Athletics and Recreation

Are Power Meters Useful For Mountain Biking?

Are Power Meters Useful For Mountain Biking?

– You would be hard pressed to find a high-performance road cyclist that doesn’t have an intimate knowledge of power meters and watts. But for one reason or another they’re not so prevalent
with us, mountain bikers. But why? So what is a power meter? What does it do? And what can we learn from its readings? So I thought I’d ask the
man himself, Mr. Chris Opie, who not only was a
professional road cyclist for most of his life, but is also damn handy on a mountain bike. So hopefully, he was able to
shed some light on the issue. (air swooshing) (metallic blades swishing) So Chris, what is a power meter? – So a power meter is
a device on your bike either in your cranks or your spider. It can be on your bottom bracket, it could be on your pedals, or it could be in your rear hub, although you see those less these days. And it’s a device that measures
your power output in watts. – Okay cool, so how does it measure power? – Okay, so generally speaking, the more expensive a power meter, the more strain gauges it has inside of it and the more accurate they are. And a strain gauge is a very lightweight, thin piece of foil, and it’s put onto a piece
of metal, it’s glued on, and there’ll be an electrical
current flowing through it, and that will measure the
deflection of the material that it’s stuck to, which then calculates your torque output, which then multiplied by
revolutions per minute gives you your power output in watts. – And what is a watt? – So a watt is an expression
of a measurement of workload. So I think a watt roughly translates to the workload of a dual pump per second. – Wow. So what affects us then? If I’m in a big gear pedalling away, putting a lot of torque
through the cranks, do things like rpm and the gear I choose affect the wattage reading? – Yeah, definitely. So you could be riding
along in a really big gear, imagine you’re on the flat and
you’re doing 20 Ks and hour, or 12 miles and hour
along the gravel path, and your in top gear. So in the 11 or the 10 at the back. And you’re peddling at around
60, 55, 60 revs per minute? – Right okay.
– You’re going to be producing a lot of torque to continue the momentum. So it’ll be like lifting a
really heavy weight in the gym. Whereas if you’re in
the middle of the block you could be spinning along at 110, 120, producing a lot less torque, but your wattage reading is
going to be very similar. – And so, are they linked? Is rpm an important measurement, or your revolutions at the cranks, is that an important measurement
for getting our wattage? – Yeah absolutely, so higher your rpm, the more of your cardiovascular
system you’re going to be using to produce the power. But you won’t need as
much torque to do that. So people will argue that
it’s actually less fatiguing on your legs. Although realistically,
that sort of fatigue is kind of it’s self-inbuilt, everyone has their preferred cadence. Some people prefer to pedal
at 70 rpm for example, and some people prefer to
pedal at a little bit faster. – So if you were putting a
power meter on a mountain bike what would be your preferred setup? Do you think you’d go the
same like you do on the road in the crank set? – Yeah, definitely in the crank set, not in the pedals, not in the hub. I think I’d probably stick with the spider or in the crank arms. The crank arms is quite good because they’re not
going to take any impacts onto the chain ring are they? So the only impacts they’re getting are just standard crank arm impacts that you’re going to have anyway. So maybe that’s actually
probably the safest for a mountain bike.
– For a mountain bike. Now there’s a key word I think when we talk about power meters, and that is consistency. Because I’m not that experienced of training with power meters. I’ve done a bit, and I’ve actually got one on my bike currently. But I suppose that the number to a degree isn’t that important as long as you’re always
training to the same number, if you’re to do any structured training. And the number’s constantly changing. It might be flattering you some days, it might be deceiving you on others. – [Chris] Yeah, that’ll be the worst. – But that’ll be the worst actually if you’re
wattage looks a bit lower than you think it should be. It might not be the end of the world, because if you can still get a structured training session in, to maximize the effects of
your high load training, well surely that… Is consistency king?
– I think so. Accuracy is really important but it’s less important
than it was years ago. So years ago, when power meters were new, you’d have all sorts of issues. They would drift with temperature. So if it got warmer while
you were out on your ride you’d find that your
power’s just ramping up and you could hold numbers
that normally you wouldn’t of, which is really, is amazing. I had one season where I went through seven different power
meters, all the same brand, and it was purely because of that, purely because of the drift. And you get to the end
of a really hard effort and you’ll still be doing
almost peak numbers. You’re, “I’m not sure this is right.” But I feel it’s a real
good confidence boost. – Yes. Now I’m pretty old school I’d suppose in that I’ve trained
with a heart rate monitor for a long time. Is heart rate monitor better
or worse than power…? Or is it just different? – It’s different, but at the same time, I wouldn’t disclude one or the other. I think a lot of riders get so focused on power is everything. For years, I didn’t even
ride with a heart rate strap. Whereas now I would, just to
get that extra reference point that I mentioned before. It’s better to have a
more complete picture, and the more information you can get, if you’re training to a serious standard the better obviously. But I don’t know that one is
necessarily going to be better than the other. It’s partly what you get
used to, what you can afford, ’cause power meters are
not the cheapest thing out there are they?
– No, it’s very true. – Luckily these days though, you can get good software that estimates your power output as well. So there are certain
online ride logging sites that will give you an
estimate for your entire ride and actually it’s not
that far off anymore. – So, I’ve been doing a bit
of the old Zwift recently. And my bike doesn’t have
a power meter on it. But I’m getting a power reading. How does that work? – So Zwift has got loads
of algorithms haven’t they with stored turbo trainers numbers. So they know that if your
rear wheel is spinning at a certain speed, roughly what that equates to
on whichever given circuit based on your weight. – So I guess it opens up using
power as a training tool, even if you don’t have any of
the power meter componentry upon your bike. – Yeah, makes it much more affordable, and you can just jump on
with a speed sensor and go. – And go.
– Pretty good. – Which is pretty good, yeah. So, we’re seeing it more and more with high-end in WS races,
and some downhill races. And they have a power meter
on their downhill bike or their Enduro bike. Now this bike is mainly
there for descending. What’s power got to do with it? – Well it’s going to help
analyze the event isn’t it? So it will help them then
go back with the coaches work towards a training program. So create the best athlete possible. So out of the start gate, how
many watts are they producing? Are they still able to produce anywhere near that power further down? If they’re not, then that’s highlighted in the fact they fatigue quite quickly. Is their heart rate sky high and they’re not able to get the power out on the transitional sections? So EWS, that’s more important. And so actually, for EWS it’s
going to help them save energy between the stages as well, because they’ll know at no point should they be peddling too hard. – [Doddie] That’s very true. – That’s a really important
thing about power meters is they’re really great
for holding you back when you don’t need to be
wasting loads of energy. – That’s true. I suppose with power meters there’s a big number of watts per kilo. So you can predict how fast
you’re going to climb the hill. So that could help give
a better estimation and then so you’re not standing at the top twiddling your thumbs for 20 minutes– – No exactly.
– … Taking it easy. – If you’re really analyzing an event, you know that you’ve got X amount of time to get to the top. Don’t do it in half that
time and then stand around like you just set it. Just cruise up the entire time. It’s going to save a lot more
energy, you’ll recover better. I mean, you’ll be faster on the next run which is more important. – So, a final question then. Are power meters for mountian bikers? – Absolutely, I think
they’re for everyone. Anyone that wants to improve
their cycling in some way will benefit from using a power meter. – Well, there we go then, simple as that. So that is it, I think we’re
a bit better educated now about what the hell a power meter is. – If we’re not, you will be next time. (laughing) – Totally, but I’m going to throw to a cross country versus
mud tires comparison I did a little while back. So click down here for that one. – Ooh, if you want more
technical advice right now, check out Doddie’s Geometry
101 just down there. – Ooh perfect. As always, don’t forget
to Like and subscribe, and we’ll see you next time. Cheers guys.

Reader Comments

  1. What about on and off the saddle because mtb is all standing when descending?? Do power meter still measure some watts when off the saddle and when during G-out?

  2. Great topic, the problem is the lack of mtb specifik power meters on the market. I Suggest a Garmin edge 830 and a heart strap before you go all in on a powermeter. Cheers

  3. Most mtb veidos on youtube are trail, enduro, or dh… Dont see the point for those disciplines… Xc would make sense if youre a pro

  4. Clear as mud 😂 I’ll just keep peddling, sending and recovering… safe in the knowledge I’m getting some exercise but more importantly I’m having fun

  5. Heart rate monitors are more than enough for accurate xc mtb training. Terrain is too inconsistent to accurately gauge power output over extended periods of time.

  6. I’ve been using Zwift with my mountain bike, but I find my gear ratios are too low to work in the flats and downhills in Zwift.

  7. Road/gravel bikers have been borrowing from MTB tech and style for a while now, makes it "more fun".
    Let's not do the reverse and start caring about speed and power – it'll make Mtbing more boring! I'm yawning already. (exception – if you're competing)

  8. MTB riders carry a lot of heavy stuff on them (like back packs) , their bikes have larger tires and lower pressures and these cause more attrition.
    More over they climb steep climbs on accidental terrain which is much more harder that when climbing paved road.

    All these at the end come to a higher need of watts. Now if the rider is also heavy or more muscular and don't look like a skinny road pro rider, then the needs are higher.

    In other words: An MTB rider might be slow, if he is not all downhill maniac, but the watts he produce are generally speaking higher = more fatigue in less K's
    Put it simpler : 40k on an MTB FS is probably equal to 60k on road (considering same diff in altitude).

    Power = work / time.

  9. NO! Just one more tech for tech sake that rapes the consumer. Anything to sell to the already outrageously over hyped and priced bike market. Waiting for the more accurate Sweaty Balls monitor to measure my energy output. Can't wait for the mini windscreens to reduce air resistance.

  10. Measuring g-forces would be a better thing… how hard the berms are railed, how fast down hill, how hard the brakes are applied… visualise that in a 3D model based on altitude, vectors and speed variables and you would have a work of art….

  11. I read the title and was like
    Just why, just started a channel and you guys got me into mountain biking so thanks!

  12. no useful … mtb or btt … it not just power … but techniques to transpass the difficults during XCO or XCM counts more

  13. 🗣️yyyeeeaa Henry and Cris Opie the cualificasions of thes rider's in cad session's in the climate relative and exstremadment cambiant and differents temperatures difern terrens for thes carrers o trails descendins so faster in the sending in ricoding day cronometrad the #mtb o #Downihllbike's and #sincros.

  14. @GMBN Tech… Power meters only make sense to marathon mountain bikers because they are the only who care how many watts it takes to ride a kilometer. The shuttle my ass up the mountain crowd really doesn't care about how effciency because it really isn't a factor on the chair lift.

  15. Just like with heart rate monitors: only a limited amount of people really know how to use the data to create a better result compared to what you could reach without them. There is a reason why some of them are paid that good. If you have the money at hand and want to spend it on a power meter, just do it. If you have other things that are also important to you, remove the power meter of the list quickly.
    Don't forget that power output, just like heart rate is something that changes if you train in a good or bad way. If you notice your power output is increasing while you are still able to sing a song, you know you are improving, you could also notice that in your speed, but speed depends a lot more on the terrain, weather conditions (wind..). That is a big advantage of a good power meter. The heart rate you can reach while still being able to sing will most probably also have been changed. Otherwise said: if you want to use that data during training, you need to have the knowledge how to detect to correct values to use yourself or have someone that knows how to use it and tell you about the changes. Do not trust a device to do so correctly, the average person is the average and is not you (unless you are very lucky).
    It is also important to know that having stress, being ill, not enough sleep etc influence the amount of power in relation to your heart rate you can deliver, so never forget to include the 'data' about how you feel in the total amount of data you have at your disposal.
    A final note: you don't need those things to have fun in the field/forests/..

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