Does Running Build Leg Muscle?

If you're starting or increasing a running program, you probably know that running is great for your cardiovascular fitness and overall health. But you might wonder if running gives you muscular, or runner's legs. The answer is a qualified yes - because running primarily uses your legs, you will develop sport-specific muscles over time. No matter what type of exercise you do, some degree of resistance is being placed on your muscles when you work out. When a higher level of resistance than usual is placed on your body - like during a workout as opposed to doing regular daily tasks - this triggers your muscles to grow. To counteract this process, your body makes new muscle proteins to repair this damage. This is called muscle protein synthesis, according to the International Sports Sciences Association (ISSA). Depending on whether you are jogging or sprinting, you utilize one of two types of muscle fiber: slow-twitch or fast-twitch.