Pedal Balance
I've been using my new PowerTap P1 pedals for a month now on the trainer. I usually see a 53/47 L/R wattage balance when I review a ride afterwards. That ratio seems to hold pretty much during all types of intervals: warm-up, short VO2 work, longer FTPs, and steady state. The pedals work fine measuring left only and right only (meaning I see 100/0 and 0/100) when I do single leg drills. So now I'm left with pondering (a) why the imbalance and (b) what - if anything- to do about it.
At first, I made the simplistic assumption: "Well, my left leg is stronger than my right." But this seemed at odds with a few other observations:
- When doing single leg knee bends, my right seems both more stable and stronger
- When skiing, it is easier to make left turns (which utilize the right leg to the greater extent) than right turns.
- I currently am re-habbing a left hamstring and piriformis situation, and am definitely favoring my left leg.
So I dug into, and learned a bit about pedaling balance. The biggest problem people seem to have is that one leg gets in the way of the other. Meaning: if I am not sufficiently "unweighting" my foot during the pedal upstroke (6-to-12 o'clock), then the opposite (contralateral) leg will have to work harder during its 12-to-6 portion. So: if my right leg is floating up while my left is pushing down, the left will have to work harder to maintain cadence, causing the imbalance noted above.
Next step: see if this theory is correct. First off, when doing single leg drills, it does feel as if I "chain-slip" sooner and more often on the right than the left. That is, after about 15-20 seconds of a right-only drill, there starts to be a slack in the pedaling between about 10 and 12, sufficient to cause an audible sound of the chainring losing, then re-gaining its grip on the chain. Next, I discovered that PowerTap has an App which shows, in real time, a graphic representation of watts applied at the various reporting stations around the clock on each pedal. (When I used a CompuTrainer from 2007-2014, I had access to a similar metric, but never paid it any attention - just too hard to use, for me.)
My left was indeed generating more power than my right, but it sure didn't feel like it, unless I actually took my foot off the pedal and could see a "zero" on that side. So I'm wondering if the pedals are not sufficiently accurate to use for improving/smoothing my stroke. At this point, I will simply start by following the old Quality Improvement maxim: "You only improve what you measure", and take about 5 or 10 minutes at the end of every indoor session to look at the numbers when I'm cooling down. And continue searching for ways to confirm or refute whether I have an imbalance; if that imbalance is important; and what to do about it if it is.
Comments
I know I'm imbalanced overall -- years of starboard rowing has given the left side of my body more flexibility and range of motion, whereas my right side is a bit crimped. Once my fitter realized this, my bike fits have changed to favor my right side (where I ended up developing all the aches and pains and injuries). I no longer have pains on the right side of my body (mainly lower back pain and hand numbness), but I wonder if my fit has something to do with it.
I'll be following your search for insight. It may be "just one of those things" ... or it may be something that can be corrected, but does it matter if you're balanced? And what is "balanced"? Certainly 90/10 isn't, but a +/- 5w differential might be. I think it might be useful to get L/R numbers from other people to see if you're an imbalanced outlier, or if everyone has some degree of imbalance.
Nice thread.
In my case, one leg is about 1/4 inch or so short than the other. Effects both my bike and run efficiency.
Is the idea that a perfect effort from both legs would yield more watts under the same effort and conditions? I am not sure that would necessarily be the case, however logically it seems the more balanced you drive the watts from each leg the more efficient you would become.....Not sure if small differences between the two legs would be worth the time and effort to correct but certainly large discrepancies between the two legs in terms of watts generated should be noted, understood and focused on in my view.
SS
It hasn't been on the top of my list to fix.
One of the very interesting things I've noted is when you look at the files posted by pro riders almost all are 50.0/50.0 or very close to that.
Last year's TdF ride: http://home.trainingpeaks.com/public/workout/76ZQVZ3CN3X3S2FGK2AQW6A7FE
That is interesting. I wonder if they are naturally balanced, which makes them pros rather than mere mortals (like good genes, flippers for feet, etc.), OR if it's something to be worked on after you've made all the other gains you can -- marginal returns that matter at the pointiest end.
Yeah, I started looking into that stuff from Hunter Allen when I first discovered my discrepancy. I first had to learn the language..."Power released" basically means power generated on the downstroke, and "Power absorbed" references how the leg is doing on the upstroke. With that in mind, I found that my Power Released was exactly the same L/R, and Power Absorbed was over 25% higher on the right than left. As I interpret it, that means my right foot is "heavier", i.e., not unweighting as much as the left is. And basically, a lot of the effort on the left is being "wasted" just pushing my right leg back back up on its (the right's) downstroke. So when I do drills, I should try and concentrate not on working my right leg harder, but on lifting it more on the upstroke, but SMOOTHLY.
There are other data I can look at, such as "Torque Effectiveness" and "Smoothness", but I have yet to learn what THEY mean, so I think I'll just work on one thing at a time, not overload either my brain or my legs.
Another interesting thing I've noticed with these power files is that triathletes have a lot to learn. Look at one of the fastest Ironmen out there. http://home.trainingpeaks.com/athlete/workout/YOYYRQ5AQ4BYLPNLFKJB6UTV64
Full article here: https://home.trainingpeaks.com/blog/article/power-analysis-how-lionel-sanders-broke-the-ironman-world-record
His power balance is awful. He could probably use a week with some pro cyclists working on that for even more gains. I think as you get better and better the marginal gains get really hard to find. If pro triathletes hired or consulted with TdF type cycling coaches, they would get better at things like bike handling skills, power balance and other "soft" things.
Me, I'm still working on FTP
I think they ended up in the triathlon equipment trash bin together with alot of the other gadgets triathletes buy looking for an Edge
I have read and been told by other riders that you can feel that you are achieving balance when your pedal stroke feels like it is at the same speed through each full rotation and that you feel like you are making circles with instead of only pushing down on the pedals.
Finally, I notice that during FTP tests, that when I pedal at a higher cadence - in the 100 area, it becomes difficult to mash the pedals, and you are forced to have a smoother stroke across the full 360 degrees. I have a hub-based power tap as well as a wahoo kickr, neither of which measures L/R balance. However, I was at 49/51 at my last bike fitting, which my fitter deemed to be close enough to being balanced for a weekend warrior.
My observation from having used Powercranks briefly back in the Dark Ages and speaking with coaches and athlete who used them is:
- Our legs and big leg muscles are designed to apply the most power to the act of pushing against something -- the earth when running or jumping, or pedals when cycling.
- Applying power in a true 360 means recruiting the hip flexors, a relatively small muscle. Athletes who used PC's found that the hip flexor became quickly thrashed and the body compensated by applying less power on the downstroke. There would be an extensive adaptive phase, as the hip flexor was better conditioned, but at the expense of quality training to improve power on the downstroke.
Note that we added Spinups and One Legged Drills to the OS plans this year. The intent of this is largely to increase your "pedal awareness" across the arch of your pedal stroke. Where and how am I applying power across the 360 arch? My pedaling technique cues across this arch are:In the end, this is about increasing my awareness of what I'm doing and when in the pedal stroke, so I can choose to use more hamstring here, less quad there, etc. However, the key to all of this is that nothing is free. If you find yourself putting out more watts because you're more aware of the clock face, those watts aren't free. You're still doing the (more) work and ability to sustain that higher workload is a fitness issue.