Power Output in watts

Chris65

Articles on training often refer to the riders output in watts.

Is this measured by some device or can it be calculated?

cougie

Measured by powermeters and some turbos.

StageWinner

Generally expensive devices.


Powertap wheels = £500 and up
Quarq (Crank based) £1000 and up
SRM (£2000ish and up).

And some turbo trainers (but good ones that are expensive).

Probably the best tool for training though (some form of power measurement). Make it easy to train smart, stay in the right 'zone' and measure changes and improvements.

a_n_t

Best thing I ever bought was my powertap.

Herbsman

If you hook your turbo up to a grid of 20W light bulbs you can easily measure your wattage but you must take into account energy losses in the form of heat and vibration due to friction and to electrical resistance

lef

Herbsman wrote:

If you hook your turbo up to a grid of 20W light bulbs you can easily measure your wattage but you must take into account energy losses in the form of heat and vibration due to friction and to electrical resistance

...why just have it on a turbo, if you put it on a trolley you could tow it down the street.

Jcrossland

A lot of leisure centres are getting wattbikes. Very similar to an indoor cycle but a closer experience to road biking. These will measure your wattage. They also allow you to analyse your technique in that they show your power curve and leg use ration.

cougie

Bit wasted in leisure centres ? They're very decent kit.

StageWinner

Jcrossland wrote:

A lot of leisure centres are getting wattbikes. Very similar to an indoor cycle but a closer experience to road biking. These will measure your wattage. They also allow you to analyse your technique in that they show your power curve and leg use ration.

Your council must be well flush if they can afford Watt bikes in their Leisure Centres. Those things are freaking expensive! :shock:

DaveMoss

i can see the value of power measurement for full time pros' because they can put in the training time to fine tune their performance and make use of the data. for your average amateur, it seems over the top, and probably too much information.

The key to measuring how your training might be going is to have a turbo set up that stays consistent, e.g same tyres, same bike same tyre pressure. Then if you can go faster.farther in a given time, you are producing more power. At the end of the day, it does not matter what your power output is, you only need to know if it is increasing or not.

SBezza

Powermeters can help any rider, and are certainly not just reserved for pro riders. It gives you very reliable data to check progress with, and if used with good software can monitor training load, and help you avoid overtraining.

There are plenty of amateurs that race very successfully at an amatuer level, it might not be required for your general club rider, but there are quite a few riders out there that benefit enormously from having reliable and repeatable data. General turbo's just don't give that no matter how well you set them up. Without a powermeter there is no way of knowing if your power is increasing, changes can be very subtle.

At the end of the day it is just another tool, but a very accurate one at that.

DaveMoss

This is the beginners forum. best advice for a beginner regarding power meters is "forget it".

Pokerface

DaveMoss wrote:

This is the beginners forum. best advice for a beginner regarding power meters is "forget it".

Power meters are how beginners stop being beginners.

kayakerchris

second best thing I bought was my power meter. SRM linked to a Garmin 705. Got it about 2 months ago. Did a sufferfest on the turbo and was absolutely dead at the end. uploaded to training peaks and out pops my functional power, etc. Then I get the endurance power level, tempo, etc. Easy to now sit in the endurance power band for a 3 hour cycle. Dont even look at the speed until I get back to the house.
Chris

a_n_t

DaveMoss wrote:

have a turbo set up that stays consistent.

and now I have a powertap I can see just how difficult that was.

SBezza

DaveMoss wrote:

This is the beginners forum. best advice for a beginner regarding power meters is "forget it".

The OP was asking about them, and what there were, most of the answers on here are saying what they are. Only you have rubbished them.

A PM can help a beginner and an experienced rider alike, there is no pre requirement for owning a PM. If you can't afford one you don't buy one, but if you are serious about getting better and can afford one, then why not.

1_reaper

I find my Tacx Fortius good at showing me all the data including watts. As has been said before as long as it is calibrated right and the same tire pressures etc. gives a good indication of how I'm going. Not the cheapest bit of kit but worth while getting for when you can't get out because of the weather. Roll on March for the Garmin vector pedals so i can see what's going on after a ride on the road

Monty Dog

Another aspect of consumer pressure on racing - it used to be that your 'couldn't race' without a decent pair of carbon wheels, and now it appears you're not serious about your training unless you've got a power meter? What utter bollox - you become a stronger / better riding by the strength of your heart, lungs and legs and not what's strapped to your bike. OK, a power meter may help you develop a structured training programme, but you have to do the miles and make the effort rather than simply unload your wallet.

BeaconRuth

Pokerface wrote:

Power meters are how beginners stop being beginners.

With respect Pokerface, that's a very silly statement! If I was a beginner cyclist and I went and bought a powermeter would I stop being a beginner?

Ruth

briantrumpet

Beginner, obviously. He probably never took his stabilisers off.

Alex_Simmons/RST

DaveMoss wrote:

i can see the value of power measurement for full time pros' because they can put in the training time to fine tune their performance and make use of the data. for your average amateur, it seems over the top, and probably too much information.

The key to measuring how your training might be going is to have a turbo set up that stays consistent, e.g same tyres, same bike same tyre pressure. Then if you can go faster.farther in a given time, you are producing more power. At the end of the day, it does not matter what your power output is, you only need to know if it is increasing or not.

The power meter is a tool, not a bolt on motor. One needs to train in order to get fitter, and no-one is suggesting that having a power meter is necessary to train hard.

But it does provide a range of benefits, which may or may not be of interest to riders of all levels.

I made a summary of those benefits here:
http://www.turbostudio.com.au/canberra_camp_power.html

Used intelligently, a power meter can definitely help one improve performance, but it doesn't pedal the bike for you.

Alex_Simmons/RST

Chris65 wrote:

Articles on training often refer to the riders output in watts.

Is this measured by some device or can it be calculated?

Both.

There are devices you can fit to bicycles, called power meters, that actually do measure the power output of a rider. There are also indoor bike trainers that measure power.

Various devices exists that measure the forces and speeds applied to the rear tyre, the rear wheel hub, the cog, the chain, the crank, the bottom bracket, and the pedals. There are some purported to measure forces in the shoes. Those forces, along with information about the velocity over which those forces are applied allow these units to calculate power.

Not all such devices are readily available for purchase but there are a few very well know brands and perhaps 200,000+ power meters in use today (if you include power measurement trainers).

Some are more reliable and accurate than others.

Measurement of power output on a bicycle is not a new thing. The first power measurement ergo bikes were made over 100 years ago.

And due to Newton's law of motion, you can also calculate/estimate power output provided you have enough information about the various resistance forces working against you. These include air resistance, rolling resistance, gravity, drive train and bearing friction, and inertial load.

It is however really difficult to accurately measure all of the factors that provide all of the resistance forces. Some can be measured readily, others require assumptions be made. Some devices estimate power via this method.

There are situations where quick estimates of power output can be made with reasonable accuracy, e.g. within 10%, when a rider is climbing up a steep climb, and all you know is the gradient, the weight of themselves and their bike and gear and how fast they are going. That's because one resistance force (gravity) becomes dominant over all others and so the impact of getting some of the assumptions/measurements wrong is minimised.