Swimming is the second most popular sports activity, reports the Centers for Disease Control and Prevention. This aerobic activity uses most of your major muscle groups, so participating in regular aerobic exercise like swimming provides health benefits. You must swim at a safe pace for your fitness level to avoid lactic acid buildup that can cause swimming cramps or sudden involuntary muscle contractions.
Your muscle cells need energy in order to contract. In normal day-to-day activities a chemical reaction within the muscle cells uses glucose -- the form of sugar in the blood -- and oxygen to produce ATP, adenosine triphosphate that it then burns as energy. During intense exercise, this reaction occurs too slowly to provide the muscle with enough energy so it uses glycogen, a storage unit for glucose in the cell. When the muscle cells break down the glycogen, a process that does not require oxygen, it produces the by-product known as lactic acid.
All aerobic activities require oxygen. While swimming, keep your stroke steady and rhythmic so that you can keep breathing to supply oxygen to your muscle cells. When the swimming becomes strenuous, your breathing becomes labored and you cannot provide sufficient amounts of oxygen to your cells. To keep working, your muscles then stop performing aerobically and begin the anaerobic breakdown of glycogen leading to the production of lactic acid.
As lactic acid builds up in the muscle, it increases the acidity of the cell and surrounding fluids. The chemical reactions necessary to break down glycogen and use it as energy do not like acidic environments, so the production of energy slows down, affecting the muscles' ability to keep contracting. This causes your muscles to become fatigued. Continuing to swim and trying to use muscles that do not have enough energy to keep contracting can contribute to muscle cramps while swimming.
Muscle cramps can occur during any type of exercise such as running, swimming or cycling. Dehydration, strain and fatigue can contribute to the onset of a swimming cramps. Although there is no way to prevent swimming cramps in all cases, make sure you drink plenty of fluids before, during and after your swim and go at a comfortable pace that allows you to breathe regularly and deeply. Take in enough oxygen to support the aerobic production of energy and decrease your risk for lactic acid buildup.