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…


(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.


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

Awesome Fixed Gear Riding

One gear No idea from chris akrigg on Vimeo.

Winter Bike Dilemna

Another year the same problem; I really want a bike with full-length mudguards for practical reasons.  But I also really don’t as full-length guards are aesthetically so wrong.

SKS race blades offer a compromise but they neither look great or work that well.  However, maybe these bad boys might just do the trick?

(edit – review on road.cc)

Tour of Ireland 2009

Those suffering from withdrawal symptoms after the Tour de France will be pleased to see that ITV are covering the Tour of Ireland again.  The schedule is as follows

Friday 21 Aug

Stage 1 highlights, ITV4, 7pm

Saturday 22 Aug

Stage 2 highlights, 8pm, ITV4

Sunday 23 Aug

Stage 3 highlights, ITV4, 7pm


Both Armstrong and Cavendish are riding as are some of the top British pro teams (Madison, Rapha, Halfords, etc).

(edit – apologies for the obvious missed gag.  Alan Partridge would have said “there’s tour of ireland dan dis”)

Result for Bigfoot and AndyC

How about this for a fantastic result?  AndyC won the 3rd/4th category race at Crystal Palace last night.

Respect and congratulations.

The official report is here.

Respect due…

And apologies.

After the King of the Downs ride I boldly stated that photographic evidence showed that Miss Jo Munden was not, in fact, a woman (in third place below).

It turns out I was wrong, as she has just emailed me!

So chapeau to Jo.  And sincere apologies from me.


I don’t really do embarrassment, however this made me blush…

Liege Bastogne Liege 2009

The LBL is my last scheduled ride of the year so it was important it was a good’un as it marks the end of my season to all intents and purposes.

And on paper it was going to be.  Not least as the pro event is one of the five ‘monuments’ of the sport and the oldest of the ‘classics’ as it was first run in 1894.  The race route runs from the unglamorous town of Liege to the unglamorous town of Bastogne and back again; a flattish 95km there and a hilly 163km back.


As you can see DaveC is looking good but Liege is doing a mighty fine impression of Croydon!

Oddly the amateur event is organised by the Dutch largely for the Dutch – in Belgium.  The route was either 235km, 245km or 260km depending on where you looked and there where no reliable maps or GPS downloads available from the organisers website.

The ride normally has an entry limit of 5,000 riders but this year this was cut to 3,500 and I think that the normal route was revised.  Both of these changes were down to the ‘local councils’ in Belgium – I think.

The ride kicked off at 06:00.  That meant setting the alarm for 04:50 which felt like 03:50 as we’d lost an hour due to the time difference.  I actually awoke at 04:20 and decided I might as well get up anyway.  I tucked into a nice plate of fruit laid on by the hotel and set about trying to find enough places to hide energy bars, powders and gels to fuel myself for the coming 9 hour marathon.

We made our way to the start in the dark which was a couple of kilometres from the hotel.  It became obvious that the bulk of the 3,500 riders had not opted for the longer route.

Off we set.  No timing chips.  Instead they had a card-stamping operation.  DaveC got his card stamped, I hadn’t even bought mine along.  We navigated our way through the town with the help of fellow riders.

I was not able to get a route for the Garmin for the ride so it was important that the signage was good.  Which, in honesty, it was not.  Don’t get me wrong – I do not underestimate the effort required to sign a 260km/160 mile route.  The signs were too small and often were only visible when you were right on top of a junction.  By the end we missed 4 turns; two trivial, one relatively minor and one worth about 10km including a massive climb!

We found a couple of Dutch guys that were setting a reasonable pace on the early climbs as we dropped the rest of the early starters.  We ‘sat in’ for a bit until I decided that I should do my bit.  Which was weird as as soon as I got to the front the Dutch chaps seemed to deliberately fall back a few metres – seemingly unwilling to take advantage of my un-aerodynamic clearing of the way.

The weather was, well (Belgian Tourist Board look way!), shit.  Coming from the UK saying this means something.  It was like a ‘warm winters day’.  A horrid mist persisted for the first 6 or 7 hours of the ride.  It was wet, the roads were wet and it was just a bit dismal all round.  A times it felt like we were cycling through a a scene from Lord of the Rings.  There seemed to be miles of quiet roads through bogs and fallen trees.  Visibility was very poor.

Contrary to expectation the first part of the ride down to Bastogne was really hilly.


(Apologies for the missing legend – miles on the X axis, elevation on the Y axis)

At one point DaveC lightened the mood (or rather lightened my mood) by saying “this is like torture”.  Endlessly climbing with no end in sight.

The feed stations, if not brilliantly stocked were at least frequent – every 50km or so.  I think Henry Ford was in charge perhaps as the options were a tad limited.  The first offering only a (albeit delicious) waffly, caramelly biscuit thing for sustenance.  The second yoghurts and rice pudding.  By the time we got to the fifth there were thousands of people around with 10 minute queues just to get tap water and only ‘tuc’ biscuits and bananas to eat.

And so the ride ground on.  We couldn’t see that much beyond the misty bubble we inhabited.  In some ways the ride reminded me of long turbo sessions.  When you ride for an hour indoors time really seems to drag.  Doing a two hour session in some ways is easier, because it feels like there is no hope.  And without hope there is no disappointment.  Still, the poor signage kept us alert – at every junction we meticulously scanned every sign to make sure we hadn’t missed anything.

We did do a couple of impressive climbs both in terms of length and gradient.  By this time we had caught the riders doing the shorter routes and they were doing a terrific job of boosting my morale.

La Redoute was terrific and is the ride’s last most famous climb where attacks normally take place that can decide the outcome – for the pros that is.  Three times I was lulled into thinking the climb was coming to an end by the presence of spectators and put on a bit of a show, and twice I was wrong.  When I say ‘put on a show’ I mean humiliate myself by thrashing around all over my machine like the mediocre old man that I am with 230km on the clock.

And so the ride finished.  I was amazed how good I’d felt throughout the ride.  It was the by far the furthest I’d ever ridden in one go (by at least 50km) and I felt really good throughout.  I was concerned that my seemingly good endurance would dessert me but I held on really well until the end.  (edit – I should point out that almost as soon as the ride was over I was completed fucked :-) ).

As ever it was a pleasure and an honour to ride with DaveC who, in his un-pushy and modest way, has done so much to encourage and educate me over the last 18 months.  He’s not the club legend for no reason!

Some stats
  • Ride time – 10 hours (!)
  • Length – 260km
  • Climb – 4,200 metres
  • Full stats
Good things
  • The Dutch – how did they get to be the cool ones?
  • 160 mile ride – awesome challenge
  • My sore legs the following day – it’s nice to be reminded :-)
  • La Redoute
Bad things
  • Signage
  • Route – what happened to the famous climbs in the second half
  • Feed stations – charge me €30 instead of €15 and get some good stuff in!
  • Belgian weather – even we’d turn it down
  • Organisers website/lack of information
  • Lack of timing chips

DaveC summed the first part of the ride up more succinctly that me here

“As we climbed the hills surrounding Liege, daylight revealed mist/drizzle covering everything, reducing visibility to about 100 metres. This torture continued for several hours, with the road ahead always climbing towards an invisible summit followed by brief descent then up again.”

CycleOps Pro 300PT Spin Bike

Well, with a baby on the way some compromises need to be made.  Not least a clearing of the second bedroom for it’s conversion into a nursery – the cheek.

My indoor training is going to be relegated into the third bedroom amongst other inconveniences (god I need a garage!).  The best solution seems to be to get a spin bike, and this cheeky chappy seemed to best fit my needs.


It’s made by the same guys that make the PowerTap and has the same facility to download the workout data into the excellent WKO+.  It should be much quieter than the turbo and it has a 25kg flywheel so should ‘feel’ better too. 

This then frees up my Trek bike to become my official winter training bike, complete with PowerTap.  Which frees up my titanium winter bike from last year to be sold on eBay.

The last big advantage is that the power data for all of my riding (indoor and out) will be downloadable.  CTL and TSS – bring it on!

The biggest fear – the same fate befalls it as the vast majority of indoor trainers; it becomes a very expensive dirty clothes rack!

London Triathlon Afterword

Well, the results are in and the official photographs are available online.

The good news is that I was the only finisher in the top 20 that was on a regular road bike (even my ego couldn’t drive me to check any more pictures!).

The bad news is that I still look a dog’s dinner on the bike.

The countdown begins to the Liege Bastogne Liege this weekend…