What are you made of?

I have taken pride in the fact that I have never in my life found myself hunched over losing my lunch due to the fact that my body could no longer hold it in as a result of excess physical exertion. With 5 seasons of cross country and 4.8 seasons of track, I have never throw up from a work out or a race. Lately, though, I have started to wonder what that meant about me. When one pictures themselves finishing a 5K or 8k race, the thought is of tearing through the line as fast as you can, and then stumbling toward the nearest course volunteer so they can hold you up as they walk you through the finishing chute. You get to the end, take your number, and are passed of to the nearest teammate of the opposite gender/of the differing level of competition (Varsity or JV) who then helps you hobble back to your site.
I have no experience of this. I have blown through the line having raced a 27:32 8K, run the last hundred meters in 12.3 seconds, and still just put my hands atop my head to help me breath, but walked through on my own, and stood at the end of the finishing flags welcoming and congratulating every contestant as they came through. I have run 24 400 meter repeats at 70 seconds with 70 seconds of rest between, and then run the 25th at 63 seconds. I have PR'd in the 800 meter run by two and a half seconds and collapsed  afterwards for over an hour. But I have never tossed my cookies.
I wanted to change that today. I asked my mom to come to a local park with me where I had a 850 meter loop, and I told her to not let me stop running until I yak'd. This loop has a big uphill, a treacherous downhill, and I would have to dodge frisbee disc golfers as I ran. I warmed up with a lap, then got straight into the workout. I ran the first lap in 2:44 seconds. by the third lap, I felt like tossing. By the fourth, my legs were hitting together. By the sixth, I could barely make it up the hill, and my mom said one more. She made me go for three. I finished my ninth lap in under 27 minutes, and my legs folded under me. I couldn't run any more. I couldn't breath. Even after a minute, I couldn't say a sentence without abrupt stoppages in speech. I could feel my stomach wanting to revolt. It was at my sternum. It had been as high as low in my throat, and filled my entire abdomen. But it would not come up. I still had not puked.
It ends up my stomach is stronger than my legs. I could hardly stand, and after 3 minutes, I could only stumble instead of walking a straight line. I couldn't run farther, but I still held my lunch inside.
It ended up making me feel better that I hadn't run to expulsion before. As it turns out, I can't. Good to know.