Stages L power meter, worth having?

[Broady]

I've got a L Stages, no complaints. I know from my turbo that my LR balance is pretty much spot on so it does the job for me.

[shotgun1]

I've been using single sided PMs for at least 6 years via (Garmin, Assioma and Stages) fitted to a couple of bikes, and I just switched to a double sided PM that came with my Red AXS this year. I don't now how variable L-R power is for other people, but after 3-4 months of use i'm at 50/50 spot on. So having just a L PM should suit me fine.

[tritiltheend]

I can certainly see the logic behind it. I'm just wondering how big of an issue it would be in real life and for how many.

I have really no clue as to how dominant one leg is vs. the other on average. Is it 1%? Is 5% normal or is that extreme? Or would 99% have less than 1% difference?

The same in the different zones. If you are 3% off at FTP is it then even possible to be 10% off at FTPx2 or is that normal? Does it change much as you are getting more tired?

If everything is reasonably stable across does it then matter in the end if the values are off? If I got one dominant leg meaning values are 3% off which then becomes 6% off, but it is more or less the same at FTP or FTPx3 then I guess I would just naturally adjust my training accordingly?

I haven't thought much about the issue before I saw this thread. The only comparable values I got for myself are on my Kickr and they are reading so closely I couldn't really tell which one is which one across datasets. That doesn't mean that my Stages reading are correct of course and I couldn't say if that is uncommon.

If your Stages and your Kickr match, that gives you some hope that you don't have a power balance issue but it's not a guarantee as Kickrs have been also known to be innaccurate. Have you done an actual comparison of a ride capturing both at the same time? You can capture the Stages to a Garmin or Wahoo head unit, and your Kickr to Zwift or whatever platform you use. Ideally you should look at a variety of durations of power as well as average. For more detailed analysis I use Golden Cheetah but there are other tools, DC Rainmaker has a tool on his website.

Not specifically in response to you, but a few more thoughts on leg imbalance. I did a quick search and didn't come up with any hard data on how common this issue is. On a thread on another forum five of us chimed in with hard data showing significant leg imbalances. Proves nothing but I don't believe these issues are as rare as some make them out to be. DC Rainmaker has in the past has been pretty tolerant of single sided power meters and shown fairly close leg balance for himself, but his recent review of the Quarq Rival single sided power meter showed lots of innaccuracies, and his best guess was that he was testing it on a bike that was a bit too small and that caused a leg imbalance. And there has been no followup to that review with a resolution of the issue.

I did find the actual data for the two short rides in which I ran a Stages and my Quarq at the same time and it's instructive as to how complicated this issue is. A simple corrective factor would not work as the difference between low power and high power was much higher than I remembered:

Ride 1, 22.7 miles
Quarq average power: 116
Stages AP: 128
10.3% difference.
Quark 1 min power: 232
Stages 1 min power: 229
-1.3% difference.

Ride 2, 23.6 miles
Quarq AP: 156
Stages AP: 174
11.5% difference.
Quark 1 min power: 252
Stages 1 min power: 255
1.2% difference

I've also seen others post data that indicated that their power balance not only varied with intensity, it varied with level of fatigue as well.

I'm older and stay in shape year round. My critical power varies less than 10% from winter to summer. So for me this variation is huge. I also have eight years of comparative data that would be rendered meaningless by a power meter than was 10-12% off on average power. If you acquire a new power meter that reads significantly different, you won't know if the difference is your fitness or the device. I have two power meters and a smart trainer. If those devices don't match then they are effectively useless to me.

Again, if you have a way of verifying across a variety of intensities and levels of fatigue that you do not have a leg imbalance, then single sided is OK. But most folks have no way of verifying this. Many of us spend lots of money on lightweight or aero goodies, that greatly dwarf the difference in price between single sided and double sided power meters.

[tritiltheend]

Thanks for all the responses guys.

But the point you're missing is that if you only have one power meter on one bike then it's totally irrelevant whether it's single or double sided. As long as it consistently measures that power then it's relevant for the user to use. You can then compare power meter numbers from one ride to the next and from month to month. Consistent, reliable measurement is the most important factor.

I think c60rider makes a valid point here, it will be my first and only experience riding with power so as long as it tracks consistently I have nothing to compare it against but will still see improvement with these figures no matter how accurate/inaccurate they are. However, part of me doesn't want to 'settle' for what almost seems like a make do method. Although it will undoubtedly give me figures to work with it seems like more of a ballpark than real world figures.

There are great arguments for and againt I guess. Perhaps I will wait a while longer, I've ridden for many years without power so it's hardly an issue at this point. Maybe I could hold out for the Garmin Rally to come down in price a bit (not any time soon) or save a while longer.

As I just posted, the consistency argument only works as long as you only use that one power meter. Once you switch to another power meter or acquire a second one, any significant variance between them will mean you won't know if the difference is the device or your fitness.

For only slightly more than a single sided Garmin Rally, you can get the Favero Assioma Duo, which is very highly regarded and used as a reference device by DC Rainmaker and GP Lama. Hopefully Garmin has sorted out their problems but they have had a lot of reported issues in the past, and my anecdotal experience with folks I know is not at all encouraging, a number of reliability issues and some clearly bad data. My wife has a pair of Faveros and they are verified accurate and have been solid so far. If you want them for MTB use that's another matter. The Faveros are Look-compatible (although they just introduced a Shimano SPD-SL compatible spindle). You can convert them to SPD, (search for Favero SPD hack), but I wouldn't use them for hard core MTB use due to the vulnerability of the large pod.

[AJS914]

I have a Stages L and I use it successfully. I honestly just don't see how these differences make much difference in the real world. I train in the ballpark of zones. I test my FTP. 90% of my riding is around Zone2. Sometimes I do some tempo. I do short sprints which are max. Most intervals are max in the 3-5 minute range at max.

[HenryH]

I can certainly see the logic behind it. I'm just wondering how big of an issue it would be in real life and for how many.

I have really no clue as to how dominant one leg is vs. the other on average. Is it 1%? Is 5% normal or is that extreme? Or would 99% have less than 1% difference?

The same in the different zones. If you are 3% off at FTP is it then even possible to be 10% off at FTPx2 or is that normal? Does it change much as you are getting more tired?

If everything is reasonably stable across does it then matter in the end if the values are off? If I got one dominant leg meaning values are 3% off which then becomes 6% off, but it is more or less the same at FTP or FTPx3 then I guess I would just naturally adjust my training accordingly?

I haven't thought much about the issue before I saw this thread. The only comparable values I got for myself are on my Kickr and they are reading so closely I couldn't really tell which one is which one across datasets. That doesn't mean that my Stages reading are correct of course and I couldn't say if that is uncommon.

If your Stages and your Kickr match, that gives you some hope that you don't have a power balance issue but it's not a guarantee as Kickrs have been also known to be innaccurate. Have you done an actual comparison of a ride capturing both at the same time? You can capture the Stages to a Garmin or Wahoo head unit, and your Kickr to Zwift or whatever platform you use. Ideally you should look at a variety of durations of power as well as average. For more detailed analysis I use Golden Cheetah but there are other tools, DC Rainmaker has a tool on his website.

Not specifically in response to you, but a few more thoughts on leg imbalance. I did a quick search and didn't come up with any hard data on how common this issue is. On a thread on another forum five of us chimed in with hard data showing significant leg imbalances. Proves nothing but I don't believe these issues are as rare as some make them out to be. DC Rainmaker has in the past has been pretty tolerant of single sided power meters and shown fairly close leg balance for himself, but his recent review of the Quarq Rival single sided power meter showed lots of innaccuracies, and his best guess was that he was testing it on a bike that was a bit too small and that caused a leg imbalance. And there has been no followup to that review with a resolution of the issue.

I did find the actual data for the two short rides in which I ran a Stages and my Quarq at the same time and it's instructive as to how complicated this issue is. A simple corrective factor would not work as the difference between low power and high power was much higher than I remembered:

Ride 1, 22.7 miles
Quarq average power: 116
Stages AP: 128
10.3% difference.
Quark 1 min power: 232
Stages 1 min power: 229
-1.3% difference.

Ride 2, 23.6 miles
Quarq AP: 156
Stages AP: 174
11.5% difference.
Quark 1 min power: 252
Stages 1 min power: 255
1.2% difference

I've also seen others post data that indicated that their power balance not only varied with intensity, it varied with level of fatigue as well.

I'm older and stay in shape year round. My critical power varies less than 10% from winter to summer. So for me this variation is huge. I also have eight years of comparative data that would be rendered meaningless by a power meter than was 10-12% off on average power. If you acquire a new power meter that reads significantly different, you won't know if the difference is your fitness or the device. I have two power meters and a smart trainer. If those devices don't match then they are effectively useless to me.

Again, if you have a way of verifying across a variety of intensities and levels of fatigue that you do not have a leg imbalance, then single sided is OK. But most folks have no way of verifying this. Many of us spend lots of money on lightweight or aero goodies, that greatly dwarf the difference in price between single sided and double sided power meters.

Thanks. Excellent post.

Yes. That is exactly what I did. I can't remember the average power difference, but it was a couple of watts. More importantly for me during higher loads in let's say 3-8 min intervals they are close enough so that they work as in me wanting to run 300, 400 whatever watts for X minutes. Outside doing 300 watts for 15 mins I can't hold 300 watts exactly anyway so there are a million ways that I can't train that specifically. Meaning if my leg dominance is influencing things a couple of % it is not a huge deal for me if I'm doing 290 or 310 for those sessions (it would be if we are starting to get to numbers like 350 or 450 if the intention is to do around 400). Actually it doesn't matter I would argue as I always adjust that kind of training to what I have done in the past, where I am in my training "cycle" etc. The key would be that the PM is consistent over time more than anything else. For someone only having one PM I guess that would be the most important thing anyway (within reason)? A lot trickier I could imagine across bikes.

Could there be other ways that average watts might end up being off than just leg dominance? I have no idea if that is a ridiculous idea, but could they have different "tolerance levels" (I wouldn't know what to call it) when power goes up, down, off and on?

Personally I don't really use average watt through a full ride for anything. That might just be me though.

[AJS914]

I do use average watts per lap during rides for intensity control. For example, if I want to stay in Zone 2, I'll start a new lap and try and keep the average power around a certain amount. I'll try and not exceed threshold on climbs. If I wanted to do a 10 minute tempo interval, I'd start a new lap and look at average power for the lap. I live in an undulating area so steady state power is hard to achieve.

[battlehard]

Interesting. Any links to datasets showing that the difference between the two legs are that big?

I have only had one sided (Stages) and I have always thought there wouldn´t be much need for dual.

For the OP - anecdotally mine has been excellent. Only small issue has sometimes been that the battery goes flat after cycling in the rain. During the ride no issues, but occasionally the day after the battery will be dead. Happened 3-4 times over some years. I can´t remember which generation I got, but it isn´t the first because I believe they redesigned the battery cap for the version I got. Not sure if they have done further upgrades since.

Not something available right now (on my phone), but remember say you pedal at 50/50 balance at threshold and your balance changes to 45/55 when you do a 4 min interval at 400W say, the difference in power is 40W. If you prescribe your intervals as percentage of FTP this will determine if you can make the interval or it lasts 2-3 min. 2-3% fluctuations are fairly common just riding along, but 5% l/r fluctuation when really pushing hard is nothing special either.

Sent from my LYA-L29 using Tapatalk

Have a look at this with Sir Chris Hoy, 47:45 ish left leg right leg numbers

https://www.youtube.com/watch?v=h7l9k_EmNq0

[tritiltheend]

Could there be other ways that average watts might end up being off than just leg dominance? I have no idea if that is a ridiculous idea, but could they have different "tolerance levels" (I wouldn't know what to call it) when power goes up, down, off and on?

Well, of course there could be measurement inaccuracies in the device itself. Fairly common in smart trainers but not unheard of in power meters as well. In my case I am certain it's L-R power discrepancy as the error in the Stages matched the L/R balance numbers I've seen in my other power meters. And those other power meters show the same pattern; the discrepancy is high at L1-L2 and readings from both sides converge at higher power levels.

I don't claim that my leg imbalance means that everyone has the same issues as me and can't use a single sided power meter. But those who get good results from single sided meters can't claim that means everyone one else will. And many of them don't have a reliable way to verify if they are actually getting accurate numbers. Between having done calibration with a known weight and having had in our household as many as 6 power meters at one time and 3 smart trainers, it's very clear what's accurate and what isn't. And BTW, only one one of those smart trainers is accurate (Saris H3). Not accurate include a Computrainer (with careful calibration OK for averages but not shorter intervals) and a Kickr Snap (junk numbers regardless of calibration).

[cfrankscid]

All really interesting responses. The other factor here, which affects me at least, is mental. One of my bikes is Stages one-sided power only and I actively focus on ensuring I'm pushing with my left leg to keep my power consistent and high. On my Quarq bike this is obiously not an issue.

Probably just me being mentally broken, but this annoys me more than any potential data discrepancies.

[tritiltheend]

Just one more point to add, now that I'm thinking back to when we did the test with the Stages. My wife's numbers were also very inflated. But at the time she was dealing with a minor but persistant right leg muscle pull that took many months to resolve and significantly affected her leg balance.

So if you have any kind of injury during your training that affects a leg, even a relatively minor one, a single sided meter will not accurately show the effect of the injury and you will not be able to monitor the status of your recovery process. If the injury is to the left leg, it will overstate the effect of the injury, and if it's to the right leg, it will understate the effect of the injury.

[iamraymond]

My 4iiii left sided PM tracks very well compared to my Elite Direto smart trainer. I'd say a one-sided PM is fine as long as you understand it's short-comings.

[bilwit]

Whatever power discrepency you may or may not have between L/R is largely irrelevant because your results are normalized to the number you're given, such that all your power numbers will be "correct" relative to both yourself and the same device. There may be a slight difference when comparing it with another source, but it will be tiny--not enough to wildly change your power zones.

My first power meter was Stages and I used it for years. I also used Kickr power over it when on the trainer. No big deal. I eventually moved to a Power2Max and then Quarq to chase grams (crankset/axle as a whole) but otherwise I was happily content with Stages. Power is better than no power.

[raggedtrousers]

I had a 4iii Ultegra. It worked fine.

I now have Assiomas (duo). Pretty much a year of constant use has shown the following:
1. In z2, when I'm not fatigued, I'm 53-54% left leg dominant.
2. As I fatigue, or move to threshold, that moves progressively towards 50/50
3. When I'm right at my limit, I'm very slightly R leg dominant.

Now the question is, what do I do with that info?

About the only time I could see it being an issue with the 4iii is that it apparently overestimated power during the first hour or so of a z2.

I can see that being a potential problem, but in practice it never was, possibly because my wahoo also displays HR and I have a fairly good idea how the two correlate.

All things being equal, I'd say 2 sided power is obviously better, but if budget or availability only runs to a single sided, it'll do the job.

[sinfjotli]

I'd say that if the only thing that prevents you from getting the Assioma Duos is Look-style cleats, you should just give them a try (maybe with some cheap Look pedals - you get extra cleats that way). The Shimano cleats are slightly better but Look cleats are fine, they do the job. Or get Quarq/Power2Max and use any pedals you like Without knowing that you DON'T have an imbalance, there is no way of knowing if left-sided power meter is enough for you, especially for threshold/VO2Max intervals where a few percent inaccuracy can really change the nature of the workout.