Power is Knowledge

In my opinion in the next three to five years power measuring devices will be as prevalent as Heart Rate Monitors are today.  In other words, everyone will have them.  In this article I'll try to explain why power is important, what the options are, and why you could benefit from training with power.

I've been using power as a measurement factor in my training for about six years now.  And I'm just about getting the hang of it!  I bought my first heart rate monitor in 1986 and I've still got it!  Me and Guy Webb had one.  He was winning everything so I thought I'd get one to help me on the road to success.  What I didn't factor in was the abundance of talent he had.  Still, mine helped me to understand how my body worked.  More of which later.

Power vs Heart Rate
Heart rate is good, because if you didn't have a heart rate you'd be in serious trouble.  But what actually is a heart beat?  What does it represent?  Is one of yours equal to one of mine?  I doubt it.  A heart beat is relevant to you and you alone. 

If having the fastest heart rate was an indicator of speed and endurance by which you could win races, it wouldn't be worth any of you turning up.  I can guarantee I'd win every race I'd enter.  At the age of 46 my max is still around 232 bpm. 

From the very first heart rate monitor I've had, which everyone was telling me was useless because it read so high, my readings have always been the same.  Resting 48, max anywhere over 230.  Click here to see my heart performing in a local crit.

So this 220 minus your age malarkey is a total waste of time.  I get so annoyed when I see magazine articles and even coaching manuals offering it as an option.  How can you base a personalised training programme on a generic, highly inadequate, supposed formula?  If you haven't done a max heart rate test you're building your training on a false premise and the quality of your end results will match those of your initial inputs.

What is a watt?
Did you see what I did there?  A watt is basically the calculation of work done divided by time.  Very hypothetically; If you ride up a hill at 10 mph and it takes you five minutes to reach the top you could expend say 500 joules of energy. 

If you go back to the bottom and ride the same hill at 15 mph it would take you three minutes to get to the top.  But you've still done the same amount of work only over a shorter timescale.  So you still end up expending 500 joules of energy.  You already know a watt is a ratio of work against time so we can see you must have produced more wattage on your second run.  It doesn't matter a toss what your heart rate was!

We can get in to all sorts of psycho-babble about work being in Newton metres or joules, angular velocity, torque radians, inertia, drag co-efficients, frictional losses etc, but not now. All we need to know is that when we stamp on the pedals, they go round, we go forward and we generate power.  Power we can measure and power we can compare directly with others, or more importantly, ourselves. 

You can see who generates the most power during the sprint at the end of a race.  It's not always the winner!  So how much power do you need to win a sprint?  I know, I'll tell you later.   

Who are the players?
At the moment there are realistically four players in the market offering various systems to measure power.  They all approach the issue of power measurement from a different angle. Each has their advantages and disadvantages, I'll try to be as objective as I can and give you the information to draw your own conclusions.  So here goes.

SRM
Uli Shcroberer was one of the first to produce a commercial, mobile power measuring device.  This is the ones the pros use and the one I have.  It fits direct to your existing bottom bracket, replaces your original chainset and requires the fitting of a wiring loom exactly the same as you would with any bike computer.

It's the most accurate of all the devices and measures power at the point of origin, your feet!  At a cost of around £2,100 it ain't cheap.  But it is the best and has proved 100% reliable,  Power is measured where it is generated so there are no frictional losses and you get an exact indication of your power output.

The fitting of the system takes about forty five minutes and requires, obviously, the changing of the cranks.  There is nothing else to do except calibrate the system before each ride.  You press two buttons, pedal backwards, let the system adjust to the ambient temperature, and five seconds later you're off. 

By fitting a wiring loom to your training bike a quick ten minute change of cranks and you have a winter training system.  The measuring unit is fully sealed and weather proof.  There are no other concerns, other than the price.

Power Tap
The Power Tap, used by Floyd Landis, measures power at the rear wheel hub.  This obviously requires a wheel to be built around it, which is a specialist job.  The Power Tap reads slightly lower than an SRM because the power is measured at the wheel. You get torque deflection and frictional losses etc through the drivetrain giving a reading around 98% of power generated at the chainset. 

The fitting of the system, wiring loom and computer unit, once you have the wheel, is around the same as the SRM. 

You need to seriously consider which wheel you fit a Power Tap system to.  It can't yet be fitted to a disc wheel so you'll need to have an aero wheel for your TT bike.  If you fit it to your best race wheel then you'll be fretting all through the winter.  However for the mid-market price of around £600 you can afford to have a winter wheel built up, then strip it and build a race rim on it for the summer.  A small wheel-building price to pay for versatility.  And by the same token, if you fit a loom to any of your other bikes, a quick 30 second wheel swap gets you all powered up.

Ergomo
The Ergomo system is a clever opto-electronic system that replaces your bottom bracket. It determines the current power output of the cyclist by measuring the twisting deflection (the torque) in the bottom bracket axle and converting the reading in to watts. The system is sensitive enough to detect a minimal distortion of only 0.0025 degrees.

This is how the SRM and Power Tap work, they just measure the deflection at different points of the drive train, the pedal and hub respectively.  Again you need to fit a harness and computer unit to your bike.  if you need to swap between bikes well it's get your tools out and change the bottom bracket.  Around an hour if you do it properly.

One bonus is that the Ergomo comes with the fantastic Cycling Peaks software for free,  You also get to use any wheel you want and your lightweight carbon chainset.  At around a £1000 it's in the mid to high price bracket.

Polar
The Polar system makes full use of your existing (compatible) heart rate monitor so you save a few bob there.  A complete Polar Power Package can be had for around £350. 

This system measures the friction, vibration and speed of the chain to generate a power algorithm.  It isn't a true power output but it does give a reasonable indication.  Obviously the chain has to be in top condition.

However, the fitting of the system can hardly be called straightforward.  You need to dismantle the rear mech, remove and weigh the chain, fit a chain frequency sensor, fit a chain speed sensor, fit a cadence sensor and a wheel speed sensor and the wiring loom includes the measuring system.  Also, the chain needs to be just the right length to prevent over reading in extreme chain lines.  Which means that when you change your cassette you may get dodgy readings. 

To be honest changing between bikes is as good as out of the question!

The Good the Bad & The Ugly
The SRM is the easiest to fit and least intrusive system but the pro system comes at an extremely high price and is twice the cost of it's nearest competitor.  It's accurate, easy to use and looks the business.  It has a low aggro-swapability quotient, a high pose factor and is probably the second best value for money.

The Power Tap is slightly more difficult to fit, as it requires a new wheel to be built, but once you have the wheel you're laughing. In the mid-price range, it has a a high spec, a middling agggro-swapability quotient and a middling pose factor.  In my opinion this is by far the best value for money overall package.

The Ergomo system is a real neat system.  Too neat.  If it wasn't for the larger than normal handlebar mount no one would know you had a power measuring device fitted.  It has a mid to high price factor, a high aggro-swapability quotient and a low pose factor.  I'd probably place it between the Power Tap and the SRM.

The Polar system fills a basic need, it's the cheapest, the lightest and more prone to inaccuracies.  It most definitely fits into the ugly category but is better than not measuring power at all.  It has an off the scale aggro-swapability score, is high maintenance and has a low pose factor.  Having said that it does measure power and it will give you results.  Although all the other systems can measure per second, the Polar will only measure averages over five second intervals.  Don't discount it.

Why Power?
When you start an interval or training session you generate power and a physiological response from your heart.  If I ask you to crank out 300 watts for 10 minutes, you can see from the green line on the left that from second one we had 300 watts. 

However the heart rate lagged behind and took a while to stabilise.  It started at 165bpm and levelled at 175bpm.  The lag is around 8%.  So if you do your training intervals by heart rate you can expect to be 8% down on the equivalent interval carried out by power.  Or to put it another way training with power is around 8% more efficient than training by heart rate alone.

To win a sprint in a vets race in Jersey you need to sustain over 700 watts for over 20 seconds.  I know, because I've won one and have the print outs and figures to prove it.  If you train by heart rate, or just do sprint intervals on the road, how do you know you're knocking out 700 watts.  The first time you'll find out is when you enter the finishing straight.

As I said earlier, the person with the highest heart rate will not win the race.  The person with the highest power output will not necessarily win, but the one with a combination of the highest power to weight ratio and greater tactical awareness probably will.  Measuring power during your training sessions lets you know exactly where you are in the scheme of things.  You either can or can't generate 700 watts for 20 seconds.  It's as simple as that.

The Message
Power measurement is the future.  But it's not a replacement for heart rate monitoring.  Using the two to complement each other gives exponential factors of benefit.  What I mean to clumsily say is; "Even though a Heart Rate Monitor and a Power Meter represents 50 % each of the overall measuring equation, when you combine the information of the two you get more than twice the benefit".

Unfortunately not everyone understands how to get the best from their heart rate monitor.  I can see that from the amount of people I test that are "unsure" of their maximum heart rate.  They all have a heart monitor but have no idea of their lactate training zone, VO2max training zones or even the normal WCPP training zones.

So just fitting a power meter will not make you a faster rider.  Fitting a power meter will give you the extra dimension to your training that will help you realize your potential.  And that's what this site is all about.  helping others realize their potential.

Before you splash out on a new set of wheels ask yourself this question; "Will they make me a better rider?"  The answer is definitely no.  Now if you were to ask the same question about a power meter, the answer would definitely be yes, if you used it correctly.