What are watts?

Today’s question was asked by Andy Moody who wanted to understand watts & cycling.

Basic theoretical understanding
Watts is the measurement of power derived by Scotsman James Watt. This looks at the rate of energy which can be converted into power over a period of time.

You might find it easier to understand if you think about the light bulbs you have around your house . A 5watt lightbulb will be dull. However a 50watt lightbulb will be bright. More watts in this example means a brighter bulb.

Cycling application
So if you cycle at 80rpm you will generate a certain amount of force, which we can call power – measured in watts. If I put more resistance against the bike I.e hill, wind or harder gear BUT hold 80rpm you will need more power / force to move the mass I.e you & the bike & the resistance.

Therefore you will generate more watts. This in turn can increase the speed. HOWEVER if you are flying down hill at maximum speed your watts will be super low, if you are grinding uphill you speed will be low but power output high

force = mass x acceleration

On the flat you might understand it like this. The quicker you turn over your legs (cadence) with a resistance you will improve the power of your legs. I.e 80rpm = 25kph then 90rpm = 30kph.

How can you use watts in training?
Like a computer game where you have special life’s, you have a certain number of times when you can generate more force. Then more times you use them (burning matches) then you will run out and then have no power. This could be going to hard up a hill, chasing someone down too quicker or going too fast. Knowing your watts is to know how much effort / power you can use before you burn a match. So if you hold a certain watts in training for 30mins you should look to hold that during a race to ensure you use your power equally. If you hit a hill then you should ride up it STILL within that pre-determined watts range to ensure you don’t burn a match & go to hard and then need to back off because you have produced too much lactic acid in your blood.

If I don’t have watts what can I do?
This is slightly harder to control. HR is reactive to stress, tiredness, caffeine & so your HR can be hight without doing much WHEREAS watts are proactive & there more more controllable. So you could use a scale of effort – this is known as the Borg Scale (6-20) but we use 1-10 with 10 being maximal sprint and 1 being sitting down. When you think you are working too hard then you might be generating too much power.

What are my power options?
There are more options these days to train with power. They vary in cost & therefore people’s budget. Here’s a simple guide – prices are a basic guide.

Powertap – your rear hub hold the measuring devise & uses ANT+ (I.e garmin computer) £500
Stages – new left hand crank & uses ant+ £700
Rotor LT. – same concept as stages £700
Garmin vector pedals – devise on both pedals & used ANT+ £1200
Rotpr power cranks – new cranks with devise inside £1500
WattBike – the daddy – Judge Dredds bike basically £1600 – £2000
SRM – new cranks – £2500