Left right leg imbalance - easy gains?

I had an SRM, and now have a Quarq so for first time I can see L-R imbalance
It’s pretty good at 48-52, but still; maths shows at my FTP right leg is 15 watts more than left
So all thinks being equal just getting left leg as efficient would be a 15 watt bump; which would be much harder to do with aerobic gains at my age !

Would be interesting to see if there was broad data that showed ‘bins’ of L-R distribution and if that changed vs atheletic pedigree?

I had about the same imbalance before I started a 6 month bout of serious training. Interestingly it disappeared by itself without any specific intervention. My coach mentioned it to me and said it was a good sign of my fitness. I wasn’t doing any core work at the time. I think just doing more volume, interval training, racing and lots of riding in hilly country made the difference.

I think now in hindsight some core work would have helped because my core was definitely in better shape from the riding I was doing

Are you goofy footed, or natural?
There should be a poll for this in relation to leg imbalances.

How does that affect imbalance?

I’ve always wondered if this made a difference actually. I’ve noticed that I always lead with my left. Therefore I feel like when I coast and then start pedaling again that initial pedal stroke is a bigger spike on the left.

When it comes to my r/l balance, in more steady state I’m something like 49/51 but when riding in a group with more variations in cadence etc it opens up to 46/54 or so. Could be something else entirely… idk.

Depends on what your limiter is. If cardio - no, you won’t see an FTP increase. If muscular, then maybe yes.

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You jumped through a lot of assumptions really quickly there to arrive at a conclusion.

Let’s just test the facts;
You didn’t list which quarq you have, but most are accurate to 1.5%. So right off the bat you are right on the edge of the margin of error for the device itself.
You also must be a monster, because if reducing a 2% margin gets you 15w, you’re sitting with a 750w FTP. What you likely meant was your FTP was 325 and that means 6.5w…again, assuming margin of error.

Your final comment is the most important, and I can’t find the discussion that took place on it here, may have been on the FB forum before this site properly launched. There was a study that had the distribution of L/R, long story short 1) there was nothing conclusive showing 50/50 was optimal, and 2) most people fell within a +10/-10 distribution and that was entirely “normal”.

You can work on an imbalance if you think you have it. Single leg drills both in the gym and on the bike. Though 52/48 I would not classify as an “imbalance” by any stretch.

I think the assumption is that if you lead with a specific foot when coasting, any time you resume pedalling there is greater force required on the initial stroke, which could skew the data. Ex. if you’re in a group riding rolling turns, you can coast in pack, then every time you pedal again you put more force on one side which could skew data.
I dont know if i fully agree with the assumption, given every hour of riding is ~5,550 revolutions, so having even 50-100 of these type of events should not have a meaningful impact on the data.


Power imbalances may have more to do with leg length discrepancies than simply dominant legs.

I thought I was just right leg dominant (which I am). I surf regular footed and I always thought my right leg was simply stronger. Turns out my right leg is a little under a cm shorter than my left leg.

Shimmed my right cleat, power split is typically 50/50 now. Sadly, FTP is going nowhere.

Interestingly my leg length difference disappears on efforts above ftp. I will still see about a 51/49 or 52/48 l / r split on easy rides but any effort above 300 watts and I’m a dead even 50/50 all the time.


Recommend a good bike fit which should include a full physio exam.


If I read this correctly, you’re asking about this after a single ride with the quarq? If so, you need to watch this for a while before deciding if it’s worth your time. I vary from 48/52 to 52/48 depending on the day, the wind, the phase of the moon, whatever. More often than not I’m 50/50 or 51/49. Watch it over time, and if you consistently see that difference, maybe it’s worth your attention… but probably not either way.

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pedal one legged and I bet it isn’t 0-100. The imbalance measure seems useless when it comes to practicality IMO


Agreed… I count the L/R balance measurement as proof that I don’t need a dual sided power meter to measure L/R balance.


i thought it was going to be the most amazing thing ever, got it, never bothered to look at it after the 2nd or 3rd ride.

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My left leg is slightly longer as broke my right a few years ago on motor bike. As such I’m left dominant quite a bit.

Working on fixing it as finding left knee issues from overuse after moving from desk job to one where I’m standing all day.

Think I’m getting it sorted with cleat positioning, shins and core work.

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yeah, not needed

I believe all Quarqs has a single measurement point (the crank spider), so the error between each leg will be closely correlated, i.e. a 1.5% error will be seen equally and in the same direction for each leg. This is different than other dual-sided power measurements, where each leg is measured separately, such as pedals. It that case the error is not necessarily correlated, and your statement would be true.

It is actually a 4% margin. Lets assume 52/48 split on 100 watts to make our math easy:

52x100 = 52
48x100 = 48
difference = 4 watts.

So a 15 watt difference with a 52/48 split is 375 watts. Still an FTP I cant even imagine, but not 750.