Translating FTP to heart rate

I've been trying to advise a fellow rider about why caning herself with the morning group is probably not such a good idea and that she might be better off working on her aerobic engine.

Now, I can tell her about FTP and watts, but she only has a HRM. My question is: if she does a 20 minute FTP test, would I take her average heart rate and subtract 5% like one does for a wattage reading?

I'm trying to talk her into the benefits of a power meter but in the meantime I need to be able to advise her on using heart rate. Training and Racing with Power has heart rate zones but the book doesn't seem to specify what they are percentages of.

Any help would be appreciated.

The book would reference HR at TT power (which of course is variable) as the anchor point - say avg of the final 20 min of a TT. Others calculate zones as % of Max HR.

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Thought so. So I'll get her to flog herself for 20 minutes, take the average HR and use the zones as a percentage of that figure. No subtracting 5% or anything like that.

Thanks Alex

Note that Alex said average HR for the last 20 min of a (40 km) TT.

I'm sure the average over a 20min time trial will probably be sufficient for our purposes. We're shooting in the dark as it is using HR instead of power. Unless my colleague wants to do a 1hr TT, that is.

There are numerous threads devoted to the best way to determine FTP and I'm sure whichever method is used there'll be problems highlighted.

What we really need is a Power Tap or SRMs, but as this is very much an ad-hoc exercise designed to illustrate the fact that taking a weekly caning is not the best way to build fitness, the margin for error is not that important.

If she gets more serious then adjustments can be made, but until then, near enough is indeed probably good enough.

From personal experience I can confirm that is not the case. My heart rate does not reach its peak until much later into the TT. So, taking the average over the last 20min of 1 hour TT is more reliable estimate.

Training by heart rate outside (i.e. not on an indoor trainer) is not as reliable as trainig by power, heart rate reacts much slower to higher power output.

FWIW, I actually based the guidelines on average heart rates across the entire 40 km. Given the 'slop' involved, though, I don't think it really matters.

Just as it takes a while for the HR to initially respond it may be that the last 20 min average may be artificially elevated due to dehydration or an all out finishing effort. So, averaging over the full 1hr (or 40K TT) may be the most accurate.

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I agree knowing my average HR over a full one hour TT was very useful to me for HR based 3x20s.

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