The quad cab has a smaller back seat and a larger bed, the crew cab has a larger back seat and a smaller bed. To compare them you can go to http://www.ramtrucks.com/en/2011/ram_150... and select the Build My Own option from the bottom of the page.
Heart muscle thickening (called cardiac hypertrophy) can be a healthy response to exercise and pregnancy; however, it often occurs in people with high blood pressure, diabetes, heart failure and certain genetic conditions.
Too thick or too stiff. The heart's ventricles can have trouble filling with blood for two main reasons. Overworked heart muscle can bulk up, like a weightlifter; this reduces the open space inside the ventricles. Alternatively, the heart muscle may stiffen and become less flexible.