Working your lungs and heart in the water will make them stronger.
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Swimming is an excellent form of exercise that works a wide range of muscles. When you are swimming, the working muscles of your arms, legs and core are demanding additional oxygen, and this makes your heart pump faster. As a result of regular swimming exercise, your heart will become stronger and able to pump more blood with each contraction. Your lungs, meanwhile, adapt by learning to absorb more oxygen -- and the muscles in your diaphragm and ribs that control your breathing become stronger, too.
The long-term effect of regular swimming is that you will have a lower resting pulse and breathing rates. A slower pulse is a sign that your heart is stronger and capable of pumping more blood with each contraction. It's also an indication that your blood vessels may be more open and flexible than they were before you started swimming regularly. The lower breathing rate reflects the increased lung capacity and efficiency that comes from exercise.
How Much Swimming
The American Heart Association recommends that you exercise at a moderate level at least 150 minutes a week, or at a vigorous level for roughly 75 minutes a week. Swimming is an excellent way to achieve these benchmarks because it is considered low impact. The water has a cushioning effect, so the body doesn't have to endure the jarring impact from running, for example. Swimming is a good alternative exercise for people with injuries or health conditions that restrict their activities on land.
Lung Problems and Swimming
According to the University of Maryland Medical Center, swimming is particularly beneficial for those with asthma, a condition that can be exacerbated by running in cold, dusty or polluted air. The humid air of a swimming pool may also help those who suffer from exercise-induced asthma triggered by cold, dry air. In general, people with lung problems can improve their breathing by beginning a swimming exercise program and slowly building up the amount of time they exercise.
Swimming and Heart Rate
If you are using your heart rate as a measure of how hard you are swimming, you should be aware that your heart rate will be 10 to 15 beats per minute slower in water than it will be when exercising on land at the same intensity. The water helps keep the body cool, and its hydrostatic effect improves blood flow. Also, you're usually in a horizontal position. All of these factors will keep your heart rate from climbing as high as it would while exercising on dry land.