The powerful and graceful strokes of champion swimmers belie how difficult it is to function efficiently in water. Working with a swim instructor is beneficial. Coaches can tailor workouts to improve a swimmer's technique and fitness, and participating in group practices benefits swimmers of all ages.
Definition
Physiology is the study of the systems that allow a living organism to function. The physiology of exercise in swimming focuses on how a human body propels itself through water. Scientists and coaches study how training affects performance and how technique helps overcome the force of water against a body in motion.
Water/Mechanics
According to USA swimming, the National Governing Board of swimming in the United States, water impedes the forward motion of swimmers in three distinct ways. First, humans must overcome the resistance of water. Minimizing resistance involves improving position in the water and stroke technique. Second, swimmers must deal with the water turbulence they create when moving through it. In swimming pools, staying underwater when making turns helps the swimmer avoid the wake created a few strokes before. Third, friction caused by contact between fabrics or skin and water slows a swimmer. Special suits that cling to the body and compress it minimize friction. Swimmers often shave their body hair before a race, hoping to shave off a few fractions of a second from their times.
Muscle Function
Swimmers use muscles to propel themselves through water. Muscles have cells that contract. Those cells link together forming muscle fibers, and when those fibers contract in unison, motion occurs. The cells rely on ATP or adenosine triphosphate molecules to contract. When ATP breaks down, releasing one phosphate molecule, the process releases energy. Muscles use the resulting energy to contract.
Once the ATP breaks down, the body needs a fuel source to rebuild or recycle the elements back together to maintain movement. Substances such as creatine phosphate and glycogen rebuild or relink the phosphate back with the adenosine--reloading the energy source. Limited amounts of creatine phosphate stored in muscles quickly function to recycle ATP. Glucose, or carbohydrates, commonly stored as glycogen in muscle tissue and the liver, do the most work in recycling ATP.
Fat reserves in the body serve as an energy source only in prolonged endurance workouts. The breakdown of fats into substances that rebuild ATP takes longer and is less efficient than the action of carbohydrates.
Energy Metabolism
The body generates energy in two ways: By aerobic and anaerobic metabolism. Anaerobic metabolism takes place without oxygen, and it occurs in the first steps of the breakdown of glycogen. One byproduct of the energy genesis is lactic acid. When lactic acid builds up in muscle tissue, athletes experience fatigue and pain.
Aerobic metabolism relies on oxygen, and completes the breakdown of glycogen in a process called the Krebs cycle. Aerobic-derived energy takes longer to synthesize; slow to moderate swimming relies heavily on aerobic capacity. Sprinters use anaerobic capacity for short intense bursts of speed.
Coaches vary workouts to include aerobic and anaerobic training sets. Aerobic training focuses of improving the swimmer's cardiovascular function and lung capacity and the efficiency with which they use available oxygen.
Speed Versus Endurance
Muscles contain two types of fibers. Fast-twitch fibers contract up to 50 times per second, whereas slow-twitch muscle fibers contract at around 10 to 15 times per second. Sprinters use fast-twitch muscles for bursts of speed that rely heavily on anaerobic energy. Slow-twitch muscles benefit from aerobic energy, making them ideal for distance or endurance swimming.
Heredity influences what type of muscle fibers a swimmer has, making some swimmers natural sprinters and others endurance athletes. Training cannot change the makeup of the muscle fibers.
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