Heart Rate Vs. Power Zone with Climbs & Leadville 100mtb

Long time listener, first time caller. Confusion and concern with heart rate zone vs. power zone. There is a lot of information on this form and the web, but non specific to my scenario. Seeking recommendations, directions, tips, tricks etc.

I am a 40yr male, mid-pack MTB rider, completing a handful of distance XC races in Colorado. Currently utilizing a trainer road program in preparation for Leadville 100, but I have started to deviate with some longer outdoor rides and big hills at elevation for specific race prep. This weekend I road 33 miles, in 3 hours, with total ascent of 3,550 feet, at 7,200 - 9,500 feet elevation. NP of 207 W and max avg of 254 W. 248 FTP setting. Avg cadence 71. Avg. HR 161 bpm. Avg. Respiration 36 brpm.

The Concern = Yes this was a ass-kicker of a ride, but I was shocked to see 57% of the ride, my heart rate was in zone 5 (162 bpm +). But only 31% of the ride was I in power zones 4 (223+) or above. 25% of the ride I was in zone 1 power, but I contribute that to the descents. Last years Leadville I did a great job maintaining Zone 3-4 HR for 95% of the race. Very concerned with my time spent in Zone 5 vs. the power output this weekend. During the climbs I consistently found myself at 178 bpm+ and was trying change my breathing and cadence to reduce.

The Question = Confirmation my delta between heart rate zone and power zone isn’t ideal and what can I work on in the next 40 days and when racing, to get my heart rate under control for Leadville 100 mtb.

Side Notes: I live at 7,200 so the elevation shouldn’t impact my HR as much as others. This was my largest ride, after taking 3 weeks off in June for a honeymoon, where biking wasn’t available, so I expect to see an immediate increase to fitness and FTP the next four weeks with my regular training. I use a Garmin Edge unit, Garmin hrm chest strap and sram axs power meter, so I trust the data I’m receiving.

Thank you all for the recommendations and direction. Advice to decrease the delta in Power to HR, along with HR strategy when riding is greatly appreciated.

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Congrats on the recent marriage and wow, a 3 week honeymoon! Your HR is almost certainly higher right now because you took 3 weeks off and just coming back.

Is your FTP setting of 248w at sea level? If so pacing by power can be tricky, since you lose so much available power at 7,000-9,000 feet, even when acclimated.

your max average could be as much as 254w/0.863 = 294w sea-level equivalent.

Hey @wallbrenton34!

Welcome to the TrainerRoad forum!

Ooooff, good work!! :muscle:

There are a lot of things that can impact your HR, irrespective of fitness. The first thing that comes to mind at this time of year is hydration. Dehydration decreases your blood volume. To compensate, your heart beats faster to ensure adequate oxygen and nutrients get to your muscles, ultimately allowing you to maintain your power output.

Altitude can increase the risk of dehydration because of the increased breathing rate and thus moisture lost through your breath. Likewise, if the air is dry, you can lose more fluid through your skin.

With that in mind, have you dialled in your hydration for these longer rides?
You can experiment with more fluid and electrolytes, to see how that impacts your heart rate?
You might also consider a sweat test to ensure you’re getting it right.

Furthermore, is this something you have noticed over time or was the weekend the first time you’ve noticed it?

The reason I ask is that a host of factors may temporarily impact your heart rate, such as fatigue, stimulants such as caffeine, lack of sleep, sickness and time of day you train. While your heart rate can be helpful as feedback on some of these variables, it might not be a reason to be concerned, granted you listen to that feedback and adjust appropriately.

Do you think any of these factors could be at play?

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After 3 weeks off, I would expect a big jump in HR at similar level of exertion. I wouldn’t read too much into it until you get a few weeks into your new training block.

That said, I’m personally not a big user of HR data in general. I find it to be all over the place depending on fatigue, fitness, fueling, temp, humidity, altitude, hydration, caffein intake, etc… The only time I’ll wear a HR strap is indoors under very controlled situations and even then it’s more for curiosity. I’ve never taken a HR strap to leadville, I honestly wouldn’t know what I’d do with the data. Even coming from sea level, I’ve been to altitude enough to know what power numbers I can do for a given time and my respiratory rate is almost always my primary governor when in the high mountains. I’m not saying HR can’t be of value for some, but I personally found there are too many things swinging it around for me to get value from watching it.