Left / right power balance

Did my first ride today with a power meter (Vector 3}. My power balance was 54% left 46% right. Is a power imbalance normal? What should I do to correct the imbalance?

In short, probably nothing to worry about. It’s a mistake to assume that you are 50/50, or even that you need to be. We are not machines and can’t expect that level of control or precision.

You have data on a single ride. If anything, you should track it over time and see what trends develop. It’s totally common for it to vary with different power levels and as fatigue builds.

Sometimes more dramatic differences warrant works and that is it’s own mess. Unless you are having real problems (pain and such), you are merely learning that you likely had this the whole time.

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Thanks @mcneese.chad no pain or any issues, just curious!

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Try riding no handed on the trainer with the stats shown and see if they change. I’ve noticed my left/right balance can be down to 30/70 at times (broken clavicle) when seated, but that balances back at 50/50 when I’m no handed. It’s not a scientific test, but could help narrow down the problem area.

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not an issue , is it also like this at higher power ?? i find my L/R balance is further of if i ride at 50% FTP compared to 120% FTP . Do you see the same ?

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I have a 54/46 imbalance which evens out as both power and fatigue increases. It makes it a challenge matching power on my single sided power pedals with my turbo.

The only issue would be if you only had a left sided power meter and didn’t realise you had an imbalance. For instance, I was using a 4iiii left sided power meter earlier this year and kept failing VO2 workouts. It wasn’t until I bought a smarttrainer that I could see that there was a rather large power difference above FTP. I was probably doing 130% intervals instead of 120% intervals and thus failing to complete the workouts. It seems my left leg works more at low power and then there’s a range where both work roughly the same then my right leg works harder at a higher power output! I’ve turned power matching off and just use the smarttrainer during workouts.

I only use left-sided power meters on my MTB’s so getting the Favero Assioma Duo’s was a confirmation on what I suspected, that my left leg is weaker than my right. I use a Tacx Neo when training indoors and I’ve made comparisons between my PM’s and that before rendering about 4-6% lower reading from my left-side powermeters.

EDIT: I have 47% left / 53% right balance.

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This is a red herring. It doesn’t matter if you have an imbalance and use a single-sided power meter, as long as you use it consistently, and against itself. You are effectively using the same tape measure to set your zones and execute your training, and it works great.

There CAN BE an issue if you attempt to take your power numbers from that device and use them with data from another device (different trainer or power meter). But that caveat exists for ALL power measurement devices.

If you use more than one, you should evaluate the potential differences in their readings.

But to reiterate, there are no problems using a single-sided power meter against itself, regardless of power asymmetry of the rider in all but the rarest of cases.

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The problem (with a single-sided meter) is if your imbalance varies with power. If you’re balanced at 120%+ of FTP and significantly imbalanced at/below FTP, your zones will be different than you think they are.

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54/46 is probably on the higher end of normal, but there’s really not much you can do about it anyway. Start to worry if it tracks upwards over time, which is likely indicative of an issue with one side of your power meter. I logged 73/27 on one ride, which was a pretty good indicator that my left leg had grown by six inches overnight… or just that the right pedal wasn’t transmitting properly… (also running Vector 3). Frankly, that’s the best use of L/R power balance I’ve found so far - diagnosing power meter issues!

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And in these cases, it is usually something that’s been noticed or diagnosed earlier in their life, or caused by some traumatic injury along the line. I’ve not come across someone who just has one leg significantly weaker or less contributory than the other without also having a recent (fairly major) injury. I dislocated my foot about 17 years ago, and had a major strength imbalance between my legs, but that was rectified over the course of about 12 months and a whole ****load of lunges and single leg squats.

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I just installed and had my first spin with Assioma Duos today.

I suspected I had some LR imbalance, but was surprised that it was as high as 55/45. Also, the left pedal reporting a significantly different power than my left-only Stages.

I’m going to spend a few more rides to get to grips with the data and see if there if this continues, before deciding on a course of action.

My point is you can’t set zones accurately if there is variation in your imbalance. You might get some zones right but others will be out by quite a margin. As mentioned, for me it meant that what I thought was 120% ftp was in fact closer to 130% given that my right side takes on more and more of the strain the further I go above ftp. A sure fire way of failing workouts or burning out!

I had 2 PMs and a computrainer, one being a single sided. I vary between 52-57% left side power dominance due to a repaired right ankle from an old peroneal tendon dislocation that has never recovered its total range of motion or stability/coordination so my ankling on that side is not as good as my left despite lots of PT. This is shown in my torque effectiveness and pedalling smoothness metrics which are always lower for the right leg. There was always a huge variation from day to day due to varying levels of fatigue going into the ride and what the ride consisted of(mostly outside with different routes) even if I was trying to do similar intervals. One of my power meters was single sided and I could never get it to agree with the computrainer or the other crankbased powermeter consistently so I just got rid of it and went to dual sided(same brand) and suddenly all my numbers were a lot closer regardless of the workout. So single sided might work for some but for others even slight deviations can manifest if you don’t use it 100% of the time and even then its potential introducing conflating factors in the power numbers reported

This is true, but again, you have a diagnosed condition/previous injury. Most people anchor on a power imbalance that might be 4% one day, 2% the next, when their power meters aren’t that accurate to begin with. Unless you know you’ve got a serious imbalance for a specific reason (different leg length, injury, other condition), L/R balance doesn’t really provide actionable data, and certainly not one where most people need to drop extra money on a dual-sided power meter.

That said, I have a dual sided power meter. :laughing: And what that dual-sided power meter has taught me is that I don’t need a dual-sided power meter. :man_facepalming: YMMV.

Have a look at other threads on this topic. There are quite a few. Many are dismissive of the issue - I am not. As a time trialler I find I have an imbalance as reported by my dual sided vector 3s when my position gets deeper. I loose power on the right hand side and it drifts from bang on 50/50 to 53/47 or so. So I do a lot of work on position and hip flexor strength.

I think this does matter because a 6 percentage point difference is actually a 12% difference between 47 and 53. That said I did a 50m TT last weekend in a big PB and it was 52/48.

Try different positions. Sitting up, at any power I am pretty nearly always 50/50. Road bike - pretty nearly always 50/50. TT bike can vary from 50/50 to 53/47 depending on position.

Do make a point of recalibrating the vector 3s before each ride. I find there is more likely to be an imbalance if I have not recalibrated than if I have, but i think it is a contributing factor, not the real underlying reason. I know when my hip flexors are playing up. :slight_smile:

Don’t stress or worry about it. Treat it as “Oh that is interesting - I wonder what might be causing that?” and do some experiments to see what you find out. A TR session just sitting up, on tops, or on the drops, or swapping position every interval and look for systematic differences (Take notes which ones though). That would be my advice.

Contrary to what was said above, I find L/R balance gives me actionable data. But look for trends rather than getting worried about point information.

I hope that helps.

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This is fair. If you can drill down to that level of granularity and identify issues with fit based on specific rides or segments of rides that show a different trend over the course of time, THAT would be actionable via either strengthening or (more likely) fit issues. I agree that there is limited value in one-off rides.

Again, though, we are often talking about differences in power that are often within the tolerance of the power meter itself. So while I agree that in specific cases such as yours (a single specific position held over long periods done repeatedly) or others (injury) where there might be data that’s at least interesting, or at best actionable in some way, whatever actions or corrections that are applied because of this data are very much in the margins in most cases. The higher the level of competition, the more value there will be in chasing those kinds of rabbits.

My point in being dismissive is that I’ve seen discussed here and elsewhere by average/recreational riders their 53/47 power imbalance and what they should do to correct that. In fact, early in the season, I was often 53/47, and simply through the normal process of training it is rare that I am anything but 51/49 now paying zero attention to it. Being dismissive of this is merely to caution losing the forest for the saplings - that is these power imbalances are rarely limiters.

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The thing is a didnt know I had a power discrepancy. I worked hard to get the right leg back to what felt like normal and I can run/rock climb/splitboard just fine on it. Before powermatch the trainer power and single sided power meter never matched and always seemed inconsistent with rpe day to day which I was just attributing to a combination of spindown and zeroing errors withing the range of calibrations for both devices. Wasnt till i got a new power meter on another bike that I started using on the trainer did the numbers start tracking well together even though there was always a small offset. Doubling the left side power was doubling to tripling the error. Its one of those things that you don’t know until you know. With costs getting a lot closer for dual/combined vs single nowadays I think it’s becoming a no brainer

If the cost is the same, absolutely, I’d prefer a dual-sided. Personally, I “regret” spending the extra $300 for my dual-sided PM, but as I said, in my n=1 case, the only good I’ve gotten out of it is to know that I don’t need a dual-sided power meter. There are certainly cases mentioned above where it makes some sense and might provide actionable info.

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