Feeling tired after an intense workout makes sense, but lingering fatigue might leave you wondering about its cause. Swimming is a low-impact exercise that allows you to get a good cardiovascular workout without stressing your joints. The weightless environment insulates and protects you from the effects of gravity and also keeps you cooler when you exercise in hot weather. Despite swimming's benefits, though, certain factors influencing your swim routine can lead to chronic fatigue.
Swimming is an energy-intense form of aerobic exercise that uses all the major muscle groups in your body. You build up strength and cardiovascular fitness gradually; when beginning a swimming routine, take it easy for the first few weeks. Swimming requires excellent lung capacity and efficiency, and takes a different skill set than land-based exercise. Don't make the mistake of forgoing nutrition in the hours leading up to your swim. During sprints and intense workouts, you rely on carbohydrates for fuel, and if you get in the pool hungry your performance and energy levels will sink. And even though you won't notice the fact that you're sweating, you will; so drink plenty of water.
Efficiency vs. Force
The harder you swim, the less efficient your stroke becomes. If you fight against the resistance of water rather than slipping through it, you expend more energy every lap you complete. Rotate your body when you swim freestyle and backstroke, but keep your head still. Don't lift your head when you take a breath; instead rotate if along with your body, exhaling underwater, and then taking a breath when your cheek emerges above the water. Even if you are a distance runner, you can get exhausted quickly swimming unless you learn proper breathing techniques and time your breaths to your swimming stroke.
You might feel fatigued after swimming if you have an existing condition or if you are recovering from and illness or injury. Asthma makes breathing during exercise harder than normal, and the chemicals used in pool-water disinfection can cause asthma-like symptoms in otherwise asymptomatic athletes. You might suffer the lingering effects of bronchitis or upper respiratory infection, and even though you feel well enough to workout, you'll feel fatigued afterward, so take time to recover fully after an illness before heading out to the pool.
Taking on too heavy a workout load in the pool can result in burnout and fatigue. Adding more pool time and increasing the intensity of your workouts helps improve your fitness, to a point. Any repetitive motion puts strain and wear on the muscles you use during workouts, and any flaw in your technique gets magnified when you repeat the mistake hundreds of times a day. Check with a swim coach to troubleshoot your stroke, and take a few days off to let your body repair itself.