# Progression of heart rate over long distances.



## z3phrn (Mar 19, 2011)

I'm trying to figure out why my average heart rate drops as an endurance event progresses. Is it physical fatigue or possibly lack of experience/base miles? I didn't _feel_ that tired at any point, and wasn't in any pain or anything. I also tried to keep a decent pace and maintain the perceived level of exertion, but my heart rate definitely drops in large chunks as time went on. I've read a couple of the more famous endurance riding books, but there wasn't much about the progression of heart rate over the long distances, so I'm just trying to quantify what happens physiologically.

For the death ride, I completed the first half with an average heart rate of 160 (zone 3), which is pretty standard for me. However, as I approached the second half, the average dropped down to 150, and towards the third quarter, it was hovering around 140. By that point, I could barely get it above 150. 

http://connect.garmin.com/activity/98113509
[ignore the crazy spikes in heart rate, as usual]

One theory I have is due to the long breaks I took while waiting for a friend (who we later noticed had rear brakes rubbing pretty badly). Is there supposed to be a significant change in performance after something like a 30 minute stop?


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## Cableguy (Jun 6, 2010)

Sounds similiar to what I've experienced, I think it's normal. As you fatigue over a long event your ability to reach a high heart rate decreases and at the same time your minimum heart rate rises as recovery becomes more difficult. On your graph you can see the HR line *flattens* out more towards the last half, indicating that recovering from efforts was harder for you than when you started out. Also, you can see your HR peaks less notably the second half than the first - ignoring the massive HR spikes from going 30+ mph (you may want tighten your HR strap!).


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## Marzo92 (Apr 15, 2010)

I see the same thing the few times Ive been to 6 hours, higher heart rate first half vs second.

Question along the same line - 

What should my heart rate be on a long event? 51 yr old, 175 max by prolonged (& agonizing) test, 158 average held for 60 minutes per heart rate monitor. For a 6 hr century plus or minus, 140 average? 150 average? Any guidance or rule of thumb?

Thanks.
Marzo92


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