Common fitness myths include the belief that lifting weights makes women bulky, which is unfounded; women generally lack the testosterone levels necessary for significant muscle growth. Another myth is that cardio is the only way to lose weight, while resistance training significantly contributes to fat loss and builds muscle. Some believe that stretching before exercise prevents injury, but it might actually lead to decreased performance if done excessively. Understanding these misconceptions is crucial for fostering a safe and effective approach to fitness.