Fitness Model vs Female Bodybuilder Abs Contest

A fitness model and a female bodybuilder is having a contest to see who has the strongest abs. After 5 hours of sit-ups, none of them won't give up. The female bodybuilder challenged the fitness model to do sit-ups with a knife in the navel. Both girls took out their knives and stabbed it halfway into their own navel. They then continued their sit-up. After 5 more hours, both girls were still going strong, so the fitness model suggested to stab the knife all the way to the hilt. With the full knife now inside the navel, they then continued their sit-ups.

Who do you think would die first? The lean fitness model or the muscular bodybuilder?