# LT HR at altitude vs. S.L. for acclimated rider?



## spiffomatic (Jan 28, 2010)

Lacking the funds for a power meter for now, I'm looking to establish my HR zones (using Friel's training bible for the most part) - have been going off of ballpark estimates from years past for now (mostly Z1/2) since I didn't want to do an all-out 30 min effort in early base training. His method suggests pegging your LTHR with a 30min all-out time trial, taking the Avg. HR from the last 20 min and using this as your LTHR. As I get out of Z1/2 riding into more Z3+, it seems like it would be more critical to not be 5-10 beats high or low for planned efforts. I'd like to do one of these 30min tests later this week and here's my question:

I haven't seen much info on this topic, but for a fully acclimated rider, can one expect to have about the same LTHR (not power, of course) at altitude as at S.L.? Due to work, I find myself having to split training time often between 8-9k' and S.L., with most of the time at elevation. I know can eventually find my own answer to this by doing a 30 min effort at the two elevations, but again, being in the base period, I'm not inlined to thrash myself too often until a bit later into the training cycle, so it would take some time to get to the bottom of this.

Part two to the question is, if there is something of a difference in LTHR, am I better off finding my LTHR with a 30min test at S.L. or at my more typical altitude? I think that at this point in the season, my cardio stronger than my legs due to cross training and more time spent at elevation - i.e., some of the aerobic threshold (Z2) efforts Friel suggests feel tougher on the legs than cardiovascularly when done at S.L. - so I wonder if I wouldn't be able to sustain LTHR for 30min at S.L. until later in the season, and would find a HR that's too low during the test...

Thanks for any input!


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## MontyCrisco (Sep 21, 2008)

Altitude does affect heart rate. You don't mention how big an altitude difference you are dealing with, but in any case I think the solution probably does involve calibrating your zones for different conditions. Like, heart rate is imprecise enough that worrying about other sources of imprecision is just going to make you worried, whereas this factor alone is unlikely to matter *that* much. It's similar to what we have to do for cooler vs. hotter seasons, where again you tend to see lower HRs when the outside temp can help you keep cool. It's just something you have to accept as a pitfall of training with HR.

To answer your second question I suggest you do the test at the altitude you tend to train at the most (or perhaps, the alt. at which you're more likely to be doing z3-z4, which tend to be the ones that are hardest to dial in IMO). Go back and re-test periodically (say after 6 weeks?) to make sure you got it right the first time. Adjust accordingly. Monitor your RPE and if you do think that a certain HR level feels too easy or too hard for the effort level, trust your instincts. 

About when to do the test:



spiffomatic said:


> have been going off of ballpark estimates from years past for now (mostly Z1/2) since I didn't want to do an all-out 30 min effort in early base training.


There's no reason to think that 30 minutes in z4/z5 is going to ruin your base training. The worst it'll do is make you too tired to do a long z1/z2 endurance ride the next day. So just schedule your test days for rest weeks where you are putting in fewer miles anyway.

More generally: I have heard some people claim that doing z4 during an endurance workout ruins the benefit that you got from doing all those z1/z2 miles. I think that's wrongheaded (yes, speaking as someone with zero training in sports physiology). It just limits how many long steady miles you can put in.


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## spiffomatic (Jan 28, 2010)

Thanks for the input. I think you're right though... if there are differences, they're small and I'm probably over-analyzing things that aren't that significant. It's about an 8-9k ft spread between elevations but I'll just spent some effort at LT at both high and low and see what comes of it.


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## multirider (Nov 5, 2007)

I'm very interested in this topic -- I train at 6,000 feet and often race at 9,000 to 10,000. I've found that I cannot hit the same heart rates at the higher elevation. But I'm not sure if that means all my zones shift down or I simply can't get to Z4 or Z5 as easily and can't stay there as long. For shorter races, it doesn't really matter because I just go all-out. But for longer races, it would be helpful to know. It is certainly harder to recover from Z4/Z5 at higher altitude. Should I be adjusting the definition of my zones down a few beats? If so, any ideas on how many would be welcome!


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## MontyCrisco (Sep 21, 2008)

How about doing your LTHR test at both the altitudes you train/race at? That would give you two sets of HR zones, one for 6k feet, the other for 10k feet. 

(And yes, I'm sure someone will chime in soon to tell us that using HR is useless and we just need to buy power meters  )


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