“If you swim the same pace every day,” Ms. Lepinski said, “you won’t get as much benefit.” For one, she added, interval training is more fun. “And two, it just challenges your heart a little bit better.”
Mr. Ksebati and Ms. Lepinski said a good beginner or intermediate workout is 1,000 to 1,500 yards, or 20 to 30 laps, which should take about half an hour. Begin with a short warm-up — maybe a 4×50 at an easy pace — to get your heart rate up. You can mix in different strokes, doing breast or backstroke instead of freestyle for a little variety. Next do a 4×25 using a kickboard to get your legs activated.
Then comes the main set, or the bulk of your workout. If you’re working on speed, do 8×50 (eight laps with a break after each) at a fast pace. If you want to increase endurance, try a moderately paced ladder, ascending and then descending the length of your intervals: 1×50, 1×100, 1×200, 1×100, 1×50.
Last comes the cool-down, another 4×50 of swimming at a relaxed pace. You can take a longer break — one or two minutes — in between the warm-up, main set and cool down.
It’s a little confusing at first, but once you get the lingo you can follow almost any swim workout. Want even more structure or a goal to work toward? Apps like MySwimPro provide customized workout plans, or you can find your local U.S. Masters Swimming team. (In the swimming world, “masters” just means adult.)
Most of all, enjoy the process. For many swimmers, the water isn’t only a place to work out, it’s also a sanctuary. “It’s hard to be thinking about the stresses of the world when you’re thinking about, ‘When’s my next breath? Where’s the end of the pool? What set am I on?’” Ms. Lepinski said. “When we slip under the water, the world goes away.”