Saturday, 16 May 2015

Heart rate and training - revisited

StravistiX chart of my recent "century" ride
- how can I have a heart rate of 110%?
Last Sundays "century" gave me some good data to have a look at/
The route I rode is the "actual" route I will be riding in just over 3 weeks time.

For those of us without Strava Premium, there is a handy utility called StravistiX, which is available as a "browser extension" for the Chrome browser. It adds an extra "button" to the standard Strava screen which allows "extended statistics" to be shown.
Extra statistics and graphs are then displayed from the ride/run data - the more sensors you have, the more data it can display.
Me, I only have an HRM belt, and of course a GPS device. But StravistiX will also display info from power meters and cadence meters too if you have them. Food pods if you have one, etc., etc.

Anyway, one puts in one's heart rate data and up come some nice bar charts and some stats.

But what heart rate should one use?
the highest heart rate I have come measured for myself is 181 bpm - uphill, and I failed to complete the hill because I "ran out of steam", and it was after I had done a circular course with the hill a few times, so my HR was ratcheting up.
I find if I am tired, i just can't push myslef hard enough to get up to that high a heart rate!
So my Max HR is 181 bpm, right?

Except when I put that number into StravistiX I get the chart at the top of the page.
Fine, except that the 2top" band ends at 110% of my Maximum Heart Rate.
Ask a doctor - that doesn't happen. Maximum is maximum!

Which brings me onto the strange idea of "sport-related Maximum Heart rate".
Apparently, because running uses more muscles than cycling, a person can achive a higher "maximum" heart rate while running than they can while cycling.
So the idea of a different maximum heart rate for different sports came about.
To the theorist, it is, of course, complete rubbish.
Just because a sport can't normally stimulate you enough to reach your "true" "maximum" heart rate doesn't mean that particular biological limit has changed at all.

But, nonetheless, it is an idea that has gained quite a bit of traction for it's "functional" aspects.
What percentage of my "functional maximum" heart rate can I achieve, is perghaps the question then?

Well, the highest heart rate I have achieved while cycling is 172 bpm, and just like the various suggested ways of getting up to your maximum "functional" heart rate, it was at the top of a significant climb that had three distict phases - two short, sharp slopes, just to "soften the rider up a bit", and then a longer climb of varying gradient, finishing 170 metres above the start (the gradual gradient of some of the parts means it doesn't qualify for a Strava Cat 3 climb, although the later part of the climb qualifies as a Cat 4 climb!). So it was a long climb that ratchets up the heart rate!

So, if instead of my "true" maximum heart rate (181 bpm) which was achieved by running, what happens if I use my "functional cycling" maximum heart rate of 172 bpm instead?

"functional cycling" maximum heart rate of 172 bpm

"true" maximum heart rate of 181 bpm
Look what a difference that makes to the stats!
The various "quartiles" for heart rate don't change (it was the SAME HR data I used for both charts!),
the "toughness" doesn't change (which is only right and proper, becausee the data is the SAME DATA FROM THE SAME RIDE), but look how the "Training Impulse" has jumped from 496 to 581.
Training Impulse is calculated in a similar way to Strava's "Suffer Score", so by using a lower maximum heart rate, it appears I am doing more training!

And yet the same set of ride data forms the basis of both graphs!

So the "true" training MUST be the same!
I think that the StravistiX charts must be expecting me to use my "functional cycling" maximum heart rate, rather than my "true" heart rate, as then the ability to get 110% of "maximum" heart rate is no so impossible - indeed, a figure (at 100%) of 184 bpm is not so far from my "measured" (running) figure of 181 bpm.

Just think about this, though.
Next time you side a rider achieve a large "Suffer Score" in Strava, think about whether that rider has made the same heart rate assumtions that you have.
Have I training in the "top zone" for 29 seconds, or have I trained in it for over 4 minutes?
The two graphs both suggest one of the answers, but clearly they can't both be "right"

On a more practical note, given the length of the ride I ahve a bit more time in the 140 to 150 bpm region that perhaps I should - I faded rather badly towards the end. I had the "Heart Rate" alarm on my watch set to 150 bpm, and only passed that on hills.
I think I ought to move that down to 140 bpm, so that I conserve my strength a little more for the later parts of the event!

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