I'm trying to figure this one out. It's difficult.
The chart at right shows my heart rate (red line, at top) and the speed at which I'm running (blue line, at bottom). In both cases, up is faster.
Ignore the weird jaggies in the blue plot. The GPS track isn't super-accurate when I'm running under trees—the important part here is that I'm running at a pretty constant pace.
Anyway as I start running, my heart rate comes up until it hits 162 or so, and then it falls back down below 160. And here's the weird part: when I slow down, my heart rate spikes to just over 170 and then falls off.
I have no clue why this is. Any ideas?
P.S. This happens with two different heart rate straps and two different monitors, so it's unlikely to be a production flaw.
Can you plot altitude on that graph as well? Perhaps you are slowing down because you're going uphill. That would surely cause your heart rate to spike even though your speed is lower.
I can, but this was all pretty even, and I get the heart rate spikes even on completely flat terrain. Steep grades would definitely bring my heart rate up when I stop running.
During a run on Saturday I did notice that I usually slow my breathing considerably when stopping, so I'm guessing now that the decrease in respiration may be the cause.
--D