Hyperventilation after T2

I second the advice that you should get checked out by a doctor to see if there is a medical reason for your symptoms, rather than something about your pacing, hydration, or nutrition.

If you check out okay, with the doctor, then I would start to look at a couple of things regarding your race execution:

1. Try easing off the pace a bit in the final stages of the bike (maybe the last 400m or so in an Olympic distance, 200m in a sprint) and not dashing through transition. Unless you're really in it to win it and your AG rivals (like mine a few years ago) are doing mean tactical things in the final km of the bike to try to block you into transition, then it's better just to stay calm and set yourself up for a good run.

2. Many people start the run too fast, You feel "slow" but actually due to having legs in motion on the bike and heart rate elevated are often moving faster than you think. Consciously try to keep a relaxed pace for the first km or so as your get your "run legs". Your first km should be at, or a little slower than, your planned overall pace for the run leg. It shouldn't be way faster.

3. Learn to drink on the bike. If you have a trainer, practice on that first, then practice in training. Your discomfort might be due to dehydration, coupled with what you're drinking (see below). You can learn to drink on the bike. I'm possibly the world's klutziest person, and I've managed to teach myself to drink from either mount on the frame of two different road bikes, an aerobottle on a tri bike or road bike, and even grab and replace bottles from a rear mount on a tri bike. It's doable. Practice, practice, practice. Doesn't always make perfect, but at least semi-acceptable!

4. Not sure what's in your drink, but if it has large amounts of sugar/caffeine, that might be hitting you particularly hard when you're hot and dehydrated. (I'm visualizing myself, dehydrated and overheated in a tropical race, taking a huge swig of Red Bull in T2. Results would NOT be pretty!) For a sprint or Oly, you mainly just need fluids and electrolytes. Try a drink with less/no sugar or caffeine like Nuun.

hydrating for the run is too late. if you're going to hydrate in T2, just accept your going to have to slow down a little. By taking off and running fast, your body is probably not even absorbing what your'e drinking.

Experiment with using water only (or water & electrolytes only). You don't need calories for a race that short. if you're training longer than 60-90 minutes (you mentioned 15k running) then yes, but not for a sprint.

You could be experiencing a medical issue that should be identified or ruled out as soon as possible with a racing heart under certain situations. Stress & Dehdration will certainly make that more likely so see a doctor before your next race and preferably before your next training session begins. Just take a week off to get in to your doc.

Thanks all, some things to think about there. I did go and get checked out before I started any training, got hooked up to a heart monitor and stuff, there wasn't anything of concern. Probably wouldn't hurt to go again though.