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Powertap P1 Question
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blayze
Oct 1, 18 19:50
Post #1 of 9 (1023 views)
I recently completed a 70.3 where I sustained a left glute injury 5k into the 90k ride. I labored through the bike and managed to finish the race and have since reviewed the bike data.

The power was about 30% lower than what I typically race at, which was expected. However, I was shocked to find that the L/R pedal balance was 48 (L) / 52 (R)! Given the injury was to my left glute I had expected the imbalance to be significantly greater in favor of the right, which (at least in my head) felt like it was doing more of the work. So the question is... if garmin is reporting the L/R data for both pedals... then does mean they must both be functioning properly? I know it's a weird question to ask... I'm just paranoid now because it feels impossible that my balance could have been THAT close to even given the injury!

Thanks
Last edited by: blayze: Oct 1, 18 20:44
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Re: Powertap P1 Question [blayze] [ In reply to ]
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JRC
Oct 2, 18 0:34
Post #2 of 9 (955 views)
I'm not that suprised,

I think in a lot of cases if one leg is down you will automatically scale power of both legs, as your body is used to outputing the same to both, it would probably take a fair amount of time ( weeks, months?) to reprogram yourself.
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Re: Powertap P1 Question [blayze] [ In reply to ]
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exxxviii
Oct 2, 18 5:00
Post #3 of 9 (869 views)
What is your typical L/R balance on a healthy ride? For example, if you were usually 52/48, then that would be a pretty healthy swing.
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Re: Powertap P1 Question [blayze] [ In reply to ]
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nickwhite
Oct 2, 18 5:24
Post #4 of 9 (846 views)
Quote:
However, I was shocked to find that the L/R pedal balance was 48 (L) / 52 (R)!

Some power meters report power balance drastically wrong. I wouldn't trust this until I did some more testing.
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Re: Powertap P1 Question [exxxviii] [ In reply to ]
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blayze
Oct 2, 18 6:56
Post #5 of 9 (802 views)
exxxviii wrote:
What is your typical L/R balance on a healthy ride? For example, if you were usually 52/48, then that would be a pretty healthy swing.


Typically I'd be around ~51-52 / 48-49 L/R.
Last edited by: blayze: Oct 2, 18 7:06
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Re: Powertap P1 Question [JRC] [ In reply to ]
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blayze
Oct 2, 18 6:57
Post #6 of 9 (800 views)
JRC wrote:
I'm not that suprised,

I think in a lot of cases if one leg is down you will automatically scale power of both legs, as your body is used to outputing the same to both, it would probably take a fair amount of time ( weeks, months?) to reprogram yourself.

That's interesting... it does actually make sense when you articulate it that way... the 30% drop in power supports the scaling down theory.
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Re: Powertap P1 Question [blayze] [ In reply to ]
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blayze
Oct 2, 18 7:12
Post #7 of 9 (781 views)
Just spoke with the tech guys at PowerTap (Saris). They confirmed what you guys suggested:

1) Body scales down to remain reasonably balanced rather than significantly shifting power to the other leg in order to compensate
2) 52/48 healthy ----> 48/52 injured is actually a pretty significant swing

They said if the L/R balance wasn't working, then it would report flat 50/50 all the time and typically you'd see huge power spikes.

Thanks guys!
Last edited by: blayze: Oct 2, 18 7:13
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Re: Powertap P1 Question [blayze] [ In reply to ]
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exxxviii
Oct 2, 18 7:13
Post #8 of 9 (779 views)
blayze wrote:
Typically I'd be around ~51-52 / 48-49 L/R.
So, here is a quick by-the-numbers illustration. To help the illustration, I will base it on a 52/48 normal balance.

Say you were riding at 200W normally, that means that your left leg was driving 104W and your right leg 96W.
If you drop down 30% to 140W at your injured 48/52 balance, your left leg is driving 67W and your right leg is 73W

So, your left leg dropped its output 36% and your right leg dropped its output 24%.

But here is another pretty cool look. If your total power only dropped 10% to 180W, then your left leg would have dropped 17% to 86W. However, your right leg would almost have stayed even at a 2% drop to 94W.
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Re: Powertap P1 Question [exxxviii] [ In reply to ]
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blayze
Oct 2, 18 7:17
Post #9 of 9 (774 views)
exxxviii wrote:
blayze wrote:
Typically I'd be around ~51-52 / 48-49 L/R.

So, here is a quick by-the-numbers illustration. To help the illustration, I will base it on a 52/48 normal balance.

Say you were riding at 200W normally, that means that your left leg was driving 104W and your right leg 96W.
If you drop down 30% to 140W at your injured 48/52 balance, your left leg is driving 67W and your right leg is 73W

So, your left leg dropped its output 36% and your right leg dropped its output 24%.

But here is another pretty cool look. If your total power only dropped 10% to 180W, then your left leg would have dropped 17% to 86W. However, your right leg would almost have stayed even at a 2% drop to 94W.

You are a brilliant man! Thank you for breaking it down, your analysis helps me make sense of the data.
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