Swimming can tone muscles, but not as well as weight training.
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You've probably heard the expression "swimmer's build" to describe people with a lean, toned physique -- and for good reason. Swimming helps you manage your weight while providing some muscle-toning benefits for a sculpted appearance. That said, swimming cannot help you develop muscles as effectively as weight training, so include both in your routine for the best definition.
Swimming for Muscles
Swimming is a multitasking activity, according to Janet Evans, author of "Total Swimming," who claims the exercise can lengthen muscles while building endurance and strength. Evans reports that because water creates more resistance than air, swimming can sculpt muscles for added shape and increased function. Many strokes rely heavily on core muscles in the back, stomach and hip areas, and Evans states that these areas will enjoy the most sculpting. For effective toning, aim for intense swimming sessions of 30 minutes or shorter -- long bouts of aerobic exercise may actually reduce muscle mass, according to Columbia Health.
Swimming vs. Weight Training
Despite having some muscle-building benefits, swimming is primarily an aerobic endurance activity, making it more effective for cardiovascular conditioning than muscle building. Weight training exercises, in contrast, use a higher resistance level and therefore place more stress on muscles. This stress, and the recovery that follows, is how muscles grow. Therefore, to achieve a "cut" appearance, you'll likely need to lift weights, perform body-weight exercises such as squats and pushups, use resistance bands or engage in other weight-training activities.
Swimming and Fat Loss
Swimming may not be your go-to activity for building muscle, but aerobic activity is still important for managing weight -- and if a layer of fat covers your muscles, nobody will be able to see them, anyway. Swimming laps using the butterfly stroke, a 155-pound person burns about 409 calories in 30 minutes; lifting weights, she burns just 112 calories in the same time. One pound of fat equals about 3,500 calories, so it's possible to lose 1 pound in fewer than nine swimming sessions while it could take more than 30 sessions with weight training alone.
For optimal fitness, swim or perform other aerobic activities for 150 to 300 minutes each week. If you work at a vigorous intensity level -- meaning you get winded after speaking a few words during exercise -- 75 to 150 minutes per week will do. In addition, perform weight training for all body regions at least two times per week, allowing 48 hours of rest for muscles to repair and develop. If you're currently sedentary, visit your physician before starting an exercise program.