening after an intense morning workout on the ice to help flush out the byproducts that built up earlier. This way I get the benefit of the flush as well as the cardio training for my heart. Swimming is also a great non-weight-bearing exercise that can help with heart and lung capacity. I can do tempo, intervals, or recovery work by swimming.
Here is a video of the end of an interval workout on my stationary bike that I sent to my coach Nancy Swider-Peltz, Sr who was in Germany at the time.