Easy versus Hard

A fantastic thread discussing the relative merits of high volume/low intensity (ie long, steady rides) versus lower volume/higher intensity (ie SST/Threshold) training.

It is seriously worth signing up to Google Groups Wattage forum anyway – especially if you’re interesting in training with power.

Anyway, this particular thread is here.

I’ve made no secret that, especially given my newly imposed time constraints, I’m going to opt for the latter (ie a relatively low volume/high intensity) strategy.  This is largely contrary to the advice of most coaches and not to mention a considerable tradition which suggests ‘getting the miles in’ to ‘build an endurance base’ is the way forward.

It would be nice to say that ‘we’ll see’ which is the most successful strategy but with so many confounding factors we probably won’t.

Power vs Heart Rate Metering

I did some science today.  Like most ‘sports science’, it wasn’t very good science.  But it was an experiment of sorts.

I’ve been banging on to anyone that will listen about the benefits of power meters in general and the PowerTap in particular all year.  I’ve used mine this year to gauge my indoor training efforts which have largely consisted of threshold work (2x20s, 3x20s, hour of power, etc). 

One of the many reasons (don’t get me started…) for using a power meter is to accurately gauge the work that is being done during an interval.  Intervals consist of a target intensity, duration and rest period.  Traditionally the intensity has been monitored using a HRM (heart rate meter).  The problem with this is that heart rate is subject to many confounding factors – fatigue, dehydration, temperature, caffeine and so on, all have an impact on heart rate  which makes it only a so-so guide to the intensity of the effort that is being made.  The response of the heart to effort is also considerably ‘damped’; ie it takes a long time to catch up with any changes of intensity.

Anyway, to my wonderfully unscientific experiment.  My hypothesis is that the power, and therefore work, would vary considerably across an interval for a consistent heart rate and vice versa.  Initially raising the heart rate would take a deal of effort and as the interval proceeded fatigue would mean that, in order to maintain a consistent heart rate, the power would need to decline.

I was planning a 3×20 ‘sweet spot’ session.  Using power as a metric this corresponds to about 290W.  Using heart rate I estimate this would be about 160bpm.  My plan was to do the first interval based on power, and see what happens to the heart rate, the second according to heart rate (159bpm +/-1) and the final interval back to power again.  Here is the result…

3x20

(click to image to see full size).

NB Heart rate is shown in red, Power is yellow.

It is worth bearing in mind is that, even indoors with the absence of wind, hills, junctions and so on, it’s not possible to maintain perfectly consistent power output.  Despite this I hope that you can see that the first and third efforts are reasonably consistent.

The first interval is very interesting.  I only warmed up for 5 minutes (coz I’m ‘ard) but even so, you can see that my heart rate climbed throughout the entire 20 minutes and took 5 minutes before it even reached 150 bpm let alone 160.  So the first 20 minutes displayed a totally non-linear relationship which is what I had expected (and, yes, hoped for!).

The second interval was done with a consistent as possible heart rate, targeting 159 +/- 1 bpm.  I did not want to exaggerate the initial effort so I tried to slowly build for a minute or so into the interval.  Either way you can see that the initial power was high, and quite fatiguing, and did slowly drift downwards through the remainder of the session.  But not to the extent to which I thought it would have.  Given the non-linearity of the first interval, the second I found surprisingly consistent.

By the third interval I was back to consistent power and again the heart rate response was variable, slowly building throughout the entire 20 minutes but much less than the first interval  – presumably due to my inadequate warm-up.

Summary

It should be noted that this was a generous test from the perspective of heart rate – the intervals were neither short nor massively intense.

What I hope I have shown is that

  • There is not a linear relationship between effort and heart rate response
  • Even working reasonably hard (90% of FTP) it can take 20 minutes, or more, for the heart rate to level off
  • Due to this latency, it is likely that using heart rate as a guide to interval intensity is likely to lead to starting too hard leading to unnecessary fatigue. 
  • If you are using a HRM to gauge interval effort a proper warm-up is a good idea
  • I found the second interval the hardest, most probably because of the 310W + required to get my heart going

Tour of California Power Profiles

One of my rare indulgences (!) has been to equip my ‘training bike’ with a Powertap, which looks a bit like this

Measuring power directly is the new heart rate monitoring.  It allows a cyclist to gauge accurately the actual work that he (or she) is doing, rather than the bodies response to it.  Cyclists (and runners) have been monitoring heart rates for years but it does not vary linearly with effort; the effects of fatigue, caffeine and the excitement of an event all have an influence.  There is also a considerable lag between an effort and the body’s cardiovascular response.

Why measure power?  Well, for at least three reasons.  First, it can be used to accurately target training efforts, especially intervals.  Second, it can be used to gauge progress and get feedback on the success, or otherwise, of whatever training regime you are using by letting you precisely calculate useful metrics (eg, FTP more of which is later posts).  Third, it’s a very useful pacing device, for instance on  long climbs or time trials, to make sure that you don’t burn out early or simply sell yourself short.

Now there’s a fourth reason.  Gustav Larsson is going to posting his daily WKO (software to view and analyse power files) files from his rides in the Tour of California so we can see what the pros manage to ‘put out’.  My best 5 minute power, though I’ve only ever recorded one effort, was around 420W.  In the prologue, he managed 529W for just under 5 minutes.  And he didn’t win!

You can view them here.