L/R imbalance - stronger leg is the weaker side?

Back in January, I started the 30 hour power balance trial period that P2M was giving everyone. Found that unless I consciously pedaled differently, my balance was typically 55/45. After a couple weeks, I lowered my saddle 5 mm and slid it back 1 cm to unweight my arms a bit and improve stability (was feeling like I was sliding forward on the saddle, which was all the way forward). It improved the fit, and interestingly enough, with no other changes, my power balance ended up 51/49 or 50/50 after that. Unintended consequence that I found interesting.



I had the same thing, and with Assiomas.

Looking around various forums, this is a common finding with Assiomas, and it’s always the left leg that’s stronger. I have heard it theorised that’s because the left pedal is the master, and it takes the right a couple of revolutions to ‘catch up’, which adds up over the course of a ride. This is supported by the fact that the imbalance is always worse outside than inside (no stopping and starting inside, in theory).

So I’m not saying there isn’t an issue, but too many people report this exact observation for it to be a coincidence, IMO.


My max left right imbalance is around 47L/53R (Assioma Duo) with my right leg being my dominant leg off the bike. . It does vary both over a ride and between rides, but always with the right higher than the left - unless I’m out of the saddle when my balance becomes exactly 50/50 presumably because I shift my entire weight onto each pedal in turn.

I should add I have been slightly unlucky in that I am on my third set of Assioma pedals - the reasons for that don’t matter here but I can say that all three sets of pedals have agreed on my L/R balance measurements.

I really need to measure mine some day but I wouldn’t be surprised if it changed quite a bit day to day. My right leg is strongly the dominant one and when I am not spinning well/freely I suspect the left struggles to deliver power and the balance could be as much as 40L/60R. But on other days when everything is spinning well/freely the balance will be 50/50 or maybe even to the left. Then again I could be wrong and it just feels that way :thinking:

To be honest the more I think about it the less surprised I am that people find that their dominant leg is the weaker on the bike.

Left/right handedness is more a feature of dexterity and coordination than directly related to strength.

So for arms it makes sense that the dominant arm gets stronger as you are most likely to carry and move things with it day to day.

For legs I’m not sure this is true? The leg which you are most coordinated with could do less heavy lifting day to day than the less coordinated one. The snowboarding and football examples above are extreme examples but even simple movements like setting off to walk could mean one leg does more work than the other day to day even if its not the dominant one.

I too, am on assioma duo with a 55/45 balance. Right leg is my dominant leg and measures larger from ankle to hip but accounts for only 45% of power output. Weird. But I also think there may be other things working here.

When I dig deeper into my cycling dynamics from Garmin, I see my right leg (weak cycling leg) my right leg ALWAYS has a lower Torque Effectiveness score and a higher Smoothness score. What does this say? I think it means my right leg stomps and my left leg spins better circles. Maybe applying less power over a longer pedal stroke leads to more overall power production.

Worth noting my right side sweats way more than my left and I seem to carry slightly smaller love handles on the right side. Right arm is larger/stronger than left arm, but I’ve often wondered if the right leg carries more fat and that is why is is larger? Right calf is way more vascular than left calf. Finally, I’m a triathlete with nearly 50/50 ground contact time while running, but my shoes wear in distinctly different ways left vs right foot.

Mine is the same but on P1s and now P2s. Same with running as well as left foot is flatter and right foot wears towards the outside.

I’ve been in the sport for 20 years and I think where this developed for me is pitching through early college in baseball (and hitting) with weight shifted back to right side. I never worried about it but over the last 5 years I’ve started to develop more issues through the low back and hips due to the twisting that’s been further ingrained with the repeated motion of cycling and running.

I’m now with a PT trying to undo what I can and stabilize everything. While there likely isn’t an issue with people being 48/52 or 51/49 and all of that jazz, I heard Colby Pearce note on multiple podcasts that when people start to get to that 54/46 range it’s time to start investigating - I think he’s right.

Same for me, which surprised and puzzled me when I found out. I had assumed my dominant right leg would put out quite a bit more power but the reverse was true - ~ 47-53%. By concentrating on alternate legs during most TR workouts (particularly threshold and above) I’m slowly closing the gap.

Another Assioma Duo user reporting in: the biggest difference I get is 56/54… but usually closer to 52/48.

I attribute it to a hip issue on my right side, though that’s self-diagnosed, and we know how accurate self-diagnoses are. I try doing a lot of stretches for my hip and sometimes can get 50/50, but very rarely.

I’m another user stumbling over the left/right problem with Assioma Duo (Shi). 3 months ago I had a cartilage surgery - 8 weeks of crutches so I’m just 4 weeks walking without crutches.
My left leg is too weak to walk down stairs without a handlebar. I can walk up with some pain. My left tigh is about 4cm less circumference than my right, while my upper leg is a staggering 8cm less circumference. My right leg has been much better since years - as my left leg suffered already 3 ACL replacements, meniscus tears and well now lately 8cm² of replaced cartilage. Plus there is still bone bruise and minor swelling.

My first ride was 50/50 after which I contacted Assioma and they sent me the following info (nothing personal in it so I think it’s fine to publish):

I checked the status of this Assioma DUO remotely - when a new ticket is opened and the sensors are connected to the app Favero Assioma we are able to check some internal parameters of the sensors - but I wasn’t able to see any data after the submission of the ticket.

In this case, in order to better understand the situation, I would kindly suggest following these steps:

- reinstall both pedals being careful that the sensor is not touching the crank and try to add at least one washer for each side (please see Chapter 7. Fixing the pedals to the crank-arms at the following link: Manuals - Google Drive);

- verify that the cleats don’t make contact with the sensor;

- perform 2-3 calibrations through the app making sure that the bike is steady and the shoes unclipped from the pedals;

- do another short ride session including some hard sprints and progressions (for a correct mechanical adjustment);

- disconnect and connect again both sensors so that I receive the latest saved values.

In addition, would you be so kind as to send me some pictures of both pedals (installed on your bike) following the instructions in the attached PDF document?

Finally, in order to complete my remote analysis, I kindly ask you to temporarily set your Assioma DUO as Assioma UNO (using the app Favero Assioma), to perform other 2-3 manual zero offsets, and to have a ride.

Please let me know the results of the suggested operations and if Assioma works correctly when converted into Assioma UNO.

I replaced the default sram spacers on both sides with the Assioma ones which are a tiny bit thicker - the distance should be okay however. The sram spacer on the Force 22 cranks can now nearly fit into the gap (or better it fits 3/4 of the way around). The cleats/shoes are a long way in the distance so no contact either.
I re calibrated the pedals 3 times and went out for a long ride - though without any sprints.
I don’t understand why they cannot see my data - as I recalibrated with Assioma app, I wrote the ticket using my PC however (after finding out the pedal serial numbers by connecting the pedals in the app)

The pedals now went from 50/50 to 47.2/52.8 on that ride on average. I hope I can find a friend without muscle disbalance to try my bike - problem is most I know here have Looks or are vastly different size from me so we cannot just switch bikes for a couple of km, while the one Shimano user I know also has weaker left leg…

On power above my FTP the balance goes to like 55/45 while it goes to 50/50 while cruising with below 50% FTP. I do wonder how the balance is calculated too - because standing/not moving will be 50/50. So does Garmin or Jepster App (both show identical values) take the time not moving, descending without power on the pedals into the average? Then it would actually be ~45/55 (adding descending time and so on) or ~43/57 (adding time on lunch break - it was a 7 hour ride including 1 hour break).

Seeing that on actual power like squatting my right leg is like 3-4 times stronger than my left leg for right now - I still kinda doubt those balance numbers. I would have expected something from 40/60 to 30/70.

I haven’t done the short ride with proper sprint and progression however yet. My max was once 622w, I guess pushing hard for a soon to be red traffic light, and max over 2 minutes was 270w (I’m 67kg and had little training last year due to my knee so the overall numbers right now seem to align quite well, had 142W weighted average power for the 6 hour ride / 127w avg power and guess my FTP is around 195 or 3w/kg or so right now hoping to be back at 4w/kg in 3-4 months which was my level 1 year ago before the knee problems started). I find it hard to believe that the right leg would be another 20% stronger as the overall wattage would be overstated then.
I bought the Assioma’s exactly for tracking my recovery progress. Seeing how bad I still walk or limp around, cannot even thing of jogging, or walking down stairs normally, this 47/53 number looks pretty suspicous.

I don’t have a double sided power meter just a left sided pedal one but my garmin reports it L/R. Typically for me indoors with a minor by comparison leg imbalance (the right is also dominant) I get just 82% of the power according to Garmin on my left only power meter 0% on the right (because there is no power meter). So I think that my good leg is contributing 18% towards the power measured on the left. (Which I think will vary according to how smooth you are). If my theory is correct :thinking:, using my theoretical 82% and using your 47/53. Your imbalance could be something like (0.82x47= 38.5) Left/ 61.5 Right.

1 Like