The downside to single-sided crank-based power meters....
Discussion
I'm quite good friends with my bike fitter, and, being a chiropractor, I am quite fascinated by the science in bike fitting. I know I have a mild scoliosis and a slight pelvic tilt on the left, which means my left leg generally extends a little further than the right....so if my saddle is marginally too high, it's always my left calves/hamstrings or ITB that notice it the most.
My power2max power meter reports a 46/54 L/R split on most of my rides, give or take. This could lead you to believing my left quads are quite weak.
However, today I tried on some electromyography shorts which measure the balance between L/R quads and hamstrings. The overall L/R balance was indeed 46/54.....but in actual fact it was the LEFT side that was more dominant. I think you can see where this is going....
The balance between my left and right quads was, give or take, pretty equal....but my left hamstring was FAR more active than my right....I was approx 25% L and R quads, and about 30% L hamstring and only 20% R hamstring...so that L hamstring is working twice as hard as the right!!
The power2max power meter has been assuming that my left leg pulling up (ie hamstring activation) has been my right quad pushing down (hence it got the right 46/54 split....but just the wrong way around!
Fascinating stuff, at least I thought so
We've put a 3mm shim under my left cleat to prevent the left side from extending quite so far and, whilst it didn't completely even out the difference, it did appear to make that difference a little less....so I'm going to trial it for a couple of weeks and see how I get on!
No idea why I'm sharing this with you... just in case anyone is interested
My power2max power meter reports a 46/54 L/R split on most of my rides, give or take. This could lead you to believing my left quads are quite weak.
However, today I tried on some electromyography shorts which measure the balance between L/R quads and hamstrings. The overall L/R balance was indeed 46/54.....but in actual fact it was the LEFT side that was more dominant. I think you can see where this is going....
The balance between my left and right quads was, give or take, pretty equal....but my left hamstring was FAR more active than my right....I was approx 25% L and R quads, and about 30% L hamstring and only 20% R hamstring...so that L hamstring is working twice as hard as the right!!
The power2max power meter has been assuming that my left leg pulling up (ie hamstring activation) has been my right quad pushing down (hence it got the right 46/54 split....but just the wrong way around!
Fascinating stuff, at least I thought so
We've put a 3mm shim under my left cleat to prevent the left side from extending quite so far and, whilst it didn't completely even out the difference, it did appear to make that difference a little less....so I'm going to trial it for a couple of weeks and see how I get on!
No idea why I'm sharing this with you... just in case anyone is interested
Well there website says this (I don't know much about there product).
Left-right balance
Your power2max power meter estimates the contribution of your left and right leg as your ride. This offers useful additional information for your training.
Note: Power right = downward pressure on the right plus upward pull on the left. Power left = downward pressure on the left and upward pull on the right.
Does this means its single sided? Surely you down right/up left can change as can down left /up right? Therefore difficult to say which leg is more dominant (unless you assume exertion / performance is linear for all muscle groups and neither fatigue quicker than others).
As per my comment on the other thread, my legs vary between 49:51 to 51:49 but are pretty consistent at 50:50 when using probably up to 95% FTP, big efforts and the difference does increase.
Those shorts sound interesting!
Left-right balance
Your power2max power meter estimates the contribution of your left and right leg as your ride. This offers useful additional information for your training.
Note: Power right = downward pressure on the right plus upward pull on the left. Power left = downward pressure on the left and upward pull on the right.
Does this means its single sided? Surely you down right/up left can change as can down left /up right? Therefore difficult to say which leg is more dominant (unless you assume exertion / performance is linear for all muscle groups and neither fatigue quicker than others).
As per my comment on the other thread, my legs vary between 49:51 to 51:49 but are pretty consistent at 50:50 when using probably up to 95% FTP, big efforts and the difference does increase.
Those shorts sound interesting!
ALawson said:
Well there website says this (I don't know much about there product).
Left-right balance
Your power2max power meter estimates the contribution of your left and right leg as your ride. This offers useful additional information for your training.
Note: Power right = downward pressure on the right plus upward pull on the left. Power left = downward pressure on the left and upward pull on the right.
Does this means its single sided? Surely you down right/up left can change as can down left /up right? Therefore difficult to say which leg is more dominant (unless you assume exertion / performance is linear for all muscle groups and neither fatigue quicker than others).
As per my comment on the other thread, my legs vary between 49:51 to 51:49 but are pretty consistent at 50:50 when using probably up to 95% FTP, big efforts and the difference does increase.
Those shorts sound interesting!
Ah right....but the fact it estimates left-side pulling up as right-side power can lead one to believe your right quad is more dominant, whereas it's actually my hamstrings on my left side!Left-right balance
Your power2max power meter estimates the contribution of your left and right leg as your ride. This offers useful additional information for your training.
Note: Power right = downward pressure on the right plus upward pull on the left. Power left = downward pressure on the left and upward pull on the right.
Does this means its single sided? Surely you down right/up left can change as can down left /up right? Therefore difficult to say which leg is more dominant (unless you assume exertion / performance is linear for all muscle groups and neither fatigue quicker than others).
As per my comment on the other thread, my legs vary between 49:51 to 51:49 but are pretty consistent at 50:50 when using probably up to 95% FTP, big efforts and the difference does increase.
Those shorts sound interesting!
To be a complete pedant, its only the LR balance that's estimated It still measures (rather than estimates) total power - it doesn't see or care how that's generated, it's just torque between the spider and the rings. It just defines 180deg as left and 180deg as right somewhat arbitrarily to give you a balance figure. (unlike a single sided power meter that takes left and doubles) - interesting thought experiment what those balance changes would do to your total power if you had (say) stages..
FWIW I found my reported balance is a lot more even with a quarq than with the vectors it replaced. Proabably a similar scenario; I have a shorter left leg, but shimming it gave me problems at the top of the stroke on the TT - from which I conclude the length difference is in the femur - with shims my knee was pushed too high. Mostly I just don't worry about it all and try to pedal harder
It still measures (rather than estimates) total power - it doesn't see or care how that's generated, it's just torque between the spider and the rings. It just defines 180deg as left and 180deg as right somewhat arbitrarily to give you a balance figure. (unlike a single sided power meter that takes left and doubles) - interesting thought experiment what those balance changes would do to your total power if you had (say) stages..FWIW I found my reported balance is a lot more even with a quarq than with the vectors it replaced. Proabably a similar scenario; I have a shorter left leg, but shimming it gave me problems at the top of the stroke on the TT - from which I conclude the length difference is in the femur - with shims my knee was pushed too high. Mostly I just don't worry about it all and try to pedal harder
Well, it's nice to know it's doing a VERY good job of estimating....it got the 54/46 split spot on.
I'm going to try the shims and see what happens. I did lower my saddle height because this caused some minor calf or itb discomfort due to being over-stretched....now the shim is in, I may raise it up 1-2mm
I'm going to try the shims and see what happens. I did lower my saddle height because this caused some minor calf or itb discomfort due to being over-stretched....now the shim is in, I may raise it up 1-2mm
mikecassie said:
No idea about my individual leg lengths but my Quarq PM shows a more even L/R balance than my P2M PM. P2M is often around 45/46%L to 55/54%R, Quarq is more often 48%L to 52%R.
I just reckon it's within the tolerance of the PM's.
Well based on the electromyography shorts, there definitely is a leg power difference...and it's basically all in my hamstrings!! They're soon looking at ones which also do your glutes, hip flexors and calves which will also be quite fascinating!I just reckon it's within the tolerance of the PM's.
I have raised my saddle up by 1-2mm and I'll see how that goes tomorrow. I found that when it was 2-3mm higher after a while I developed a mild ITB issue and also a calf which felt it was being stretched just a tiny bit too much, but the right leg felt perfect....so by adding 3mm of shim, I should (in theory) be able to raise the saddle up a notch (so the right leg will be as it was) and the left leg will be as if the saddle was a few mm lower.... It's something that if I don't notice anything immediately (in terms of any discomfort) then I'll have to monitor over 2-3 weeks....if still no issues, then I think I'll be fine
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