The Powercrank Thread

[coapman]

The use of extra muscles in cycling can increase pedal power but only when the correct combination of extra muscles is used. It is already obvious to you that attempting to use these extra PC muscles is causing a loss of power and this loss has to be occurring in the down stroke and while this loss of power will be reduced with further training, it will always exist as it does in circular pedalling. This means PC's cannot increase power output.

"An explanation of this loss of power in the downstroke due to the creating of an upstroke could be either (or both) of the following:

The first relates to pelvic stability. In my clinical experience of video assessment, the cyclists who use their hip flexors tend to hitch the pelvis up as they are trying to pull on the leg with the shortened hip flexor muscles at the top stroke. The result of this is that the stable pelvis base now moves and so the drive muscles are working from a moving base, and hence are Correct Bicycle Pedalling Techniqueworking at less than optimum.

The second relates to that difficult concept of neurophysiology. Basically, the motor cortex has a stored program for power delivery to the crank arm. Trying to overcome that program may result in a deadening of the most effective part of the pedal stroke.

Put simply, the brain cannot coordinate the up and downstroke as well as just the downstroke."

 

[JayKosta]

"
...
could be either (or both) of the following:
...
may result in a ..."

=============================================
Perhaps an interesting opinion from someone who might or might not know.

Worth hearing, but can its accuracy be trusted?
--- oops of course it can because of that "could be'!

Jay Kosta
Endwell NY USA

 

[coapman]

=============================================
Perhaps an interesting opinion from someone who might or might not know.

Worth hearing, but can its accuracy be trusted?
--- oops of course it can because of that "could be'!

Jay Kosta
Endwell NY USA

Well I do agree with his idea of the correct technique.
http://www.over40cyclist.com/correct-pedalling-technique-part-2/

 

[FrankDay]

"An explanation of this loss of power in the downstroke due to the creating of an upstroke could be either (or both) of the following:

The first relates to pelvic stability. In my clinical experience of video assessment, the cyclists who use their hip flexors tend to hitch the pelvis up as they are trying to pull on the leg with the shortened hip flexor muscles at the top stroke. The result of this is that the stable pelvis base now moves and so the drive muscles are working from a moving base, and hence are Correct Bicycle Pedalling Techniqueworking at less than optimum.

The second relates to that difficult concept of neurophysiology. Basically, the motor cortex has a stored program for power delivery to the crank arm. Trying to overcome that program may result in a deadening of the most effective part of the pedal stroke.

Put simply, the brain cannot coordinate the up and downstroke as well as just the downstroke."

This is simply silly.

If someone "hitches the pelvis" when trying to "pull up" they either have a weak core stability or are trying to pull up too hard. PowerCranks, at the most, make the typical rider only pull up about 10% more than they do now.

And, the neurophysiology question is an easy one. The basic pedaling coordination does not require any thinking (except, perhaps, when trying to learn the action when we are children). While some conscious control can sometimes be invoked most of this action takes place in the spinal cord/cerebellum and requires no conscious control. This system is perfectly capable of taking care of the push pull action of both legs at the same time because it is doing it now. PowerCranks only change the timing/muscle use a small amount from what is going on now. PowerCranks do not make cyclists pedal like Martians (unless Martians pedal more efficiently). Further, we all have a useful reflex here called the extension reflex. This reflex normally would come into play when one stepped on something sharp like a tack or something hot, like a fire. Withdrawing the foot from the object quickly reflexively results in the opposite leg pushing down hard to oppose this motion (it doesn't do much good to pull the leg down if you aren't also "jumping" away from the hazard). So, pulling up on the back stroke harder could actually enhance the pushing force. It is just that it can't come into play 5000 times an hour until the muscles are all trained up to the task.

 

[coapman]

So, pulling up on the back stroke harder could actually enhance the pushing force.

But you are conveniently forgetting the number 1 complaint of PC users, the pain in the saddle contact area of the body. This is caused by the increased pressure on the saddle where pulling up resistance has to be found and decreased pressure on the downward moving pedal resulting in a loss of down stroke crank torque.

 

[coapman]

Further, we all have a useful reflex here called the extension reflex. This reflex normally would come into play when one stepped on something sharp like a tack or something hot, like a fire. Withdrawing the foot from the object quickly reflexively results in the opposite leg pushing down hard to oppose this motion (it doesn't do much good to pull the leg down.

You are correct and this is the technique used by those who unweight the rising pedal between 6 - 8 o'c where rising leg weight has to be accelerated upwards. No training of the involved muscles is needed for this unweighting and the advantage can be seen in your speed increase from day one. But when you try to extend this reflexive effect by pulling or drawing the pedal up as PC's force you to do, the opposite effect takes place, resulting in a drop in power and speed.

 

[FrankDay]

A couple of weeks ago I was at an expo with the iCranks and got a fair number of reasonably experienced riders on the iCranks and was able to look at their technique and how changing them to PowerCranks immediately affected their technique. This is what I learned from the experience.

1. Very few people were awful on the upstroke. Most of the people who got on were very experienced riders. Almost everyone who got on the cranks had zero or minimal negatives being measured. There were a few who were really awful though. I did manage to remember to record one of them and I will post an example of his technique below.

2. Despite people showing no negatives when pedaling on regular cranks when we changed them to PC mode we saw increases in what they did on the backstroke and over the top. This is hard to explain as one wonders what the feedback is that causes them to change if there are no negatives on regular cranks. Feedback must be extremely subtle. Perhaps the iCranks are not sensitive enough to pick up very tiny or short duration negatives.

3. Almost everyone was weak across the top compared to the bottom of the stroke. Changing to PowerCranks mode demonstrably and immediately improved the amount of work done over the top by almost everyone. This is probably the area where most of the extra power improvements seen by training with PowerCranks is occurring.

4. One rider was especially difficult to explain. When he first got on on regular cranks he showed no negatives on either leg but his left leg was much stronger than his right, like 65/35. When we changed him to PowerCranks mode suddenly his right leg was now stronger than his left like 40/60.

5. It seemed to me that the real value of measuring technique (in most people) would not come from putting someone on a bike for 3 minutes at an expo when they are thinking about it but would come from looking at what they are doing after two hours when they are tired and not thinking about it.

Here is a screen shot of one of the more "awful" techniques seen. Note that he is doing 168 watts of forward power and 22 watts of negative power for a total of 146 watts to the chain, a 13% loss.

Here is what changing this person to PowerCranks mode did to him. Pay no attention to the power change. I am more interested in the technique change. The biggest change is in the last half of the upstroke and across the top. This is the area where most people saw change. Another difference is I don't think his pedaling is as "smooth" as on regular cranks. I attribute this to his having to think about what he was doing.

note, this is similar to a post on the pedaling technique thread but I post it again in the PowerCranks thread because of what is learned about PowerCranks from the experience.

 

[coapman]

note, this is similar to a post on the pedaling technique thread but I post it again in the PowerCranks thread because of what is learned about PowerCranks from the experience.

I already asked this question, is it possible to display this torque application in the more revealing sinusoidal graph format ?

 

[King Boonen]

...Pay no attention to the power change...

Err... What? No, I'm pretty sure you're going to have to explain that if you want this post to be taken at all seriously.

 

[FrankDay]

Err... What? No, I'm pretty sure you're going to have to explain that if you want this post to be taken at all seriously.

If I (or anyone) tried to imply that all it took to immediately see an increase in power from 146 to 415 watts is to put them on PowerCranks would you take that statement seriously? In order to help this rider pedal the PowerCranks I had to increase the resistance to slow the cadence which accounts for the power increase seen I am sure.

 

[FrankDay]

I already asked this question, is it possible to display this torque application in the more revealing sinusoidal graph format ?

Showing this data in cartesian coordinate graph format (sinusoidal to you) isn't more revealing as the data is exactly the same, it is just different. I, personally, find this format more intuitive regarding what is going on around the pedaling circle. Some day, when I have a lot of extra time, I will try to transpose this data into that format for you if you are unable to do it yourself.

 

[coapman]

Showing this data in cartesian coordinate graph format (sinusoidal to you) isn't more revealing as the data is exactly the same, it is just different. I, personally, find this format more intuitive regarding what is going on around the pedaling circle. Some day, when I have a lot of extra time, I will try to transpose this data into that format for you if you are unable to do it yourself.

Yes I am unable to do that, I hate computers. It is noticeable in that higher torque application, as I have always claimed, that the more torque you apply in your upstroke, the less torque will be applied in the down stroke of the other leg.

 

[coapman]

Yes I am unable to do that, I hate computers. It is noticeable in that higher torque application, as I have always claimed, that the more torque you apply in your upstroke, the less torque will be applied in the down stroke of the other leg.

" Powercranks. Greatest invention ever. For those who think you should pull up hard and train for it - these are for you. Do the least possible to get the pedal up and spend all your time mashing the cranks down in angry fashion using the glutes and hamstrings. It took these funky cranks for me to learn that - YMMV. I always mentally got the concept of 'get the pedal up and smash it down using the big muscles' but I could never get the physical aspect of it down until I got these. The first 3 months are infuriating, even for someone that thought they used to "pull up" well - the fact is you don't. Once I learned how to do it I could spend all the time thinking about pushing harder. Once I figured out the pushing harder part, my quads never died a million deaths like they used to. "

 

[Bio_McGeek]

When net power goes up, all the joint-action powers go up as well (see Elmer et al. MSSE 2011 Joint-Specific Power Production during Submaximal and Maximal Cycling). When knee flexion power increases sufficiently, power during the leg flexion phase exceeds the power required to lift the limb. This would result in positive net pedal power throughout the cycle. Which is what you found.
If you had done the same two powers with normal cranks you would probably get something very similar.

In order to help this rider pedal the PowerCranks I had to increase the resistance to slow the cadence which accounts for the power increase seen I am sure.

 

[FrankDay]

When net power goes up, all the joint-action powers go up as well (see Elmer et al. MSSE 2011 Joint-Specific Power Production during Submaximal and Maximal Cycling). When knee flexion power increases sufficiently, power during the leg flexion phase exceeds the power required to lift the limb. This would result in positive net pedal power throughout the cycle. Which is what you found.
If you had done the same two powers with normal cranks you would probably get something very similar.

While it is true that when we increase power we tend to do so in all the muscles we use I don't think that what we saw would occur if e just increased power on regular cranks because the increases were not equal around the circle. The change that I found that I thought significant was the fact that the power over the top increased more than the power across the bottom (which hardly changed at all in this example despite the large power change, especially on the right). We saw this difference regularly in those whose power didn't change and had little or no negatives on the upstroke on regular cranks. I used this example as an illustration because it showed how bad some really are but it also demonstrated the increase across the top relative to the bottom (plus, I had recorded it). As I have said many times, I believe the area where most people can improve their technique for the most power gain is across the top. Of course, increasing across the top is also facilitated by increasing the upstroke since the transitions are smooth.

 

[FrankDay]

When net power goes up, all the joint-action powers go up as well (see Elmer et al. MSSE 2011 Joint-Specific Power Production during Submaximal and Maximal Cycling). …
If you had done the same two powers with normal cranks you would probably get something very similar.

This from the abstract of Elmer et. al.

Relative knee extension power decreased (r(2) = 0.88, P = 0.01) and knee flexion power increased (r(2) = 0.98, P < 0.001) as P(net) increased.

This is the exact opposite of what my data shows. Knee extension is what causes power across the top. Going to PowerCranks showed a relative increase in the power across the top (knee extension) with the higher power (we also saw this even when power wasn't increased) Whereas Elmer found a relative decrease when on regular cranks. Therefore, I think the highlighted statement is demonstrably wrong.

 

[Bio_McGeek]

Elmer found a relative decrease when on regular cranks.

Relative, as in the relative contribution, went down slightly with increasing pedal powers. Absolute joint action powers went up with increased pedal power as you might recall from the figure in post 953.

http://forum.cyclingnews.com/showpost.php?p=1573203&postcount=953

 

[FrankDay]

Relative, as in the relative contribution, went down slightly with increasing pedal powers. Absolute joint action powers went up with increased pedal power as you might recall from the figure in post 953.

http://forum.cyclingnews.com/showpost.php?p=1573203&postcount=953

You are missing the whole point. In my example the power tripled while the "pushing" power (hip extensors) only doubled (approximately). This means that half of the power increase came from all of the other muscles increasing RELATIVELY MORE than the "pushers" to see that tripling of power whereas, Elmer's data says that people using regular cranks would have to push (hip extensors) more than triple harder to see the same increase because the relative contribution of the knee extensors went down. And, it was my observation that the area of the greatest improvement generally observed when a rider changed to PowerCranks was coming over the top, or the knee extensors.
Looking at Elmer's figure at how the knee is being used at TDC we can see that there is essentially no change in the work power there as power changed. (look at pedal power and knee power at TDC, 0º)

This is clearly not the case in my example. The only way the changes seen in my example could occur would be if the knee extenders initiated contraction much earlier and with more vigor than they do when riding regular cranks (where the crank comes over the top regardless of what those muscles do).

One can argue whether which pedaling pattern is more desirable or superior but it is hard to argue that the changes one sees increasing power is the same whether one increases power on regular cranks or does so by changing from regular cranks to PowerCranks (although you tried to). I look forward to hearing your argument that it would be detrimental for the rider to initiate contraction of the knee extenders 20-30º earlier in the pedal circle so power can be increased coming over the top relative to what is being done on the down stroke.

 

[FrankDay]

For Coapman and Bio McGeek and anyone else who doesn't understand

I transposed the polar graph to cartesian coordinates for the data previously posted (as best I could guessing at the actual values, your graph may vary slightly). I also adjusted the PC data to reduce it to show how the technique generally changed keeping the wattage at 146. Here you go

Edit: I noted something that may look "not right" to the discerning reader, that is that the power doesn't seem right on the graph. How could the power be 146 watts on the regular cranks and adjusted PC graph when the highest instantaneous power seen is barely above 146 watts (the total power is the average of all the instantaneous powers)? A similar issue exists for the PC graph. The reason is 146 watts was the power of both legs together and I am only graphing the left leg so the power is only 93 watts on regular cranks and 234 watts on PowerCranks. I have further modified the graph to show how the instantaneous power varies around this average power using the two techniques. Note that to maintain any given average power output the lower the instantaneous power gets below this average requires the instantaneous power to be that much higher somewhere else around the circle.

 

[coapman]

For Coapman and Bio McGeek and anyone else who doesn't understand

I transposed the polar graph to cartesian coordinates for the data previously posted (as best I could guessing at the actual values, your graph may vary slightly). I also adjusted the PC data to reduce it to show how the technique generally changed keeping the wattage at 146. Here you go

Edit: I noted something that may look "not right" to the discerning reader, that is that the power doesn't seem right on the graph. How could the power be 146 watts on the regular cranks and adjusted PC graph when the highest instantaneous power seen is barely above 146 watts (the total power is the average of all the instantaneous powers)? A similar issue exists for the PC graph. The reason is 146 watts was the power of both legs together and I am only graphing the left leg so the power is only 93 watts on regular cranks and 234 watts on PowerCranks. I have further modified the graph to show how the instantaneous power varies around this average power using the two techniques. Note that to maintain any given average power output the lower the instantaneous power gets below this average requires the instantaneous power to be that much higher somewhere else around the circle.

Powercranks are giving lower peak torque during down stroke, we already know that. The questions to be answered are, do Powercranks reduce a rider's peak torque during downstroke when he is at maximal power output and how does this maximal power value compare with the standard crank value. If you had got that rider to pedal at maximal power output on both standard and PC cranks while using the same gearing, we could have got that answer.

 

[FrankDay]

Powercranks are giving lower peak torque during down stroke, we already know that. The questions to be answered are, do Powercranks reduce a rider's peak torque during downstroke when he is at maximal power output and how does this maximal power value compare with the standard crank value. If you had got that rider to pedal at maximal power output on both standard and PC cranks while using the same gearing, we could have got that answer.

No we wouldn't have. We can't answer that question without training the person properly on PC's first. It is not possible to answer that question on the first ride.

From my perspective PowerCranks should not change the ability of the rider to use any of their muscles other than increase the ability slightly of what they do on the backstroke. What they do mostly is simply change the coordination of the muscles such that they are used at a more efficient time of the pedal circle (firing the quads earlier to improve what is done over the top, for instance).

 

[coapman]

No we wouldn't have. We can't answer that question without training the person properly on PC's first. It is not possible to answer that question on the first ride.

From my perspective PowerCranks should not change the ability of the rider to use any of their muscles other than increase the ability slightly of what they do on the backstroke. What they do mostly is simply change the coordination of the muscles such that they are used at a more efficient time of the pedal circle (firing the quads earlier to improve what is done over the top, for instance).

You should have enough experience on PC's and standard cranks to give it a try.

 

[FrankDay]

From Ken Lundgren of Elite Endurance Training Systems

“The following request to change your USA/Mountain category has been approved and processed by USA Cycling: Laura Slavin, Request to change category from Cat-1 to PRO -- APPROVED.”

Laura Slavin has had an incredible ascension. In May 2013, new to cycling she bought a flat-bar commuter, nearly didn’t get out of the lot, and now she is racing at the top level with a Pro USAC MTB license -- and the journey is JUST beginning.

In this picture she looks 12 to me but she is 31. Congratulations to her. Has anyone ever heard of anyone going from newbie to pro any faster?

 

[twothirds]

Possibly Linda Jackson.

 

[coapman]

The change that I found that I thought significant was the fact that the power over the top increased more than the power across the bottom (which hardly changed at all in this example despite the large power change, especially on the right). We saw this difference regularly in those whose power didn't change and had little or no negatives on the upstroke on regular cranks. I used this example as an illustration because it showed how bad some really are but it also demonstrated the increase across the top relative to the bottom (plus, I had recorded it).

This can be explained by the fact that unlike the top where an extra effort has to be made in getting the PC crank/pedal over TDC, the momentum of the downward leg is sufficient to take the same crank past BDC.