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 as they will be integral to the groupsets you buy off the shelf.
In this article I'll try to explain why power is important,
what the options are, and why you could benefit from training with
I've been using power as a
measurement factor in my turbo training since 2000 and on the road since
2003. 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.
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.
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.
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
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.
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
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
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, 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 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
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 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
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!
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.
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.
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.
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.
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.