Accomplished swimmers seem to glide effortlessly through the water, using coordinated arm and leg movements to move from one end of a pool to the other. For others, the effort to swim is a constant struggle to breathe correctly and stroke efficiently.

To perfect technique and improve aerobic conditioning, swimming experts recommend that people learn how to do the strokes correctly. Enhanced skills help swimmers avoid wasted motions. There are five basic strokes:

Freestyle or crawl. Most people who swim for fitness use the front crawl, said David Stevenson, associate director for programs at the National Capital YMCA. Mechanically, it may not be the easiest stroke to learn because there are several techniques involved. Swimmers must master rotary breathing -- turning the head to the side to breathe -- and the flutter kick, a constant movement of the legs that must be synchronized with each arm stroke.

Breaststroke. The breaststroke is a popular choice because swimmers don't have to do rotary breathing. The arms move in a symmetrical motion with the legs, unlike the front crawl where the legs are constantly kicking. This stroke works the muscles in the inner and outer thighs and the arms.

Backstroke. For new swimmers, this can be an uncomfortable stroke because they are on their backs. "Unless you develop a technique," said Stevenson, "it is hard to watch where you are going." Experienced swimmers learn to tip their heads down toward the bottom of the pool and glance backward. Others count the number of strokes needed to cross the pool.

Butterfly. The most difficult stroke to master because it requires excellent coordination and precise timing. Arms must move in time with the legs. The kick, called a dolphin kick, requires both legs to be together with the thrust originating from the hip. "A lot of people can't synchronize the kick with the arms," said Patty Bacha, water safety instructor and summer intern at Westin Fitness Center.

Sidestroke. A more relaxing stroke that is not as efficient in improving physical fitness. However, this stroke is a good choice for cooling down after a vigorous workout. This stroke burns about 8.5 calories per minute while the other strokes burn about 11 to 12 calories per minute, according to the National Institute for Fitness in Sports.

Aquatic experts advise swimmers to mix and match strokes to vary workouts. "The goal is for a person to develop their stroke to a point where they can swim comfortably," said Stevenson. "People who swim and stick with it usually get pointers along the way or develop their own strokes."