When I was 13-years-old my dad challenged me to do 40 situps every day for two weeks. I informed him after the two weeks that I successfully completed his challenge and planned to continue the exercise. And I did. I kept it up for quite some time. When I began to see the slightest definition in my 13-year-old abdomen muscles I was ecstatic. I naively thought that I could take it easy for a while