It helps regulate hormone levels and provides energy. And ladies, stop using dumbbells for just light weight "toning" exercise! These marks are often the result of rapid stretching of the skin associated with rapid growth.There are plenty of excellent resources available and they can offer some invaluable advice on nutrition and exercise. Increased levels of lactic acid have nothing to do with muscle growth and may actually slow down your gains rather than speed them up. We used to believe that it muscle building was the aging process that caused this but now we know different. First, we'll look at the importance of food and proper diet.