Anaerobic Vs. Aerobic Swimming Workouts

Man swimming butterfly stroke in race

Whether you swim the 50-meter freestyle in the pool or compete in 5k open water swims, optimal performance depends on a balance of aerobic and anaerobic swim workouts to hone your cardiovascular endurance and sprint speed, respectively. Anaerobic energy production doesn't require oxygen and helps you sprint a 50-meter freestyle race. However, your body cannot sustain anaerobic energy production for more than two to three minutes. Therefore, in long-distance races such as the 800-meter freestyle and beyond, you rely primarily on aerobic, or oxygen-utilizing, metabolism to provide your muscles with sustained energy.


Whether your body uses aerobic or anaerobic mechanisms to break down cellular energy, or ATP, depends on your swim intensity. Aerobic energy production uses oxygen to convert carbohydrates, fats and a minimal amount of protein into ATP, which the muscles use for energy. Although your body can use aerobic processes to generate energy for hours, these processes are relatively slow and will not supply the quick energy necessary for a 50-meter freestyle or 100-meter butterfly. Anaerobic processes produce ATP rapidly; however, your body cannot sustain this rate of energy production for more than a couple of minutes because ATP yield is much smaller than from aerobic processes.

Aerobic Workouts

The primary goal of aerobic swim sets is to improve your cardiovascular fitness and muscle oxidative capacity by sustaining a moderately high intensity — 65 to 75 percent of maximum heart rate — for 15 to 30 minutes at a time, with minimal recovery between intervals. Aerobic swim sets are particularly important during the first eight to 12 weeks of training to prepare you for high-intensity workouts and competitions later in the season. An example of an aerobic swim workout would include four sets of four 100-meter swims, with the first set on an interval giving you 20 seconds rest and decreasing the interval by five seconds per set.

Anaerobic Workouts

Anaerobic swim workouts involve short-distance intervals — usually 25 to 125 meters per interval — at 90 to 95 percent of your maximum heart rate with long rest periods. These workouts train your muscles’ ability to buffer lactate, a primary byproduct of anaerobic energy production. Subtypes of anaerobic training include 50- to 100-meter sprints with up to five minutes rest, which allows some lactate clearance from the muscles between intervals, or swimming the sprints with one to three minutes rest, which results in more lactate buildup by the end of the workout. Since anaerobic workouts are physically and mentally difficult, you should only do these workouts once or twice per week to ensure you are sufficiently recovered.

Workout Design

Interval training, a staple component of swim workouts, involves manipulation of the number of repeats in the set, the distance of each repeat, the rest interval between each repeat and the speed of each repeat. You can adjust one or more of these four variables to make a workout more or less anaerobic. Increasing the number of repeats or the distance of each repeat or both typically increases the aerobic training effect of the swim set. Conversely, increasing the length of the rest interval and your swim speed will make the workout more anaerobic. However, there are exceptions to these general rules. For example, decreasing the rest interval in a long-distance set could make the workout more anaerobic if you have to increase your speed to swim under the interval time.