So here's what happened. Today I went for a nice 230km ride, not the first one and almost certainly not the last. The thing was, at Brunswick Heads on about 130km I paused at the local bakery for some refreshments, a couple of bread rolls and a drink, the same as I always do. Shortly after this, while riding out of Brunswick Heads on a totally flat road with a tailwind I suddenly felt my heart-rate go really high, I mean to dangerous levels. I didn't look at a HRM (I don't have one) and I didn't need to, I could literally feel it in my chest.

At that moment I came to a complete stop and pulled off the road immediately, having absolutely no idea what was going on. A few seconds later, I had calmed down and was able to continue on and complete the ride as normal (albeit a little cautiously).

At this stage I have no idea what happened or how. I do know of the effects that heat can have on one's heart rate, but the massive southerly wind kept today's temperatures well down for this time of year, and it couldn't have been more than about 28 C. At the time it happened I certainly wasn't working overly hard (and nowhere near as hard as I had worked going against the wind earlier).

Could it be something as simple as what I ate, or might there be more to it than this?