Can you explain why you think this is true?
Added: Like I will say that in 90% of scenarios, being clipped in has no impact on power output. But that is just because a person is either consciously or unconsciously not pulling up on the pedal enough to create force in that direction, NOT because there is some aspect of physics preventing it from happening.
" 11. Physics is a myth " ??
IF the spindle was only able to spin at one speed. Adding force is ADDITIVE, not subtractive. Plus who would be pulling up strong enough to yank the cleats out of their shoes would only be putting out ‘200 watts’ on the down stroke? Pulling up at 500 watts and only pushing down with 200 would likely throw people off their bikes. Granted the power isn’t the same, but it’s also not that lopsided (usually for more than a stroke or two)
Every time I’ve pulled up hard, I’ve been mashing hard too, and the net effect is climbing faster/wheel spinning occasionally. If it didn’t work, why does it work?
That’s true, but birds aren’t real!!
That seems true only if up and down strokes are in opposition (like in a tug-of-war). With cranks, your up and down are actually operating in the same direction, to rotate the chainring clockwise.
That said, I think the notion of pulling on the upstroke is of limited usefulness except in the grindiest bits of climbing. It’s blatantly obvious to anyone who’s gone up a grade they were over-geared for, or just stood up to power over a switchback, pulling up does work.
I tried Power Cranks many many years ago. Opened my eyes to the debate at hand here. I could barely ride 5 miles on flat roads yet my buddy who owned them got so adept riding them he could hang in criteriums with them.
Not sure what my point is other than your body is truly amazing how it can adapt and how much we take for granted the fact that the pushing down and weight of the leg pretty much drive the other leg up. Whether they increase your performance on the bike I do not know. I do know my hip adductors were on fire.
LoL, haven’t seen this thread for a while. Glad to see it hasn’t changed.
Isn’t the whole point of “increasing” the up stroke to reduce the amount of negative force applied to the cranks from the up leg. You can add force, but mostly you’re just lifting harder to take less away from the total system and begin your downstroke again sooner.
It’s 100% true that power added is power added. The fallacy is thinking that one is adding power by “pulling up” more than they were before.
You add power to the entire system, just as you said, by either increasing the gear ratio at a given rpm, or by increasing rpm. But the crank works as one unit, not two. The pedals are not independent of each other. A downward input on one end results in an upward reaction on the other end in a perfect 1:1 relationship. Put another way, with regards to your muscle effort, a “positive” effort in one portion of your stroke on one side results in a “negative” effort in the inverse portion of the stroke on the other side. Where people get it conflated is the overall power of the crank vs parts of the pedal stroke vs the physical perception of effort.
Yes, you can output 200 watts or 500 watts. Yes, your muscles can be engaged differently depending on inclination, total power, rpm, etc. The part that people get wrong is thinking they’re ADDING power simply by pulling on the upstroke. They might be doing other things, like resting their quads, but they’re not really adding power to the system in the way they think they are. They could only do that if the two pedal arms were independent of each other. You’re adding power to the crank as a whole by using a different gear or moving your legs faster, and that’s it. The rest is more or less irrelevant in terms of power output.
B I N G O !
Getting that rear foot “out of the way” is all you really want to do.
It’s a bit of a distinction without a difference though IMO.
It’s just a matter of scale. Pull up a little bit…you’re cancelling out a bit of dead leg weight. Pull up a lot in an all out sprint, you’re both cancelling out the weight of the leg plus adding addition power.
Either way…whatever effort you pull upwards with is transferred to power used to propel the bike forwards.
No, you add power by increasing your force on the pedals. That results in an increase of rpm assuming a constant gear.
I think that’s the part you have wrong, actually. A rider who’s putting 200W of power onto the downstroke can ADD power to the bottom/top/back of the rotation and thus increase the total power she’s applying to the pedals.
Your argument is that adding 50W to the upstroke automatically results in the downstroke being reduced to 150W to maintain the 200W prior power output, because power is constant at the same rpm if gearing is not changed. No… you can hold 200W on the downstroke and add 50W to the upstroke and you are now putting out 250W total force, which will result in increased rpm over time as your increased force accelerates the bike and rider.
RPM is tied to gearing and speed, not power. Changes in power lead to changes in rpm (assuming gearing held constant). And adding power with the “back” leg does NOT result in a “perfect 1:1” reduction of the power being applied to the downstroke.
I’m trying to look at this every possible way, and I just think you’re misunderstanding the basic physics of it.
I think it is helpful here to actually look at the basic physics tht produce thrust here.
Power = work/time
Work = force x displacement
If you increase the portion of the pedalstroke you are applying force, and the pedal is still moving, you are increasing displacement, thereby increasing work. If you are increasing work, and the time component (rpm) is not decreasing, you are increasing power.
Theres no way to rationalize that away.
Over-unders are really Under-overs.
This has been a fun discussion. I appreciate the replies. I don’t think I lack an understanding of the physics. I really want to respond! But I do think I’m running up against the upper limit of my ability to convey my thoughts clearly.
One thing I am 100% certain I’m right about: my opinion was definitely an unpopular one!
Y’all go out there and push down on the pedals or pull up on the pedals, or whatever — just pedal. One way or another that power’s coming out that crank!
What is a fender?
Mudguard for people in other parts of the world?
If it’s a Stratocaster, it’s a killer guitar!
EDIT: Although Telecasters are pretty killer too…
(My Cali Custom Strat is an awesome axe)
Mudguard, or a cunning way to create turbulence and slow some riders down? It’s directing the wind created by pulling up on the pedals down to the ground, so it’s obvious that if you can get it going hard enough, you could fly. HAH!!!
If you are adding power to a system that already has power applied to it, you are adding power. If that added power does subtract from the existing power, it’s not likely to be 100% of that existing power. Still, if it’s 50% of the existing power, it’s also adding power to supplant that because physics. I just know that during that crazy race I was stupid enough to do twice, I was able to scoot up the climbs faster than people who wallowed and ultimately had to huff it up on their feet. I have, on occasion, pulled up on the trainer (giving my poor butt a break) and it DOES add power to the crank, and I DO achieve the summit quicker. Being that it’s a trainer, is it possible that it is somehow incorrectly simulating the benefit, the ACTUAL increased power/torque across the crank spindle? I’d say unlikely, because that’s what the trainer ‘guts’ are supposed to do: Measure power…
IF there was an artificial limit on the power that could be transferred through the crank spindle, there WOULD be no gain in power because whatever governing mechanism would do its thing and limit the power delivered through that mechanism, but since there is effectively no limit (short of biomechanical and just human potential) and that the amount of power delivered at any moment is NOT static: ANY added power would be added to the output of the crank (possibly offsetting some of the normal power from the down stroke) with the result being more power, more torque, more speed, faster ascent. Is it the most efficient way to climb? Well, it stops the upstroke leg from being somewhat of a drag on the power of the downstroke leg. I mean, that alone would show that pulling up on the upstroke would introduce more power into the system, wouldn’t it?
But if you are pulling up in ERG mode, you should maybe think about dropping the demand, or just continue to rock your trainer because either way, you are riding it?
My muscles hurt after that race, muscles I had forgotten I had. Apparently someone should develop a weight trainer that allows people to lift their legs with weight resistance? Would standard squats accomplish that?
All you “pull-uppers” are just ~$200 away from having your best year ever. Power Cranks
You are going to crush all your personal bests after a year on these.
I guess you could say it depends whether the interval starts as an over or an under!