Will crunches make you lean or will it make your tummy bulk up?

Answer 1

Crunches were developed to keep the stomach lean. They work a shorter range of the muscle making it more ripped, not bulky.

Crunches will build (grow) the abdominal muscles over time. How much growth is dependent on diet, intensity and consistency. That alone is usually not enough to effect an overall body slimming. This is due to the fact that fat is burned when glycogen stores are depleted and the body resorts to tapping into fat reserves to continue its course. Oxygen is the enabler in this relationship. The more efficiently oxygen can be used in this process the quicker and more dynamic the growth will be.

Abdominal muscles are smaller, leaner muscles in general and therefore don't require a lot of oxygen and glycogen before they reach optimal fatigue point (think about how quickly they start to burn after a few well executed crunches).

Leg, chest or back muscles are large and require more effort to fatigue. That means glycogen is depleted and fat is called upon to continue the exercise. This balanced approach to exercise is how people are able to lower over-all body fat levels. Once a person has achieved this level of fitness the abdominal muscles are thus visible.

Ironically, popular sentiment touts rock hard, well defined abs as the reason to fitness when they are merely a result.

So, to answer the question: no, abdominal exercises alone will not make one lean. And no, they won't bulk up the tummy area to speak of. The reason is because if all you are doing is abdominal exercises your not going to have any real muscle growth there other than good toning.