There are natty bodybuilders and powerlifters. There are even natty vegan lifters. For bodybuilding half of it is just being low bodyfat.
Earlier someone mentioned creatine as a supplement. Higher creatine levels provides your skeletal muscles with more raw energy when muscled are taxed for strength (as opposed to endurance), leading to your tissue adapting to the higher load by building up. It also increases the amount of H2O in your muscle cells which has some positive effects. As a downside some people can look puffy-fat on it. Its legal, safe, and pretty cheap. The effects are much smaller than AAS, which of course are unsafe and illegal in many places.
|