Swimming is one of many diverse types of aerobic exercises, all of which have their own advantages and disadvantages. Runners and cyclers, for instance, achieve different effects on their bodies than swimmers, and choosing between the types of exercise is usually a matter of what kind of activity you enjoy the most. If you need evidence to support your decision, there have been many studies comparing these sports in terms of calories burned, endurance gained, safety and other factors.
How many calories you burn during any exercise depends on a number of things including body weight, workout intensity and environment. If you swim laps at an easy pace with a freestyle stroke for one hour, you will likely burn between 413 and 651 kilocalories or 590 and 931 if you swim quickly. Compare that to running at nine minutes per mile, which will burn between 649 and 1024 kilocalories in the same time, or cycling at a moderate pace of 12 to 13.9 mph, which will burn between 472 and 745 kilocalories.
One of the gold standards of measuring athletic endurance is VO2Max, which refers to the maximum volume of oxygen an athlete can utilize during exercise. Studies have shown that swimming regularly does improve athletic VO2Max and it decreases maximal heart rate while swimming. But studies have also shown that this increase in swimming endurance does not raise endurance significantly in other exercises like running and cycling. All three sports are effective at improving endurance, and running seems to be the most successful exercise for cross-training performance, but no cross-training exercise ever exceeds the benefits of specific training.
Although swimming seems to burn fewer calories and have fewer benefits for endurance training than running and cycling, it does have a serious advantage when you consider safety. One study looked at triathletes, who perform all three exercises in tandem, and at the number of injuries that occurred in each part of a triathlon. They found that 50 percent of injuries came from running, 43 percent from cycling and only 7 percent from swimming. Swimming is famous for being a non-weight-bearing and low-impact way to get an aerobic workout, which means that the chance of injury remains relatively low even at competitive levels.
How swimming measures up against other forms of exercise depends on individual goals. For instance, because swimming is a better full-body exercise than running and cycling, swimmers have been shown to reach higher VO2Max levels during tests that involve upper-body strength. So if your aerobic goal is to improve your upper body and avoid injury, then swimming may be better. If your goal is to burn as many calories as you can and cross-train, running wins, and cycling may be a good middle ground. Doing all three, like a triathlete, can yield excellent results as well.