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Left / Right Power - How do you use it?

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Left / Right Power - How do you use it?

Old 12-30-20, 07:42 PM
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Zaskar
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Left / Right Power - How do you use it?

I'm one ride into L/R power data. I've had a power meter for years, but I'm new to the L/R data. I rode for an hour today. It was a Zwift ride, which was good... 'cause I was looking down a lot ;-)

Early in, I noticed I was in the 52/48 - 55/45 range if I wasn't paying attention. I guess I'd attribute that to a hamstring tear a few years ago on the /R side. But I kept forcing myself to pedal smoothly, even thinking about the effort of the right leg. When I thought about it, I was 50/50. Toward the end of the ride, I was holding 50/50 - like, I'd sorta forget about the power as I paid more attention to what was going on in Zwift. I finished with 50/50. BUT - I'm certain, I'd have been more like 52/48 (or worse) had I not been "notified" that I'm not naturally/automatically even.

Full disclosure - I'm 52, been riding 47 years, raced since I was 12... road bike, gravel, mtb. So, I'm not new to pedaling... and may have some habits to break

I do NOT plan on watching that L/R data field during outside rides. I hope I'll see that it stabilizes at 50/50 or 49/51.

How are you guys using the L/R data? When, if ever, would you add one-leg drills?
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Old 12-30-20, 08:08 PM
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Originally Posted by Zaskar View Post
I'm 52, been riding 47 years, raced since I was 12 [...] When, if ever, would you add one-leg drills?
So, during those decades have you been able to attain your riding goals? Have you been experiencing systematic pain or discomfort on one side and one side only?
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Old 12-30-20, 08:15 PM
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I'm curious what happens to L/R balance when you're at the end of a hard interval that you're having trouble completing? My suspicion is your L/R balance will not be the limiting factor. If one leg starts to hurt more than the other you would likely subconsciously adust and push harder with the other leg.
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Old 12-30-20, 08:21 PM
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I shattered my left leg in a bad skiing accident years ago and still have lots of metal and screws inside along with a foot long skin graft (compartment syndrome) so my left leg is a bit weaker than my right. My main use for the dual power is to improve the use of my left leg. It's been several years since I started doing this but honestly, while my leg has definitely become stronger, it doesn't seem to make any difference when I'm not focusing on it as my power is almost always 53/47 or 52/48.

But, it does give me something to focus on when I'm working on my left leg....
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Old 12-30-20, 08:26 PM
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For most people, Left and right data is a solution looking for an issue.
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Old 12-30-20, 08:33 PM
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For me, just tooling around, there may be a couple of percent difference left to right. Working hard, the difference is typically a tenth of a percent, way below the margin of error of the power meter.

So, for me, and I think most people, it’s essentially worthless.
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Old 12-30-20, 08:36 PM
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Originally Posted by Zaskar View Post

How are you guys using the L/R data?
I don't.

Originally Posted by Zaskar View Post
When, if ever, would you add one-leg drills?
Never, unless you're planning on having a pedal or crank arm fall off one day and want to be prepared for riding home one-legged.
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Old 12-30-20, 08:52 PM
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Originally Posted by rubiksoval View Post
I don’t.
Then why are you in this thread?

Last edited by Trsnrtr; 12-31-20 at 08:03 AM. Reason: fixed quote tag
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Old 12-30-20, 08:56 PM
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Originally Posted by Zaskar View Post

Then why are you in this thread?
Same reason I go to any thread. To read and potentially respond.

Hence, discussion board.

If you only want people that use L/R data to respond, you're not going to have many, if any, responses. As noted by the responses above.
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Old 12-30-20, 10:16 PM
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The cool kids know that it's all about L+R not L vs R.
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Old 12-30-20, 11:12 PM
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I used it recovering from a foot injury. Outside that scope it's a distraction and not helpful. Neither are single leg drills in my experience.
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Old 12-30-20, 11:38 PM
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Many people shell out for 2 sided pedal PMs because they are convinced that they are very imbalanced (because one leg really *feels* stronger) and that one-sided would not be accurate for them. then they find out that they are pretty close to 50/50 after all, and they didn't need two sided.

Ask me how I know.
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Old 12-31-20, 06:47 AM
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Originally Posted by MinnMan View Post
Many people shell out for 2 sided pedal PMs because they are convinced that they are very imbalanced (because one leg really *feels* stronger) and that one-sided would not be accurate for them. then they find out that they are pretty close to 50/50 after all, and they didn't need two sided.

Ask me how I know.
How do you know?
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Old 12-31-20, 07:35 AM
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I've used L/R balance as an aid during recovery from a bad injury.
I also use it to detect when I'm beginning to fatigue, my balance shifts when I'm overtraining.
I'm typically 51/49, 50/50 or 49/51. When I get fatigued it can go to 55/45 without me feeling it.

I also find that in low power output, (especially on Zwift) balance can range from 35/65 to 65/35, but once the effort goes up my balance gets close to 50/50.

I have a set of Favero Assioma Duo's and also a left-only PM
After realizing that balance can easily be 48/52 or 52/48, single sided PM's have a fairly wide range of inaccuracy due to the doubling effect.

In most instances this doesn't really matter, but in training at specific numbers it could.
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Old 12-31-20, 08:09 AM
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That hamstring injury (and an odd heel wiggle on the same leg) had my curiosity up - wondering if there was an imbalance and how bad it might be. I was glad to see it wasn't significant.

I needed a crank and wanted (another) power meter, so the Shimano/Stages L/R crank fit the bill. The 3-sec and average L/R data fields will not be visible on rides... that would suck the fun out of any ride.

And yeah - I know I don't "need" a L/R power meter. I also don't "need" a power meter... or carbon bars, carbon seat post, carbon frame, carbon wheels, five bikes, etc. I think most of us left "need" behind a long time ago.
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Old 12-31-20, 08:24 AM
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Originally Posted by Zaskar View Post
That hamstring injury (and an odd heel wiggle on the same leg) had my curiosity up - wondering if there was an imbalance and how bad it might be. I was glad to see it wasn't significant.

I needed a crank and wanted (another) power meter, so the Shimano/Stages L/R crank fit the bill. The 3-sec and average L/R data fields will not be visible on rides... that would suck the fun out of any ride.

And yeah - I know I don't "need" a L/R power meter. I also don't "need" a power meter... or carbon bars, carbon seat post, carbon frame, carbon wheels, five bikes, etc. I think most of us left "need" behind a long time ago.
I had my Assioma Duo's long before my recent injury, but I found the balance numbers very helpful during my recovery from my recent injury, where I had significant muscle tears on my right side.
Out on the road? I don't use balance, but will look at average balance after a ride, especially if I felt fatigued.



Need?
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Old 12-31-20, 08:48 AM
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Originally Posted by colnago62 View Post
For most people, Left and right data is a solution looking for an issue.
Correct. More data to confuse us, granted there are those like the above who could benefit knowing how their damaged leg is performing. It seems like the flood of data we get from our devices is overwhelming! I find power and cadence critical for my Sufferfest sessions but once on the road power becomes less important, mostly because to religiously use it means having too close a relationship with my Wahoo Bolt. I enjoy the scenery too much and like my attention focused on traffic. One question I have though is whether on a ride like the Garrett County Gran Fondo Diabolical Double 125 miles 16,500 the more important metric is power or HR? I know over the span of the ride my average HR goes down as I fatigue, so it is a bit of a moving target. I can use FTP as a gauge but think that FTP at 40 miles may be more sustainable than FTP at 100 miles...
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Old 12-31-20, 09:06 AM
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Originally Posted by waters60 View Post
Correct. More data to confuse us, granted there are those like the above who could benefit knowing how their damaged leg is performing. It seems like the flood of data we get from our devices is overwhelming! I find power and cadence critical for my Sufferfest sessions but once on the road power becomes less important, mostly because to religiously use it means having too close a relationship with my Wahoo Bolt. I enjoy the scenery too much and like my attention focused on traffic. One question I have though is whether on a ride like the Garrett County Gran Fondo Diabolical Double 125 miles 16,500 the more important metric is power or HR? I know over the span of the ride my average HR goes down as I fatigue, so it is a bit of a moving target. I can use FTP as a gauge but think that FTP at 40 miles may be more sustainable than FTP at 100 miles...
In your Gran Fondo scenario, using Power or HR is not about keeping working at FTP, its about not burning matches. A ride like that, Id be using power to keep my effort below FTP for climbs early in the ride, saving matches for late in the day.

Given the variabilities of HR, power is going to be a more effective tool for doing that
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Old 12-31-20, 10:08 AM
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Typically it is just more accurate than doubling a single side. If you arent physically in a horrible state, nothing to do. If you have a good bike fit any leg length issues should already be accounted for anyway.

I just prefer the accuracy of a Quarq to do aero testing. I could care less about leg imbalance.
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Old 12-31-20, 01:09 PM
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Originally Posted by MinnMan View Post
Many people shell out for 2 sided pedal PMs because they are convinced that they are very imbalanced (because one leg really *feels* stronger) and that one-sided would not be accurate for them. then they find out that they are pretty close to 50/50 after all, and they didn't need two sided.

Ask me how I know.
I think most people are pretty close to 50/50 especially during harder efforts like the intervals most people buy power meters to titrate. And, as @RChung likes to say, training just isn't that sensitive.

A left only meter can do +/- 1.5% accuracy for your left leg, but it's +/- some unknown % for total power. That's close enough for training and dieting, not close enough for aero testing, and subjectively not a good value for some people.
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Old 12-31-20, 01:59 PM
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I used it to adjust for a leg length difference. In my case they differed about 6% at low effort and 10% at higher effort. Now they're close to parity at easy efforts while if I push harder they diverge 4-5% or so. If I go all out they're back at parity, and always were close to, oddly enough. So the leg length disparity is a little undercorrected with 3mm of shims, but that's fine. Interesting also is the dynamics, which is where in the pedal stroke you make power and will tell you all kinds of things about your bike fit - if you move your seating position forward, as an example, the stroke will rotate clockwise. If your saddle position is too high, the peak power section will shrink. If like me you have a leg length disparity then the shorter leg will have a shorter stroke section with a shorter peak stroke. This also lets you dial in your seat height perfectly, by the numbers. (Comfort is a poor indicator here as we tend to be comfortable in our bad habits.) Of course, once you have it nailed there's not much need for the dynamics IMO, unless you really want to squeeze out the last fraction of performance possible - but I don't, since there's nothing in it for me other than being out enjoying the sun and fresh air, and the feeling of working.
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Old 12-31-20, 04:08 PM
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Vectors also report "platform center offset" and that was pretty useful, but again because of an injury and non standard biomechanics. I supinate a lot and have been dealing with tendonitis on the outside bottom of my foot. The Vectors show clearly that I supinate on the bike too. That was useful to show my podiatrist, in terms of load management for the tendon. Also useful in terms of fit, but again because of my particular issue.

I bought dual sided Vectors (1) because I have a Cervelo with its own BB standard so I thought pedals would be more transferrable if I ever change bikes, and (2) I wasn't willing to pay what the L only version cost and still not know my power output. Not that it isn't good enough for training, that just struck me as a bad value. Now I'm glad I have them.
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Old 01-01-21, 10:16 AM
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I have several different power meters on different bikes - road, time trial, track (pursuit and sprint) and tandem. May preferred PM is SRM which I have on my road bike and I have Garmin Vector 3 that I move around on different bikes and my head unit is a Garmin 830.

Vector 3 two sided and the Garmin 830 generate a lot of interesting data and graphs from left right balance to pedal smoothness. I have not determined any uses for the extra data to improve performance. For example, what is the optimum pedal smoothness and if I am not smooth enough, how do I improve? I am not going to say it is meaningless or useless but I cannot make any of it operational for a competitive advantage.

I do not do one leg pedaling drills although if I am using a coach who puts them into a routine, I will do them to make him happy - no downside.
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Old 01-01-21, 10:35 AM
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Originally Posted by gregf83 View Post
I'm curious what happens to L/R balance when you're at the end of a hard interval that you're having trouble completing? My suspicion is your L/R balance will not be the limiting factor. If one leg starts to hurt more than the other you would likely subconsciously adust and push harder with the other leg.
From time to time, I am at the track in Carson, CA and Team USA Paralympic is training. I walk into the track and see a racer on the track going really fast and then realize he only had one leg. It seems that all the blood oxygen that is available goes to the remaining leg and we know it does not take much strength to make a lot of power.

Even more amazing are the guys with one arm that do a standing start out of the starting gate and look fast. Try starting a bike in a big gear with one arm and then drop to the aerobars. Or better yet, do not try that at home.

On Fiesta Island, I see Team USA para members training. I was on my TT bike at 25 mph and there was a Team USA guy ahead on a hand cycle. He was doing maybe 24 mph because when I passed him it took some time. Once again, all the blood oxygen and heart rate are available to the arms for power generation. It is matter of training and getting enough strength to make the power.

My take away is the differences in left and right leg strength capability do not matter for power generation since blood flow / oxygen will be channeled to the stronger or less fatigues leg or arm. Accuracy of power measurement is a different matter.
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Old 01-01-21, 11:29 AM
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Originally Posted by Hermes View Post
From time to time, I am at the track in Carson, CA and Team USA Paralympic is training. I walk into the track and see a racer on the track going really fast and then realize he only had one leg. It seems that all the blood oxygen that is available goes to the remaining leg and we know it does not take much strength to make a lot of power.

Even more amazing are the guys with one arm that do a standing start out of the starting gate and look fast. Try starting a bike in a big gear with one arm and then drop to the aerobars. Or better yet, do not try that at home.

On Fiesta Island, I see Team USA para members training. I was on my TT bike at 25 mph and there was a Team USA guy ahead on a hand cycle. He was doing maybe 24 mph because when I passed him it took some time. Once again, all the blood oxygen and heart rate are available to the arms for power generation. It is matter of training and getting enough strength to make the power.

My take away is the differences in left and right leg strength capability do not matter for power generation since blood flow / oxygen will be channeled to the stronger or less fatigues leg or arm. Accuracy of power measurement is a different matter.
I've spoken before about my friend, a cycling coach, who had years of power data before a crash that eventually led to the amputation of one leg above the knee. It took a couple of years of arduous training but eventually he matched and then exceeded his pre-amputation FTP. He doesn't worry about L/R asymmetry. He can't "pedal circles" or "pull up" or "scrape the bottom of the pedal stroke." If he tried, he'd yank the prosthetic off his stump. All he can do is stomp with his prosthetic, so he stomps down hard, and all he pays attention to is total power, not separate L/R power.
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