Just throwing this out there because it seems to be a mystery to most. In my last 6 IM attempts I have had to DNF in 3 due to extreme nausea. Symptoms are that I come off the bike feeling pretty good and sustain a comfortable pace for 10 or so miles and at this point I start to feel tightness at the back of my neck and slight headache. It starts to unravel from there and the nausea starts to come and I will either dry heave or vomit anything I take in. The 3 races I managed to finish I ran/walked/puked for 13 miles. The nausea continues for hours in the med tent and over night after the race. Anti nausea meds don’t even help. I would compare it to sea sickness or motion sickness which I have only experienced once on a deep sea fishing trip. I am a woman 60+ and this problem started occurring at age 57. I hadn’t raced in 3 years and so this was a new development. I raced for years prior to this successfully without this being a problem. I have consulted with nutritionists, coaches and have been scoped for Ulcers and other upper GI problems. Sodium levels in the med tents are always normal and I am well hydrated. This never happens in 70.3 races or on my long training days which consist of 6 hour ride followed by a 60’ run. I am fit and typically in the top of my A.G. I am not sure whether to pursue the IM distance anymore. Looking for educated thoughts.