Swimming is an all-body exercise. A physically demanding combination of cardio and power, it works your heart, and the muscles in your legs, arms, torso and hips. The constant resistance from the water forces your muscles to simultaneously contract and stretch, creating flexible and resilient muscle fibers.To increase the efficiency of your swimming, it's helpful to know which muscles you are using in each stroke and how to strengthen them.
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Freestyle and Backstroke
In freestyle and backstroke, your arms pull and push underwater, but you also must maintain your torso's position in the water itself so you're exercising not only your triceps, biceps and deltoids but also your abdominals, gluteals, ribcage intercostals, chest pectorals and hip stabilizers. In freestyle and backstroke, you use a flutter kick, engaging predominantly your quadriceps in the freestyle, hamstrings in the backstroke, and to a lesser degree, your calf and foot muscles.
Breaststroke and Butterfly
Breaststroke and butterfly require lifting your head out of the water to breath, an action that depends largely on arm and leg power, not neck-strength. Breaststroke's arm movements are sweeping actions underneath you, front to back, that engage the pectorals, biceps and deltoids. Your triceps help you thrust your arms forward, ahead of your head, when you take your breath above the water's surface. The simultaneous frog-kick backwards works your gluteals, quads and hamstrings. The calves activate when you flex your ankles straight to finish the kick. The kick is similar to leaping off the floor from a squat. Butterfly is the most energy-consuming stroke and involves the torso and hips as much as the arms and legs. Your chest lifts upward through the water's surface with every stroke, forcing your shoulders and arms to pull hard underwater toward your hips. Your abdominal and back muscles undulate your body through the surface. Your lumbar, hip and gluteal muscles continue the undulation down the legs and produce the sharp kick downward.
Water Resistance and Weightlifting
The World of Sports Science website describes how swimming requires your muscles to overcome frontal resistance, skin friction and eddy resistance. You have to power through water turbulence and the drag you create, so weightlifting is important in supplementing the cardio. You should work the major arm and leg muscles, plus the hip, gluteal, lumbar and abdominal muscles because they all assist in rotating and stabilizing your body in the water. Water is a highly unstable environment, so weight-training two to three times a week to strengthen your core will improve your overall form. The website Weightlifting Guidelines for Swimmer provides routines to improve your muscle function.