Competitive swimming is a demanding sport. It requires excellent aerobic conditioning for speed and endurance plus muscular strength in all parts of the body. Swimming uses every muscle group. Various strokes use muscles in slightly different ways, but each of the four competitive strokes uses all muscle groups. Male and female swimmers also use muscles differently, though both tend to have lean, well-defined muscles with trim waists and broad shoulders. Specific muscle groups used in swimming are the abdominals, biceps and triceps, gluteals, hamstrings and quadriceps.
The core muscles are most important in swimming. These are the large muscles of the trunk, which include shoulders, abdomen and hips. They control the basic positioning and movement of the body, including the arms and legs, which drive a swimmer through the water.
Shoulder muscles provide up to 90 percent of the propulsive force in most swimming strokes -- the front crawl, backstroke and butterfly. In those strokes, arms pull down through the water. The crawl and backstroke -- which is essentially an upside down crawl -- use a flutter kick while butterfly employs a double-leg dolphin kick. Legs provide more propulsion in the breaststroke, when the arms and hands are used in a sculling motion rather than a pull into the water.
Men vs. Women
Men generally swim faster than women because they have a higher percentage of muscle, although women have greater muscle economy because they have more body fat which makes them float better. They use less energy than men, but a man's greater proportion of muscular weight provides more power.
Because shoulders play such an important role in all swimming strokes, they are most subject to injury. Most shoulder ailments stem from improper stroke mechanics, which strain the muscles during the continuous movement required. The key shoulder muscles are the pectorals in the front of the chest, and latissimus dorsi on the back. They control the movement of the arm forward and backward.
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