Page 2 - Huge difference in standing versus seated power

07-10.-2005, 02:18 AM

#16

lanierb

Registered User

Join Date: Aug 2004

Posts: 140

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by acoggan

The same as the SRM: power = torque x angular velocity. The only real difference is that with the PT the measurements are made at the hub, not at the crank, so that 1) the torque is reduced or increased, depending on the gear ratio and frictional losses in the chain, and 2) the angular velocity (of the hub) is increased or decreased, again depending on the gear ratio.

FWIW, I also generally produce significantly more power standing vs. seated, but only for ~1 min or less. I assume the difference is due to the contribution of my torso and arms to my anaerobic power output. Beyond that length of time, however, I'm better off seated, provided that I have low enough gears to keep my cadence above 65 rpm.

So here's a theory (but only a theory). From 20+ yrs of rock climbing, I have a very strong upper body relative to most cyclists (I can do one-arm pull-ups). I'm wondering if somehow when I stand I'm able to gain more efficiency using my upper body strength? If that's it I'm guessing there's not much I can do to bring my seated power up to the level of my standing power. 10% is huge though so it's a bit frustrating on the flats where standing doesn't help pace due to increased drag (of course on the hills I'm happy to just stand).

07-10.-2005, 02:46 AM

#17

RapDaddyo

Registered User

Join Date: May 2005

Location: Las Vegas, NV

Posts: 4,115

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by lanierb

I can see that, especially if your standing style is to actively use your torso and arms to leverage your body weight on the downstroke. When I'm off the saddle, I just use my torso and arms for balance and to position my frame so that my weight is centered over the BB on the downstroke. If I more actively used my upper body, I can imagine that I would generate more power than I do seated. But, I don't think I could sustain that pedaling style beyond ~1 min. I would reserve that for sprints.

07-10.-2005, 03:15 AM

#18

frenchyge

Registered User

Join Date: Apr 2005

Location: Kansas City, USA

Posts: 3,689

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by RapDaddyo

But, I don't think I could sustain that pedaling style beyond ~1 min. I would reserve that for sprints.

That's my thought. More power, yes. More 20-min power, no. Of course, if I were used to hanging from rock ledges for 20+ minutes at a time, then maybe things would be different.

07-10.-2005, 03:35 AM

#19

lanierb

Registered User

Join Date: Aug 2004

Posts: 140

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by frenchyge

That's my thought. More power, yes. More 20-min power, no. Of course, if I were used to hanging from rock ledges for 20+ minutes at a time, then maybe things would be different.

Yeah, most people stand for a bit to rest their seated pedalling muscles. I would characterize my hill climb style as sitting once in a while to rest my standing muscles. I can comfortably stand for 10 minutes at a time.

The thing is, even if that is the explanation it suggests to me that my cardiovascular system can easily handle 10% more power output than my legs can, and somehow I ought to be able to train my legs to take advantage of that.

07-10.-2005, 03:58 AM

#20

flapsupcleanup

Registered User

Join Date: Aug 2004

Posts: 113

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by frenchyge

The power calculation is done based on hub torque and hub rpm - not cadence. Body power is nearly equal to hub power, differing only by the small transmission losses in the drivetrain, which are ignored.

It's true that the hub/computer calculate a virtual cadence based on the torque pattern, but that's only for the rider's info - it's not used in the power calculation.

I'm not sure I agree with you on this one frenchy. If it calculates power based on hub rpm, then for a given power and speed your torque would have to remain constant regardless of the gear (cadence) you picked. But if you double your cadence, you halve the torque (at the pedals) to maintain the same power.

07-10.-2005, 04:04 AM

#21

flapsupcleanup

Registered User

Join Date: Aug 2004

Posts: 113

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by flapsupcleanup

Wait! I'll reply to my own post. Even though the pedal torque is cut in half above, because of picking a lower gear and therefore a larger moment arm at the rear cogs, the hub torque remains the same. And it works out. I stand corrected....by myself! I just love talking to me.

07-10.-2005, 04:12 AM

#22

frenchyge

Registered User

Join Date: Apr 2005

Location: Kansas City, USA

Posts: 3,689

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by flapsupcleanup

But if you double your cadence, you halve the torque (at the pedals) to maintain the same power.

That's true, but how'd you double your cadence and keep speed the same? By changing to a lower gear, of course, which changes the ratio of crank-arm torque that is transferred to the hub. Drive speed (rpm) from the pedals to the hub is multiplied by the transmission gear ratio, but torque is divided by the gear ratio, so that power remains constant regardless of gear selection.

In other words, changing gears may change pedal torque, but it doesn't change hub torque. Hub torque is a function of motion resistance only, whereas pedal torque varies with gear selection, too.

07-10.-2005, 04:13 AM

#23

frenchyge

Registered User

Join Date: Apr 2005

Location: Kansas City, USA

Posts: 3,689

Re: Huge difference in standing versus seated power

Quote:

Originally Posted by flapsupcleanup

Sorry, I was already typing a response.

Your correction stands correctly, however.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode