Pedal based Power Monitoring Systems

A light bike doesn't replace good fitness.

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amaferanga
Posts: 20
Joined: Wed Oct 06, 2010 8:52 am
Location: Sheffield, United Kingdom
Rick wrote:
Here is EXACTLY how balancing power out put can increase power output:
1 leg - 50%
If I now start using the other leg: 100%
That is a 100% increase !

I know that is overly simplistic; but so are the arguments that it makes NO difference.

It's not simplistic. It's stupid and meaningless

devinci
Posts: 3039
Joined: Sat Jan 03, 2009 9:43 pm
Location: Canada
the thing is more: it WONT be 70/30 and most likely not 60/40 either.

What matters most is the power output and the end of the line, with both legs. Its not like having independant legs measurement will help you get to 50/51%....

rchung
Posts: 97
Joined: Sat Jul 09, 2011 5:01 am
Rick wrote:What if it is 60/40 ?
70/30 ?
85/15 ?

At some point, I think any rational person would "care".
Otherwise, I go back to my original question: Why bother to use both legs at all ? Why not just use one crank arm ? Think of the increase in power/weight ratio !

Here is EXACTLY how balancing power out put can increase power output:
1 leg - 50%
If I now start using the other leg: 100%
That is a 100% increase !

Studies of single-leg amputees suggest that way more than 50% of total pre-amputation power can be produced even with large bilateral asymmetry; see, for example, this study where a transfemoral amputee was doing TT's at an average power of 4.5 watts/kg. That's probably down from his pre-amputation power but I'm guessing it's not 50% down -- he would have had to have been producing 9 watts/kg for that. Alex Simmons has had a transfemoral amputation and he recently surpassed his pre-amputation power over longer durations (his sprint has suffered a lot, though). The bottom line is that (except for sprinting) we're more limited by our aerobic capacity than the ability to put high force or balanced force into the pedals. Focus on power output. There is no evidence that "balanced" production increases power output over slightly unbalanced production --though if you amputate one of the legs, maybe, since that's hardly "slightly unbalanced".

Rick
Posts: 2021
Joined: Sat Aug 29, 2009 4:30 pm
It's not simplistic. It's stupid and meaningless

You probably won't want to buy one.

Rick
Posts: 2021
Joined: Sat Aug 29, 2009 4:30 pm
There is no evidence that "balanced" production increases power output over slightly unbalanced production --though if you amputate one of the legs, maybe, since that's hardly "slightly unbalanced".

There is no evidence.
OK. How many studies have been performed on slightly unbalanced riders ?

How unbalanced must it be to be considered "more than slightly unbalanced" ?

Could it be that there is very little data because there are so few power meters that measure the difference ? hmmmm......

I really find it amusing that people are arguing that they don't need to know how efficient half your body's power transfer apparatus is working. If you don't care....don't buy the product. I don't care about the difference between "Grade 3 ceramic balls" and "Grade 5 ceramic balls"....but I don't really find in necessary to tell people who think it makes a difference they are wrong. I certainly wouldn't bother to argue that measuring the difference in drag between Grade 3 balls and Grade 5 balls was "stupid and meaningless" (even though I suspect it is)

rchung
Posts: 97
Joined: Sat Jul 09, 2011 5:01 am
Rick wrote:
There is no evidence that "balanced" production increases power output over slightly unbalanced production --though if you amputate one of the legs, maybe, since that's hardly "slightly unbalanced".

There is no evidence.
OK. How many studies have been performed on slightly unbalanced riders ?

How unbalanced must it be to be considered "more than slightly unbalanced" ?

Could it be that there is very little data because there are so few power meters that measure the difference ? hmmmm......

I really find it amusing that people are arguing that they don't need to know how efficient half your body's power transfer apparatus is working.

1. Force sensing pedals have been around for a while. For examples, see many of the studies where S. Kautz is one of the co-authors.

2. The amputee study I linked above shows that even with huge bilateral asymmetry, his power was almost certainly affected by less than 25%; that is, he was measured post-amputation at 4.5 W/kg for a TT. Unless his pre-amputation W/kg was *greater than* 6 W/kg, it means he could produce *at minimum* 75% of his prior power with only one leg. And, we could well expect his pre-amputation W/kg to be probably less than 6 W/kg since his VO2Max was 63 ml/kg/min. In other contexts, such as the Kautz data above, we know that "evenness" of the application of force around the crank cycle is *not* related to power output. And, from other studies, we know that aerobic power output is the main determinant of TT performance. All of this together is just more evidence that small imbalances ("small" meaning something that you wouldn't have noticed if you hadn't measured it) are not the limiter in performance. The muscles in one leg are not quite but almost up to the task of producing as much power from aerobic metabolism as two legs, so unless your imbalance were something like 75/25 or greater (and you would have noticed something of that magnitude), you'll be able to compensate for it. If not, amputees would have a lower respiration rate than people with two legs.

Squint
Posts: 240
Joined: Mon Oct 10, 2005 9:23 pm
Surely there is a TdF champion inside me if I could only develop an efficient pedal stroke and achieve perfectly equal leg strength in both legs?

After all, that's how the pros got fast, right? It couldn't be from youth, good genetics, smart training and hard work. Anything but hard work...I want a quick and easy solution.

Tapeworm
Posts: 2585
Joined: Thu May 03, 2007 10:39 am
Well my good man, get thee to some Powercranks with Pedal based power meters and when you have a 50/50 power split and power through 360 degrees of the pedal stroke just watch the pro-like power be unleashed.
"Physiology is all just propaganda and lies... all waiting to be disproven by the next study."
"I'm not a real doctor; But I am a real worm; I am an actual worm." - TMBG

Squint
Posts: 240
Joined: Mon Oct 10, 2005 9:23 pm
I almost forgot the paleo diet, Crossfit, and yoga. Anything but riding a bike...

Rick
Posts: 2021
Joined: Sat Aug 29, 2009 4:30 pm
....and I am ditching my left crank arm completely! There goes another 150 gms! Who knew it wasn't helping my power output. Thanks !

I have a Left Specialized S-Works road shoe in size 42.5 that I won't be using. PM me if you are interested.

Next question:
Could I be a little bit more aero if I saw off the left half of my handlebars ? That can't possibly affect power output, can it ?

Tapeworm
Posts: 2585
Joined: Thu May 03, 2007 10:39 am
You'd also only need one pedal based power meter which will tell you where your power coming from 100%.
"Physiology is all just propaganda and lies... all waiting to be disproven by the next study."
"I'm not a real doctor; But I am a real worm; I am an actual worm." - TMBG

Murphs
Posts: 1117
Joined: Thu Feb 05, 2009 12:04 am
Location: Gold Coast, QLD, Australia
Rick wrote:....and I am ditching my left crank arm completely! There goes another 150 gms! Who knew it wasn't helping my power output. Thanks !

I have a Left Specialized S-Works road shoe in size 42.5 that I won't be using. PM me if you are interested.

Next question:
Could I be a little bit more aero if I saw off the left half of my handlebars ? That can't possibly affect power output, can it ?

You've only got half a brain, so doing the rest makes sense

devinci
Posts: 3039
Joined: Sat Jan 03, 2009 9:43 pm
Location: Canada
Well this thread is about pedal based power meter. Not only L-R balance and power distribution. Looks like Rick is sold to the pedal based system, thats cool. But I think you must think twice before buying such a device for 2 reasons:

1- if you race, and crash, your pedals will most likely take a beating.

2- the system has proven nothing yet. No longevity test, no awfull weather condition test, etc.

Thats why I'd favor something proven strong.

Butcher
Shop Owner
Posts: 837
Joined: Sun Jan 03, 2010 4:58 am
Consumers are the best testers but I would think that Garmin would have some type of testing esp. with foul weather. Longevity is hard to prove. By the time you know your pedal [or anything else you make] lasts a long time, it would be outdated. Good engineering and build quality is a sound way to start with the longevity issue you mention.

I understand you may want to wait for other consumers to see if it works but someone has to buy the first one.

nathanong87
Resident master of GIF
Posts: 3183
Joined: Mon Jul 18, 2011 2:44 am
Contact:
this might be completely hearsay, but i've heard that look isn't the one making the pedals? some outsourced "china" look pedal company? i dunno. if i'm wrong i'm sure someone will correct me.

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