Swimming doesn't just work out one part of the body; it conditions the entire body, including your legs and core. No matter what stroke you swim, strengthening your legs and core can only improve your overall speed and efficiency. You can make progress on the butterfly, breaststroke, backstroke and freestyle strokes by practicing kick drills and building core strength muscles through swimming drills.
Using a Kick Board
A surefire way to focus on your legs during any swim workout is to use a kick board. Hold it in front of you with your hands out, but not gripping the board too tightly, as this will freeze up your hips, which need to stay relaxed. To really develop a good dolphin kick, flutter kick or breaststroke kick while you strengthen your legs, keep up the interaction between hip and leg muscles as you kick with the board. You can do this by kicking near the surface of the water without splashing, using your entire leg. This includes your feet, calves, thighs and hip flexors. Moreover, kicking vertically with the kick board above your head works out your core. Try holding it over your head while you practice the dolphin kick -- you'll instantly feel your abdominal muscles being worked in the water.
If you have a weaker kick -- and weaker legs -- you can gain muscle by adding fins to your workout. Fins increase ankle flexibility, as you stretch the foot more each time you kick down. The blade on the fin puts greater pressure on your leg muscles, much like working out with a weight around your ankles. Your kick improves and you use your legs more, giving you a higher-quality workout. Again, kicking vertically will help work out your core, and doing so with fins on with bolster your leg workout.
The egg-beater kick is used more in drills for water polo, but it's equally useful in swimming. Because it propels the body and uses the natural resistance of the water to build leg strength, practicing the egg-beater kick helps keep your calves, shins and glutes strong. To do it, float upward in the water with your thighs straight and your knees bent at a 90-degree angle. Rotate your calves in clockwise and counterclockwise motions, controlling the movement with your hips. The more you bend your knees, the more you'll feel the burn in your leg muscles. Balance the rest of your body by stretching your arms out on either side. Best of all, egg-beater kicks already work out your core because you are forced into a vertical position. Think of it as "water running," which can increase core strength.
Oftentimes, the reason a kick is slowing you down is because your hips and legs are dragging due to poor balance. To fix this, you need to redistribute your weight by leaning on your chest while swimming and raising your hips up. A balanced body will keep you afloat and ease up how hard you have to work to maintain forward momentum. Start by focusing on your body's position during the warm-up, looking to correct your hips and legs. For the core, keep your back aligned with the rest of your body. Focus on streamlined swimming, with your core acting as a stabilizing force in the water.
Nadia Osman is a California-based writer. She has covered travel, real estate, fashion, fitness and other topics for various online publications. Osman holds a B.A. in history from UC Irvine.