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Power Output - is this the next must-have for cyclists?(24 posts)

Power Output - is this the next must-have for cyclists?Fez
Aug 20, 2002 5:43 AM
I see plenty of questions about what gears the pros use in the mountains. But that info probably not applicable to us, since a pro cyclist should have power output that far exceeds any or us. They can spin gears up mountains at 100 rpm that most of us cannot because we don't have the power.

So besides cycle computers and HRMs, shouldn't a power output device be the next device that cyclists use to chart progress?

If so, how would the device do it? With a crank sensor? I think the Polar unit measures it at the chain, if I am not mistaken.
Not for me, I dont need to see how little I put out. (nm)onespeed
Aug 20, 2002 5:56 AM
re: Power Output - is this the next must-have for cyclists?cyclejim
Aug 20, 2002 5:57 AM
The powertap is a replacement hub, which is probably more accurate that a chain sensor. It is available currently.
nice to know, but...DougSloan
Aug 20, 2002 6:59 AM
What would you do with the information? Isn't speed pretty much the same thing, given similar circumstances?

I'm getting Computrainer rigged up right now, which shows power, but then on a trainer you need something to measure your effort since you are not going anywhere.

I'm as much of gizmo addict as anyone, but I just wonder what people do with watt numbers. When my speedo tells me I'm going 18 mph instead of 20, I think it's safe to assume that my power is down.

If you have a coach who can use the information in programming workouts, that might be useful. It also might be useful to compare two teammates during a race to see if one was better at conserving energy than the other. All this sort of requires an expert to make use of the data, though.

thought it would be most helpful for climbingFez
Aug 20, 2002 7:32 AM
when i train climbing steep hills, i am usu trying to maintain a smooth fast cadence and speed is somewhat irrelevant, because it is secondary to maintaining a smooth cadence (and to save my legs). i think seeing power output progress over time may be helpful.
Aug 20, 2002 8:09 AM
Then what you really want is to see your cadence.

Power, by definition is the rate at which work is done over time. It is a calculated value from other directly measured values and is mostly used as an index for comparison in a labratory or dynomometer (i.e. one race car engine vs. another). There aren't too many race cars that have any sort of on board power indication and these guys run with virtually unlimited budgets. The ultimate question as raised by Doug Sloan (and myself previously) is just what _exactly_ are you going to do with this information that you can't already do with what you have? Thousands of world class athletes before you have fine tuned their performance using the heart rate monitor. Why is this might you ask? Because it directly measures your heart, a tachometer if you will, and gives you a direct indication at just how well your engine/pump is working. Your only basis is that you "think seeing power output progress over time may be helpful", one must assume this is for cocktail parties.
Highly Recommended.........CARBON110
Aug 20, 2002 8:29 AM
I just got an SRM power meter recently. I bought this over a power tap since EVERYONE I know has had so many issus with the power tap. The SRM is incredible and has helped my training alot. I can climb in different gears at different cadences, or sprint, or do the local crits in 12-23 or a 12-25 or hold one gear for 5 or 10 minutes nd another for 5or 10 minutes. I can see how my power changes when I stan to when I sit. Its great. It has made me a more efficient cyclist to say the least. Plus its greatt come home after my ride and download all my stuff. I can d more on my SRM than I ever thought. This winter and spring it will certainly pay off even more. I will go out and preride my PEAK race courses and see how long I can hold specific cadence/power and how long I can do hill attacks witout buring myself out. Its become instrumental to my training.
HR can be deceiving...James OCLV
Aug 20, 2002 8:48 AM
I have this problem all of the time. I'll go out to do intervals, and I have to bust my ass just to get my HR over 145! Does this mean that I need more rest? Should I keep pushing or quit the workout? Is a low HR bad - maybe, maybe not. It could also mean that fitness is high and to keep going - not that you should stop.

On the other hand, if it's easy to get your HR up, you might conclude that your body is rested and you are ready for a hard effort. For unfit individuals, it's very easy to elevate your HR. High HR does not mean that you're in shape.

Where to go from here...

To get the most accurate picture, you should combine power w/HR. For example, if you're doing threshold intervals and you can't get your HR to rise, having a power meter can tell you if you should keep pushing or go home. If your HR is low but power is high, you should continue with the interval. If, on the other hand, HR is low and Power is low, you probably need more rest.
Just another tool in the arsenal...Fez
Aug 20, 2002 12:57 PM
Heart rate, cadence, speed, etc. are all invaluable pieces of info. But I also think Power measurement is another important component because optimal cadence is affected by choice of gears and riding style. Speed is affected by aerodynamics, terrain, choice of bike, etc. Athletes' heart rates differ, and even once you know your own heart rate well, it still is affected by day to day health and recovery (or lack thereof).

I think power measurement is not affected by a lot of other outside factors. I thought having this information would be helpful for training, rather than your assumption that it was for cocktail parties.

If power is relatively unimportant, then why is it frequently tested among elite level athletes?
The reason race cars don't measure power output...James OCLV
Aug 20, 2002 2:23 PM
is because they are machines, and they don't get tired (not entirely true, but that's a discussion for another forum).

To use your race car analogy, Engineers know the exact power output for a motor at any given RPM - it's tested on a dyno before installed - and for the most part if the engine is in good working order that power curve remains consistent. In addition, a vehicle's tachometer isn't affected by wind and temperature. For the post part, power output at 3000 rpm is power output at 3000 rpm...

Unfortunately for the cyclist, the human body doesn't operate that way. Your power curve relative to your "tachometer" is not consistent from day to day, and can be affected by such things as fatigue, wind, temperature, etc..

Based on this idea, an effective way to measure fitness is to compare your power curve (measured w/a meter) to your "tachometer" (measured w/a HR monitor).

I've had many a workout where my "tach" is telling me that I'm tired (or really fit - that's right, as I get fitter, I should have to ride harder and harder to damn, why can't my HR alone tell me what's actually going on in my body...), but my power feels good and my RPE is low. If I just listen to HR, by all accounts I should pack it in for the day and go home!
There are too many variables with speed alone...James OCLV
Aug 20, 2002 8:41 AM
Wind, temperature, grade etc. play too much a factor when it comes to speed to get anything meaningful out of it.

The same can be said about these same variables when it comes to using HR as a guage of fitness, too. HR is a little better because it moniters how your body is reacting to the work load placed on it.

Power is not affected by these variables, and it doesn't "lag behind" like HR. It is better than HR for intervals above your LT. Power alone isn't enough to gauge improvements in fitness, though...

To get the most accurate picture, you should combine power w/HR. For example, if you're doing threshold intervals and you can't get your HR to rise, having a power meter can tell you if you should keep pushing or go home. If your HR is low but power is high, you should continue with the interval. If, on the other hand, HR is low and Power is low, you probably need more rest.

All of these devices are just tools, and none of them alone paint a completely accurate picture...

That being said, NOTHING is as valuable to a cyclist than becoming adept at reading your body. RPE is a highly underated tool, and probable the most valuable.
Yeah ... in the comparison that counts ...Humma Hah
Aug 20, 2002 2:06 PM
Lance Armstrong won the TDF by 7 minutes out of 3 weeks. His power output is impressive, but so is the power output of everyone else who finished on the same day! They're all so close, no power-measuring device could be calibrated well enough to tell a rider using it if he would win the TDF.

However, it would tell me clearly why I won't, probably by a factor of about 3 on power output. And it would tell me if I were making any progress, and prompt me to keep generating higher power numbers, beating old PR's. If the devices have any value, that's it.
the real usefulnessDougSloan
Aug 20, 2002 2:50 PM
The real usefulness might be not so much to see how great the power output it, but how low you can keep it. Some races are a lot about how *little* power you can make, until you really need it -- conservation.

If I had one, I'd use it in a race to keep my power low as possible. That would be useful.

Probably exactly Armstrong's strategy.Humma Hah
Aug 20, 2002 2:56 PM
Hang back in the peloton until late in the race, letting its wind practically suck you along, then go out and reel in the dumb suckers who lit out on their own to challenge the wind 2 miles from the start. Unleash just enough of your awesome power to make the day's leader push to the point of agony to hold the lead, while maintaining your lead, or slightly improving, on the #2 rider.

He did it day after day with remarkable precision.

For me, regulating power output is the only way I can possibly climb big hills. I do it by watching the speedometer. If I don't I'll accelerate to a pace I can't maintain, go anaerobic, and never be able to recover properly.
Here's the torque transducer source ...Humma Hah
Aug 20, 2002 2:01 PM

Coupled with a cadence counter to give RPM, this would give power.

I work for a company that makes a computer/sensor package for Unmanned Air Vehicles. Our newest model is light and compact enough to make a dandy cyclocomputer, if anyone could afford it. It could measure airspeed, altitude, crosswind, angle of climb, acceleration, cadence, roadspeed, and could couple to the torque transducer above. It would not only measure power, but tell where it was going (to air resistance or climb).
Hey Hummayeah right
Aug 20, 2002 2:31 PM
Just curious if you could give me a hint where you work. I've done quite a bit of work with an solar-powered UAV, for an aero class at school and we're using a package from MLB ( for guidence and control. It's pretty fun stuff.
Aurora Flight Sciences/Athena Technologies ...Humma Hah
Aug 20, 2002 2:47 PM
... look us up at

Pres.: John Langford (headed the Daedelus 88 human-powered flight epic that recreated the original Daedelus flight.

Stored in a trailer in the back of the hangar, we have the Michelob Light Eagle human-powered aircraft. There are periodic threats to get it out and get it flying again. I'm ready when they are. There are a dozen cyclists working here.

The new product I've got my eye on is GuideStar GS111m, the lightweight economy version of the original model. Still way to pricy for anyone but top pros, though. I think I've seen the spyplanes gizmo -- clever and fairly cheap and small. Ours will out-perform it, but ain't cheap and is still not as small as we want for micro-air-vehicles. We've got airspeed, altitude, alpha, beta, 3-axis magnetometer (which gives you attitude), 3-axis accels, 3-axis rates, GPS, and a bitchin' little computer running a Kalman filter to cross-check all the sensors. The computer has a number of PID outputs to drive servos directly, plus various serial busses to communicate with such things as serial servo packages. We have Dave Vos doing the flight control equations (this is the guy who built the unicycle that could drive itself, completely autonomously). The GS111 has recently flown the OAV, LAM (see a recent Aviation Week), and Mars HADD aircraft.
Aurora Flight Sciences/Athena Technologies ...yeah right
Aug 20, 2002 3:09 PM
you guys do good work. i think our whole budget for our uav project was like $30,000, so your gear would be a little out of range, although it'd sure be nice. the mlb board is only 8oz. and that's a big factor, although the darn pressure sensor saturate at 10,000 feet, which is about 1/5 of where we were hoping to go. daedalus is sweet, my advisor was at MIT for that, and he was telling me how they were so weight conscious that they were using syringes to measure epoxy. heck i'd break the wings off trying to generate enough lift before i could take of in the thing. anyway, that's really cool. i don't know if you have any connection to the mars plane, but that's a fun project too, my school has been working on that recently, sure is a hard engineering problem though.
Aurora Flight Sciences/Athena Technologies ...Humma Hah
Aug 20, 2002 7:05 PM
We've worked on various versions of the Mars plane for some years, basically trying to come up with a folding wing design that can deploy in-flight from a heat shield. We're in competition for a NASA contract that is hoping to launch in something like 2008.

Our altitude sensors can be set for whatever you want. I calibrated one to 100,000 ft recently, high enough to give an SR-71 nosebleed. The GS-111m might just about fit your weight requirements and will be much cheaper than the original GS111, with the same capabilities and some improvements. I've not seen a price on it yet. But we have cockeyed plans to get one down to about matchbox size and under $1k for micro air vehicles. Not real soon, though.

But, to get this back to a cycling topic, the crew there is unusually physically fit. Two serious MTBers, one VP who would LIKE to be, one legend in the theory of why bicycles are stable, several others who's cars have bike racks but never bring 'em to work, and about four of us who commute, at least on occasion, by bike. And since we're airplane nuts, the idea of getting Light Eagle back in the air is pretty interesting.
interesting ideaDougSloan
Aug 20, 2002 2:32 PM
With a 3d global positioning device, programmed-in mass of bike and rider, and wind speed, couldn't a computer calculate power?

You could come pretty close ...Humma Hah
Aug 20, 2002 2:51 PM
With the analytic cycling website's equations, if you knew the aero drag of the rider, you could make a pretty good stab at power. And if you did a few coasting tests down grades (which the instruments could figure for you), the drag could be worked out by the computer.

The catch would be keeping the drag constant. Changes of position from the position used for calibration would make big changes in actual drag.
think soyeah right
Aug 20, 2002 2:51 PM
you'd just need a very accurite drag model for the rider, under all cross winds and such, could be hard, and gps sensors, don't tend to be super refined, so small differences in speed could make a significant impact in power.
for racers, yesDuane Gran
Aug 20, 2002 4:13 PM
For competitive use, I swear by a power meter. I'm able to look at the data from races and see quantify my strengths and weaknesses. As a piss-poor sprinter I can see that 800-900 watts isn't cutting it. In training I can use this figure as a goal and measure real progress. It doesn't matter if I practice sprints uphill or downhill because the wattage doesn't lie.

Others have made plety of good points about how wattage is preferable to speed, but I'll just say that it adds a dimension to training.
if this is about gearing, I know the answercyclopathic
Aug 21, 2002 3:34 AM
Your question isn't only about power, climbing performance defined by weight/power ratio and pros besides being capable of putting high output also have lower body mass.

TdF contenders can climb at 100-120' per min; I don't think there's any in pro peloton who climbs under 90'. Cat 4 avg is ~60', so let's say your gearing should be ~1.5+ times lower to make it comparable. Triples with 12-27 cass will have 1.53 lower gear then doubles with 12-23, used by GC.