Just wanted to revive this old topic. I do ultra endurance/audaxing, and I’ve noticed that my heart rate drops a lot several hours into a ride. For a while I’ve been thinking that just means I’m exhausted and slow, but on the 34 hour ride last weekend, I looked more into it.
For example, if I average 170 W 2 hours into the ride, my heart rate is quite high at 147 bpm. After 8 hours, my HR is 145 bpm even if I do 177 W. And then, after 28 hours, I’ved eased off a little to 158 W, but my HR is only 123 bpm!
This seems like a significant negative decoupling. Has anybody experienced something similar? I wonder what the physiological explanation is.
