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FAQ ~ Power or Heart RatePower v Heart

When undertaking your sessions, you have power numbers and heart rate numbers.  Is it better to stick to the heart rate or the power figures, I cannot do both at the same time? 

Here's my data from my Tempo 10, should I hold the power and let the heart rate go up, or hold the heart rate and let the power go down?
Sašo Prijatelj ~ Slovenia

Probably one of the most asked questions, and most troubling of conundrums for most riders when they get a power meter.  It doesn't take long for the clever riders to spot the disproportional relationship between these two metrics.

I'll answer Sašo's question directly and cover the why's and wherefores in a little more detail, to help others get a better understanding of where I'm coming from.

I never have, and never will, provide heart rate targets for training.  All of our programmes have them, because it's what riders want and expect.  Doesn't make it right though!  Which is why we have programme warnings everywhere to only trust your heart for reasons of love...

To answer Sašo's question quickly; its power. 

srmAlways ride to power if you have it.  If you don't ride on perception (or use turbo speed) and make sure you just get to the end of each session. 

If you just make it to the end of the session, whatever the figures, power, heart, speed or otherwise, you will have ridden your best, so what more could you have done?

Figures in our programmes are derived from the information returned to me in our comprehensive physiological questionnaires.  So we (and you) rely on that information being accurate.

Sometimes riders have a pre-programme, performance evaluation to get "their numbers".  But the figures between a calibrated, power measuring ergo, can differ vastly from your personal power meter, turbo, Trainer Road or Strava's "estimated power".

Some, also use their season's best figures for max heart rate or FTP.  The max's you gained in July and August can be a far cry from what you are capable of in the depths of winter.  SO make sure your baseline metrics are recent, relevant and accurate.

Also the way "analysis programmes" drop heart rates in to "bins" to summarize a session can be fundamentally flawed.  Here's a session from Jersey lady Kat Guillemot...

First here's her Speed, Power, Heart and Cadence traces...


All looks good, and tracks Sašo's session (top) pretty accurately for heart rate


tempo ten

Tempo Ten Power Summary ~ perfect!

In this graphic, you can see an 8% drift in to Threshold Power, accounted for by the perfectly timed "testing the boundaries" towards the end of the last ten minute effort.  It also shows how spectacularly accurate the ride was for the rest of the Tempo Ten efforts!

The Z1 & Z2 bins made up of the warm-up, cool down and recovery in between the tempo efforts.

Now here's the exact same session, in the exact same programme, rated by Heart Rate...

hear rate

Heart Rate 50% Threshold ~ Really?

So you can see from the above that something is patently, not right!

Now Kat had, just two weeks before, undertaken a Ramp Test to ascertain her "vitals; she's smiling because this is her warm up...

Kat G

So we know her numbers are as accurate as can be.  So why the heart rate discrepancies? 

There are all sorts of reasons, heat build up, cardiac drift, oxygenation of the blood, quality of the warm-up, time of day, caffeine ingested during the day, hydration, de-hydration, I could go on, and on, and on...

It could be that Kat has the wrong numbers in her Strava set up; but she hasn't.  Or it could just be, from the heart chart above, that Kat drifted from 170 bpm (Zone 3 Tempo HR) to 171 bpm (Zone 4 Threshold HR). 

So the whole thing is thrown in to confusion as we now have a Tempo session run at 50% Threshold effort.  How absurd!

Once you have power measuring capabilities, all your work should be driven by the power metrics.

Power is a scientific number, a watt is a watt.  Heartbeats are all over the show! If you want to liberate yourself, and improve your riding, lose the heart monitor! 

Use it for amusement, or get the correct numbers and use it to monitor progress, not drive it.

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