In the past seven years I have raced nine long course events, six half-ironman distance, and three ironman distance. I have dnf’d six of these events due to extreme stomach upset. Even in the three events I was able to complete I still got sick to some degree. The progression of events has been essentially the same in every case. I do fine on the swim and through a substantial portion of bike. In some cases I have been able to stave off illness until the early- to mid-stage of the run. Regardless of when it occurs, at some point I begin to become extremely fatigued and my stomach begins to feel very heavy. Continuing beyond this point usually results in vomiting. Once the vomiting starts it sometimes continues for many hours. Even IVs and anti-nausea medications are not always immediately effective to stop it. I have struggled to find a solution to this problem. At various times I have believed the issue was either inadequate conditioning or nutrition. I have tried many different training systems (most recently using VC on tb.com) and many different nutrition strategies. I have also experimented with pacing. I typically have no problem in training unless the sessions extend beyond 3.5-4.0 hours. After my most recent failures at California Half and Wildflower I have started to believe that I may have some physiological condition which is a barrier to endurance performance. I have also been wondering if it could have something to do with my breathing pattern. I have noticed that my breathing tends to be fairly shallow and through my mouth. I would appreciate any and all comments. I am happy to provide more background here or offline to anyone who thinks they have something to contribute. I am male, age 39.