Stages PM - anyone had issues with indoor use?

mamba80

no u didn't get what I was saying, a HRM would show a higher hr into the wind at 12mph and a low hr with tail wind @ 25mph, so u dont need a pm to demonstrate this, obviulsly there is more to it than this but I m tired!
I am not saying that a hr is a replacement for a pm either if a pm works for the rider, then great, used correctly, they can be fantastic aids.

Alex_Simmons/RST

meanredspider wrote:

That kinda shows the nonsense of statistics without understanding of the underlying data. Power is proportional to the square of speed (the well understood relationship) but your chart would suggest that speed is directly proportional to power.

Keep in mind that Robert was plotting hillclimbing speed, and the speed-power relationship becomes very nearly linear the steeper the climb.

The power-speed is actually a cubic relationship overall (It's air resistance force and not power that is proportional to the square of speed) but the various resistance force components have different impact on the power v speed relationship:
Relative air speed (cubic)
Changes in kinetic energy, i.e. accelerations (quadratic)
Wheelbearing and drivetrain friction (quadratic and linear)
Rolling resistance (linear)
Changes in potential energy, i.e. working against gravity (linear)

Which components of the resistance forces dominates depends on the terrain and speed, e.g. on flat ground air resistance dominates, and so the cubic part of the power-speed relationship dominates, but when climbing, gravity becomes thine major frenemy and the power-speed equation becomes almost linear.

Since Robert was plotting hill climbs, then it's no surprise to see a very nearly linear plot of power v speed. That's why I have in the past suggested hill climb speed can be a reasonable proxy for power when testing fitness.

Of course wind can have a substantial impact on hillclimb speed-power relationship, exactly as Robert shows with the outlier data point on a windy day.

meanredspider wrote:

One of the real insights that the Stages has given me is the effect of windspeed. On the flat exposed areas of North Holland I can be putting out 300W in one direction and doing only 12mph and only 200W in the other direction and doing 25mph. A stopwatch is pretty useless in those circumstances. Even air temperature makes a noticeable difference to power requirements even in completely still air.

Yep, and you can see now how helpful it is on a variety of terrain. Robert was showing hillclimb speed.

But Robert was also suggesting that in general, guidance of intensity of effort, while really important wrt training, is a relatively low-fi application of a power meter.

frisbee

RChung wrote:

frisbee wrote:

To be fair they are generally within a couple of % of each other, which is bloody good when you compare it to other far more expensive power measurement, for example car dynos.

Yes, but I generally try not to pay too much attention to expense when I do these analyses. That is, I know how much I'm willing to pay but I try not to presume that everyone is like me. So I generally just try to identify the strengths and weaknesses regardless of cost and let others figure out by themselves whether they find those differences worth it.

I was thinking of systems that are far more expensive, think several 100k. Arguments on car forums about dyno results cause all sorts of knicker twisting because of their variability.

Sammyw23

<reads thread scratching head>

So has anyone had issues with Stages indoors? haha

FWIW I have a quarq elsa and also train on a wattbike at work and the numbers "appear" in line with stages in terms of RPE. I never train to an exact number but a range and when doing so on either of the 3 I've never felt that I am working less/more on a particular one. All based on feel though so I acknowledge the limitations.

Stalin

RChung wrote:

frisbee wrote:

To be fair they are generally within a couple of % of each other, which is bloody good when you compare it to other far more expensive power measurement, for example car dynos.

Yes, but I generally try not to pay too much attention to expense when I do these analyses. That is, I know how much I'm willing to pay but I try not to presume that everyone is like me. So I generally just try to identify the strengths and weaknesses regardless of cost and let others figure out by themselves whether they find those differences worth it.

But since you bring cost-effectiveness up, training is one of the least demanding things you can do with a power meter. People have been able to train effectively without power meters for a long time, using nothing more than a wristwatch. That's because the power equation is so well understood that if you have a good wristwatch and a reasonably quiet road the correlation between power and either speed or time is extremely high. I just looked at the last 10 times I climbed a little nearby hill. Here is a plot of speed vs. power:



As you can see, the relationship is *very* consistent: there's only one odd point, and that's the "very windy day." If you exclude that point, the linear correlation between speed and power is .98 (and a linear fit isn't even the best thing to do because of the nonlinearity of the power-speed relationship).

So, if you're only interested in training, and you're not interested in accuracy but only in consistency, a wristwatch "is bloody good when you compare it to other far more expensive power measurement".

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

slowbike

Stalin wrote:

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

Although it'll be much harder to analyse the effectiveness of your training ....

Stalin

Slowbike wrote:

Stalin wrote:

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

Although it'll be much harder to analyse the effectiveness of your training ....

Would it?

Easy enough to set up a trainer to be repeatable. Easy enough to ride a known circuit or hill, easy enough to find an indoor track. Easy enough to do a TT and check progress against regular rivals.

Remember people did fine without power meters and people in other sports manage fine without a power meter up their arse.

But I would agree a power meter is the best way to measure power output. So if you want reliable power measurement you can always go to a gym with a Wattbike.

Obviously though if money is no object and you have the time to ponce about with a power meter, then using a power meter which gives reliable accurate power data for both legs is the best way to measure power output on the road.

That is when it is working properly.

slowbike

Stalin wrote:

Slowbike wrote:

Stalin wrote:

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

Although it'll be much harder to analyse the effectiveness of your training ....

Would it?

Easy enough to set up a trainer to be repeatable. Easy enough to ride a known circuit or hill, easy enough to find an indoor track. Easy enough to do a TT and check progress against regular rivals.

Remember people did fine without power meters and people in other sports manage fine without a power meter up their ars*.

But I would agree a power meter is the best way to measure power output. So if you want reliable power measurement you can always go to a gym with a Wattbike.

Obviously though if money is no object and you have the time to ponce about with a power meter, then using a power meter which gives reliable accurate power data for both legs is the best way to measure power output on the road.

That is when it is working properly.

Yes - much harder - as a stop watch has to be started & stopped manually, you'll never do it in the same place, if you go from a standing start you need to take into account accelerations. Stopping the watch after you've done a TT effort will be the last thing you want to do and it won't be accurate - if at all.
A stop watch doesn't take into account weather conditions.

Isolated TT's do not give you a good picture as it'll depend on the weather, any traffic, road conditions, how you've prepared for that event, even down to other competitors on the course. Do them more frequently and it'll help build a picture - but do you want to train for TTs or use TTs as training?

Doing fine and doing well are not the same thing - you don't need an expensive carbon bike to do fine - you could train on a supermarket special.

If you're just using a powermeter for the after ride analysis then perhaps you're not doing it right? Is it not of use during the training ride, does it not allow you to more accurately control your efforts during a TT - even on an unknown course.

Unless you're doing one legged efforts then the Stages PM will give you repeatable results without the need to constantly recalibrate (unlike some other systems).

Money isn't the answer to all things - all the gear and no idea?

Stalin

Slowbike wrote:

Stalin wrote:

Slowbike wrote:

Stalin wrote:

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

Although it'll be much harder to analyse the effectiveness of your training ....

Would it?

Easy enough to set up a trainer to be repeatable. Easy enough to ride a known circuit or hill, easy enough to find an indoor track. Easy enough to do a TT and check progress against regular rivals.

Remember people did fine without power meters and people in other sports manage fine without a power meter up their ars*.

But I would agree a power meter is the best way to measure power output. So if you want reliable power measurement you can always go to a gym with a Wattbike.

Obviously though if money is no object and you have the time to ponce about with a power meter, then using a power meter which gives reliable accurate power data for both legs is the best way to measure power output on the road.

That is when it is working properly.

Yes - much harder - as a stop watch has to be started & stopped manually, you'll never do it in the same place, if you go from a standing start you need to take into account accelerations. Stopping the watch after you've done a TT effort will be the last thing you want to do and it won't be accurate - if at all.
A stop watch doesn't take into account weather conditions.

Isolated TT's do not give you a good picture as it'll depend on the weather, any traffic, road conditions, how you've prepared for that event, even down to other competitors on the course. Do them more frequently and it'll help build a picture - but do you want to train for TTs or use TTs as training?

Doing fine and doing well are not the same thing - you don't need an expensive carbon bike to do fine - you could train on a supermarket special.

If you're just using a powermeter for the after ride analysis then perhaps you're not doing it right? Is it not of use during the training ride, does it not allow you to more accurately control your efforts during a TT - even on an unknown course.

Unless you're doing one legged efforts then the Stages PM will give you repeatable results without the need to constantly recalibrate (unlike some other systems).

Money isn't the answer to all things - all the gear and no idea?

I wouldn't wear a watch which cost less than a real power meter let alone a cheap toy like Stages.

You bought half a power meter because you are a cheapskate and a Sky fanboy.

charlie_potatoes

Stalin wrote:

Slowbike wrote:

Stalin wrote:

Slowbike wrote:

Stalin wrote:

If you are only interested in training there is another advantage in a wristwatch - you don't waste time faffing about with unreliable power meters and can concentrate on doing some worthwhile training.

Although it'll be much harder to analyse the effectiveness of your training ....

Would it?

Easy enough to set up a trainer to be repeatable. Easy enough to ride a known circuit or hill, easy enough to find an indoor track. Easy enough to do a TT and check progress against regular rivals.

Remember people did fine without power meters and people in other sports manage fine without a power meter up their ars*.

But I would agree a power meter is the best way to measure power output. So if you want reliable power measurement you can always go to a gym with a Wattbike.

Obviously though if money is no object and you have the time to ponce about with a power meter, then using a power meter which gives reliable accurate power data for both legs is the best way to measure power output on the road.

That is when it is working properly.

Yes - much harder - as a stop watch has to be started & stopped manually, you'll never do it in the same place, if you go from a standing start you need to take into account accelerations. Stopping the watch after you've done a TT effort will be the last thing you want to do and it won't be accurate - if at all.
A stop watch doesn't take into account weather conditions.

Isolated TT's do not give you a good picture as it'll depend on the weather, any traffic, road conditions, how you've prepared for that event, even down to other competitors on the course. Do them more frequently and it'll help build a picture - but do you want to train for TTs or use TTs as training?

Doing fine and doing well are not the same thing - you don't need an expensive carbon bike to do fine - you could train on a supermarket special.

If you're just using a powermeter for the after ride analysis then perhaps you're not doing it right? Is it not of use during the training ride, does it not allow you to more accurately control your efforts during a TT - even on an unknown course.

Unless you're doing one legged efforts then the Stages PM will give you repeatable results without the need to constantly recalibrate (unlike some other systems).

Money isn't the answer to all things - all the gear and no idea?

I wouldn't wear a watch which cost less than a real power meter let alone a cheap toy like Stages.

You bought half a power meter because you are a cheapskate and a Sky fanboy.

Oh dear. Here come the personal insults again :roll:

Poor form!

Stalin

I'm not being personal I'm having a go at all the other idiots who bought a Stages as well.

charlie_potatoes

Stalin wrote:

I'm not being personal I'm having a go at all the idiots who bought a Stages as well.

Disgraceful behaviour. Shame on you Trevor

RChung

Alex_Simmons/RST wrote:

But Robert was also suggesting that in general, guidance of intensity of effort, while really important wrt training, is a relatively low-fi application of a power meter.

Yup.

RChung

Sammyw23 wrote:

<reads thread scratching head>

So has anyone had issues with Stages indoors? haha

FWIW I have a quarq elsa and also train on a wattbike at work and the numbers "appear" in line with stages in terms of RPE. I never train to an exact number but a range and when doing so on either of the 3 I've never felt that I am working less/more on a particular one. All based on feel though so I acknowledge the limitations.

Your original post mentioned two things: drop-outs, and consistently low readings. Drop-outs are a symptom of interference. I've never run across a case where interference has resulted in consistently low readings: either you get nothing or you get intermittent but "correct" readings. If your "low" average is "consistent" then it's probably *not* due to intermittent drop-outs, so you may be riding on the trainer in a way that exacerbates bilateral asymmetry. So, first, determine whether the low averages are really consistent. If so, try to change the way you pedal on the trainer and see whether the average is still low and consistent.

[Edited to add:] If you look at the original DC Rainmaker review of the Stages, check out the trainer comparison. You can see that there were drop-outs but when the data weren't being dropped they were at the right power levels. This is what makes me think the drop-out problem is unrelated to the low average problem.

Sammyw23

RChung wrote:

Sammyw23 wrote:

<reads thread scratching head>

So has anyone had issues with Stages indoors? haha

FWIW I have a quarq elsa and also train on a wattbike at work and the numbers "appear" in line with stages in terms of RPE. I never train to an exact number but a range and when doing so on either of the 3 I've never felt that I am working less/more on a particular one. All based on feel though so I acknowledge the limitations.

Your original post mentioned two things: drop-outs, and consistently low readings. Drop-outs are a symptom of interference. I've never run across a case where interference has resulted in consistently low readings: either you get nothing or you get intermittent but "correct" readings. If your "low" average is "consistent" then it's probably *not* due to intermittent drop-outs, so you may be riding on the trainer in a way that exacerbates bilateral asymmetry. So, first, determine whether the low averages are really consistent. If so, try to change the way you pedal on the trainer and see whether the average is still low and consistent.

[Edited to add:] If you look at the original DC Rainmaker review of the Stages, check out the trainer comparison. You can see that there were drop-outs but when the data weren't being dropped they were at the right power levels. This is what makes me think the drop-out problem is unrelated to the low average problem.

Still no resolution on this - furthermore the issue has happened on the road now too. 10 mile TT last week, arrived and calibrated PM, readings looked high in warm up and so they were. Ended race with a 401w average....I WISH!!!

Back on the turbo three times since then and also rollers and still issues. I think you are right though it is dropouts rather than low readings but what happens is when the reading comes back in you get a big spike but overall the average reading is lower. Really don't know what could be causing it, there really is nothing in the kitchen that could be causing interference so I am at a loss.

I read last night about the battery contacts getting squashed down which can cause issues and also battery quality - so I am going to check the contacts, put in top quality battery and see how it goes in Sundays race.

If no change, its going back for crank no.3! 3rd time lucky or I think I will give up on Stages