Calculating FTP without a powermeter.

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Calculating FTP without a powermeter.

Postby Arlberg » Thu May 30, 2013 7:47 am

I don't have a powermeter, and I'm sure many other readers don't either.

Is there a way to test for FTP without using a powermeter? If there is, is there then a way to then train effectively in the various zones without having a powermeter to measure the % of FTP being produced?

For example, if I want to train at 85% of FTP for 20 mins , can I do it without a powermeter?
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by BNA » Thu May 30, 2013 8:54 am

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Re: Calculating FTP without a powermeter.

Postby Aussiebullet » Thu May 30, 2013 8:54 am

No, no and no, unfortunately.
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Re: Calculating FTP without a powermeter.

Postby Ross » Thu May 30, 2013 11:19 am

Can't you do it with HR?
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Re: Calculating FTP without a powermeter.

Postby Gassy » Thu May 30, 2013 11:55 am

If you want to train indoors, TrainerRoad is not too bad, using 'virtual power'. You'll need a compatable indoor trainer and an Ant+ dongle/ sensors. the results won't be perfect but they will be relatively consistent. I've been using it for a month or so and it's helped me get an understanding of FTP and training with 'power' and what it's benefits are.

I've just lashed out and bought a powertap hub, so soon i'll be on the road with real power as well, but TrainerRoad will give you a good starting point.
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Re: Calculating FTP without a powermeter.

Postby Alex Simmons/RST » Thu May 30, 2013 12:08 pm

Arlberg wrote:Is there a way to test for FTP without using a powermeter?

That depends on the level of precision you are after.

With a couple of steep climbs, and maximal performance tests of around 5-minutes and 20-minutes, and with the total mass of you and your bike and kit known, then it's possible to make reasonable estimate, but not with the same precision as with a power meter.

If you don't have such a steep climb accessible, then it get pretty tricky. The main problem ís finding a proxy for power output that is not subject to the influence of many variables (or has the impact of all the variable reduced significantly - which is what a steep hillclimb does, as the force required to overcome gravity dominates the power demand and is nearly linear with speed, and is linear with mass, two factors that are relatively easy/cheap to measure).

Arlberg wrote:If there is, is there then a way to then train effectively in the various zones without having a powermeter to measure the % of FTP being produced?

There are many means by which one can measure intensity of effort, power is just one, albeit the most effective and reliable one.

For example, for general aerobic effort (threshold level and below), then heart rate can be used a guide, as can your own rating of perceived exertion. They have their limitations of course, but for general / basic training, these are fine for the purpose.

For shorter duration harder efforts such as interval work, especially performed at and above threshold, then it just takes some practice to learn how to pace those (most don't realise they start too hard and fade badly).

For sprint like efforts, then there is no pacing other than all out, no matter what you are measuring it with.

The trick with shorter harder work is knowing when to stop.


Another method of estimation is if you use an indoor trainer that happens to have a predictable relationship between the wheel or flywheel speed and your power output (not all such trainers have predictable or consistent speed-power relationships but some do). In that case you can use the speed as a proxy for power, but in order to set training levels, you'd need to know the actual relationship of that trainer between speed and power (it is often not a linear one) and ensure the very same set up is used each time (press on force on tyre, tyre pressures and so on). The most direct means is simply to find out how long you can maximally sustain a given speed for.


There are two things in your question-
- how can I know if I am training at the right levels?
- what's the best way of determining that for me?

Power measurement of course will enable rapid fire answers to these, but that does not mean it is necessary to train well, but it can certainly point out training mistakes fairly quickly and enable corrective action to be taken.

Hence the use of other tools/methods to:
- measure fitness (at least a snapshot every so often), such as time up a steep climb, or visit a coach with testing capabilities/equipment (e.g. I can perform Threshold Power or Maximal Aerobic Power tests)
- set training levels and monitor intensity of effort, such as with heart rate and perceived exertion, but to know under what circumstances these are valid and when they are less reliable or no longer valid indicators
Last edited by Alex Simmons/RST on Thu May 30, 2013 4:06 pm, edited 1 time in total.
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Re: Calculating FTP without a powermeter.

Postby toolonglegs » Thu May 30, 2013 3:20 pm

I used the steep hill method many moons ago... worked out that it was with in 5% once I actually got a power meter.
I also got pretty good at Perceived Effort ( look up the scale for a guide ), although once you have a power meter you realize that you usually had it a bit wrong especially on downslopes etc. I think now that even though I don't have a power meter anymore, after having ridden on one for a while you have a pretty good idea ( certainly within 5% ).
Now I just use Strava on a few climbs that I do often to check my form ( or lack of ) ... though that is more checking my power to weight than ftp, still gives me an idea of where I stand compared to known " form " on previous tests.
Heart rate I don't bother... only any good on longer intervals and I think I pace them just as well without a hrm.
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Re: Calculating FTP without a powermeter.

Postby RomanTheCube » Thu May 30, 2013 3:42 pm

If you don't have a power meter to train with (and test your FTP with) then how are you going to use the FTP once you know it anyway?
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Re: Calculating FTP without a powermeter.

Postby Alex Simmons/RST » Thu May 30, 2013 4:12 pm

RomanTheCube wrote:If you don't have a power meter to train with (and test your FTP with) then how are you going to use the FTP once you know it anyway?

I think it's more about the principles of good training, such as: testing performance ability, setting of appropriate training levels, training in a manner to achieve an improvement in performance relevant for your goal(s), and retesting to monitor progress.
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Re: Calculating FTP without a powermeter.

Postby Arlberg » Fri May 31, 2013 2:25 pm

Some great information there, particularly from Alex Simmons who time and time again provides excellent training advice on this site for free that he is quite within his rights to charge a fee for as a professional trainer. Thanks Alex.

What about sites like http://www.bikecalculator.com/ ? It gives a power output estimate when distance travelled, and time and weight of rider and bicycle are entered, probably not so accurate but perhaps gives people an idea of what sort of power they are giving out. But this does not solve the problem of how to measure power output while actually training, such as riding 85% of FTP for 20 mins which is supposedly a 'golden egg' if this guy is to be believed.....

http://www.flammerouge.je/content/3_fac ... thresh.htm .

Alex, just wondering if the Zones 1-7 on the HR zone calculator on your website http://www.rstsport.com/event-training- ... -zones.htm can be approximately correlated with the Zones 1-7 on the Coggans scale? If they do it may be possible to train FTP, and at a percentage of FTP such as 85% by equating a certain heart zone with an approximate power output?

SRM powermeters have one in a Shimano crankset which would suit me as I have Shimano Di2.

http://www.srm.de/index.php/us/powermet ... e-standard
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Re: Calculating FTP without a powermeter.

Postby cyclotaur » Fri May 31, 2013 3:10 pm

I don't have a power meter or HRM, but I do use a Garmin and upload to Strava. I read somewhere (maybe here) that a good estimate of FTP is to find an effort over 20mins and reduce it by 5%. strava uses ride data plus weight to estimate power output if you don't run a power meter.

So I looked up a long ride where I was climbing hard for a decent time and using the Strava feature 'Best Efforts Table' found the best 20 min power average for the ride (349W or 4.4W/kg). Reducing by 5% gives about 330W or 4.2 W/kg as an estimate of FTP. 85% of 330 is about 280W.

Then looking at Strava's calculated power distribution for a typical ride (up to the Dandenongs and back) I spend about 75% of the ride time below this 85% of FTP level - I'm a bit of a slacker !!
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Re: Calculating FTP without a powermeter.

Postby Alex Simmons/RST » Fri May 31, 2013 5:52 pm

Arlberg wrote:What about sites like http://www.bikecalculator.com/ ? It gives a power output estimate when distance travelled, and time and weight of rider and bicycle are entered, probably not so accurate but perhaps gives people an idea of what sort of power they are giving out.

The best site for such calculations is
analyticcycling.com

The main problem with any estimation of power is knowing the input variables, which for flatter roads are so highly variable that estimates are generally going to be quite imprecise.

Consider that on flat terrain air resistance makes up 80-90% of the total resistance forces, then knowing your coefficient of drag, frontal area, and precise wind vectors are required in order to have a reasonable estimate of power. Those are not constant values, vary wildly across riders, and vary for an individual rider depending on their position on the bike (e.g. on tops or hoods or drops), clothing, air density, and wind of course.

That's why steep hillclimbs are the best bet, because they reduce the sensitivity of the calculations to many of those variables.

Arlberg wrote:Alex, just wondering if the Zones 1-7 on the HR zone calculator on your website http://www.rstsport.com/event-training- ... -zones.htm can be approximately correlated with the Zones 1-7 on the Coggans scale?


http://alex-cycle.blogspot.com.au/2008/ ... ining.html
Last edited by Alex Simmons/RST on Fri May 31, 2013 6:04 pm, edited 1 time in total.
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Re: Calculating FTP without a powermeter.

Postby Alex Simmons/RST » Fri May 31, 2013 6:03 pm

cyclotaur wrote:I don't have a power meter or HRM, but I do use a Garmin and upload to Strava. I read somewhere (maybe here) that a good estimate of FTP is to find an effort over 20mins and reduce it by 5%.

Most people's FTP will be less than 95% of their mean maximal 20-minute power. 95% is quoted as a reference starting point from a specific test protocol suggested by Hunter Allen, which involves performing a hard 5-min blowout effort right before the 20-minute test effort.

92.5% +/- 3% is a typical range for FTP if you refer to mean maximal 20-minute power.

See sin of sins #6:
http://alex-cycle.blogspot.com.au/2009/ ... ftp-2.html
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Re: Calculating FTP without a powermeter.

Postby cyclotaur » Fri May 31, 2013 6:31 pm

Alex Simmons/RST wrote:
cyclotaur wrote:I don't have a power meter or HRM, but I do use a Garmin and upload to Strava. I read somewhere (maybe here) that a good estimate of FTP is to find an effort over 20mins and reduce it by 5%.

Most people's FTP will be less than 95% of their mean maximal 20-minute power. 95% is quoted as a reference starting point .....

Great !! That means I'm not such a slacker after all then. :D
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Re: Calculating FTP without a powermeter.

Postby toolonglegs » Fri May 31, 2013 6:45 pm

If your are taking 95% of your strava power then you probably still haven't got a clue what your ftp is :mrgreen:
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Re: Calculating FTP without a powermeter.

Postby cyclotaur » Fri May 31, 2013 7:04 pm

toolonglegs wrote:If your are taking 95% of your strava power then you probably still haven't got a clue what your ftp is :mrgreen:

True enough - and I really couldn't care less .... :lol:
But it might be somewhere to start for someone who does. :wink:
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Re: Calculating FTP without a powermeter.

Postby singlespeedscott » Fri May 31, 2013 7:16 pm

Alex Simmons/RST wrote:
Arlberg wrote:Is there a way to test for FTP without using a powermeter?

That depends on the level of precision you are after.

With a couple of steep climbs, and maximal performance tests of around 5-minutes and 20-minutes, and with the total mass of you and your bike and kit known, then it's possible to make reasonable estimate…which is what a steep hillclimb does, as the force required to overcome gravity dominates the power demand and is nearly linear with speed, and is linear with mass, two factors that are relatively easy/cheap to measure).

So what is the minimum grade of hill I should be looking for?
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Re: Calculating FTP without a powermeter.

Postby toolonglegs » Fri May 31, 2013 7:27 pm

cyclotaur wrote:
toolonglegs wrote:If your are taking 95% of your strava power then you probably still haven't got a clue what your ftp is :mrgreen:

True enough - and I really couldn't care less .... :lol:
But it might be somewhere to start for someone who does. :wink:

I have plenty of climbs 20 minutes or longer on strava... they are all over the place powerwise on Strava even if I climbed them at similar power.
Better just to climb a steepish longish hill, time yourself and weigh yourself and bike... the plug the details in, its pretty close if your measurements are good.
If you haven't got a hill long enough or steep enough close by... you in trouble :mrgreen: .

If you are going to go to the trouble ( and suffering ) of testing... then you might as well get the most accurate repeatable results you can.

Me I don't bother... I just go and climb a steep hill and compare my times on strava... I know my power to weight sux :lol: .
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Re: Calculating FTP without a powermeter.

Postby Alex Simmons/RST » Fri May 31, 2013 9:18 pm

singlespeedscott wrote:
Alex Simmons/RST wrote:
Arlberg wrote:Is there a way to test for FTP without using a powermeter?

That depends on the level of precision you are after.

With a couple of steep climbs, and maximal performance tests of around 5-minutes and 20-minutes, and with the total mass of you and your bike and kit known, then it's possible to make reasonable estimate…which is what a steep hillclimb does, as the force required to overcome gravity dominates the power demand and is nearly linear with speed, and is linear with mass, two factors that are relatively easy/cheap to measure).

So what is the minimum grade of hill I should be looking for?

Here's something I wrote five years ago:
http://www.bikeradar.com/fitness/articl ... ing-19175/
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Re: Calculating FTP without a powermeter.

Postby singlespeedscott » Fri May 31, 2013 9:26 pm

Alex Simmons/RST wrote:Here's something I wrote five years ago:
http://www.bikeradar.com/fitness/articl ... ing-19175/

Thanks for that. I've got a couple of hills within an hour of riding to try that on.
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