L/R pedal powermeter data and bike fit
Road cyclist here. Just got dual sided power meters (pedals) and I have learned a LOT about how I pedal (...er, or at least I have a lot of data on how I pedal :lol:)
One of the many things that I have noticed is that I can alter my "Peak Power Phase" (which is defined by Garmin as the number of degrees through which each leg delivers 50% of it's total power) simply by moving the saddle up/down 1mm or 2mm (!) For example if I move my saddle DOWN 2mm from my normal position,my PP arc goes from 70 degrees to 77 degrees which seems like a significant change (my full power arc is ~225 degrees). So assuming my total power output has not dropped (which I haven't tested yet), it seems like lengthening the PP arc could reflect a smoother delivery of power (ie, so maybe my normal saddle height was a little too high). So (even if my interpretation of this is incorrect) it sure seems like such power phase data could be used to help dial in position for optimal performance (at least for a given discipline). However, I can find very little information on this topic but am sure it must exist. Does anyone know of any good resources on this (or have any info they could share)? |
Originally Posted by ExMachina
(Post 21287199)
So assuming my total power output has not dropped (which I haven't tested yet), ...
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My guess is that a shorter arc will tire one's legs more quickly at the same power. There might be a simple test: in erg mode, set the power on your trainer to say 110% FTP, then change the length of your peak force arc. See what happens and report.
I realize that this test is more rigorous than one would encounter on a climb, still I think the principle is the same. I know when I want to do long (for me) VO2max intervals, I get noticeably less fatigued if I engage my hams, glutes, and calves to increase the length of my power arcs. |
Originally Posted by asgelle
(Post 21287325)
If your power doesn't change, what difference does how you apply the force make?
In terms of the pedal stroke, superficially: Power=(Force*Distance)/Time So decrease the pedal stroke's distance (its arc length) and the rider must increase the force to keep the power the same. So there's likely an optimum arc length where fatigue is minimized |
Originally Posted by ExMachina
(Post 21287453)
So there's likely an optimum arc length where fatigue is minimized
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Fatigue is more than just putting less power out, you still feel fatigue when you get off the bike.
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I can do a lot of hard riding, especially climbing, or very long rides. I will feel fatigued and experience a power loss. However, I also can do some decent climbs and short rides of 25 miles for instance and at no time feel fatigued. But when I go to push the pace as fast as I can for several miles or on longer climbs even though I definitely do not feel fatigued or weaker but in reality, I still am actually experiencing fatigues as indicated by reduced power and slower speeds at the same subjectively perceived output.
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Originally Posted by Seattle Forrest
(Post 21287797)
Fatigue is more than just putting less power out, you still feel fatigue when you get off the bike.
Just as with efficiency, people redefine it to mean whatever they want it to mean with the result no one knows what the other is talking about and we get into endless arguments because of the confusion. |
Originally Posted by asgelle
(Post 21287457)
Since fatigue is the inability to maintain the desired power, by definition, changing fatigue means changing power. You can't have it both ways, if different pedal strokes don't change power, fatigue must be the same; if fatigue is different, you can't be seeing the same power.
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Originally Posted by ExMachina
(Post 21288080)
I disagree. Fatigue is a function of time also. For example I know I fatigue much faster (at the same power output) if I try to keep my cadence artificially high. So there are most definitely better/worse ways to deliver energy to the bike.
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Somebody here gets it.
Until you get grossly out of fit range for a riding position (hoods, drops, time trial, bar tops), you won't see an appreciable difference in performance. Next, good luck taking the "pedal in circles" bull **** or some other super thought aware pedaling into some hard intervals. You get efficient riding hard by riding hard, often. Your body is forced to figure out how to adapt to the stress. Could be a touch of cadence, could be a touch of pedaling style, etc.... Also, this awareness isn't available "in a race" or when paying attention to your wheel in a paceline. So, if you're not a pro or someone riding a LOT..........you won't reinforce the habit through some kind of situational awareness just during an easy enough workout that you can bother to watch such things. You can spot the 'onset' of fatigue after the fact with watching your cadence go from a robot metronome like 100rpm on the do to a little sawtooth pattern later in the interval as you approach fatigue. If I were you, instead of too much worry about that.......I'd set the seat up with basic normal fit rules and use those pedals to do some structured training. Again, you get efficient riding at 105% by riding at 105%. Not by riding at 50% and staring at a pedal efficiency metric. |
Originally Posted by asgelle
(Post 21288088)
I don't see what you're disagreeing with.I never said different pedaling styles don't result in different times to fatigue, only that as long as power remains the same, fatigue is also equal.
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Since this thread seems to have gone off the rails almost immediately, I'd like to restate my original question:
Are there any resources that anyone knows of (websites, book, scientific paper) that discuss how a power meter can be used to optimize position on the bike? If not that's cool. |
I have the Garmin Vector 2 L/R. Via the Garmin 820, I can generate all kinds of graphs. I have not found any use for them yet, supporting material or a coach that is interested in the data.
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Originally Posted by ExMachina
(Post 21289555)
Since this thread seems to have gone off the rails almost immediately, I'd like to restate my original question:
Are there any resources that anyone knows of (websites, book, scientific paper) that discuss how a power meter can be used to optimize position on the bike? If not that's cool. I was doing intervals again on my resistance rollers this evening and testing power arcs while suffering along. So, I'd be holding power, legs getting tired, and then without looking at my device, I'd activate my glutes and start raising my toes at ~11 o'clock. I'd look down and my power had gone up 8 watts. Then I'd maintain that motion and reduce cadence a hair, dropping my power down to where I had been trying to keep it. My legs definitely felt less stress. It took concentration to maintain that arc, but that should go away with practice. I definitely have a saddle height sweet spot where I develop more power, mostly from pushing forward/pulling back with a particular knee bend in each spot. The below is is a useful video to watch for pedaling action and saddle height. Though their position seems different, they're just rotated forward on the bike. Their actual position w/r to the BB isn't different. If you imagine the riders rotated back so their torsos are in the road position, you'll see what I mean. We can see their muscles fire as they go through the pedal stroke. If you watch that famous video of Pantani vs. Lance on Ventoux, you can see similar pedaling. |
Originally Posted by Hermes
(Post 21290091)
I have the Garmin Vector 2 L/R. Via the Garmin 820, I can generate all kinds of graphs. I have not found any use for them yet, supporting material or a coach that is interested in the data.
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Seems to me muscle memory is what drives power arc, smoothness and torque effectiveness. I'm sure bike fit can hurt your numbers, but drills that create a full smooth power delivery like single pedal and high cadence are the way to really drive improvement.
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Originally Posted by Carbonfiberboy
(Post 21290112)
Their actual position w/r to the BB isn't different. If you imagine the riders rotated back so their torsos are in the road position
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Originally Posted by jadocs
(Post 21306050)
Not sure what you mean, you don't believe they are more forward over the BB and that the only difference is they are rotated at the hip more?
I meant that they are rotated around the BB. Of course their position w/r to the horizontal is very different from the road position. Even with their saddles as far forward as the rules allow, they're up there on the nose. But their bodies w/r to their various parts, not w/r to the horizontal are approximately in the road position. And therefore their pedaling action and muscle usage is not very different from a rider in the usual road position w/r to the horizontal - with a big caveat: Notice that their upper bodies are absolutely stationary. These women are powerful swimmers with well-developed upper bodies, yet there is no visible upper body muscle flexure going on. They pedal with their legs. Among road cyclists, one sees some riders who bob a lot, using their more upright position to push on their legs with their body weight, Newton's 3rd law in action. This is all very interesting to me. |
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