Poor man's Powercranks? (PPC)

Fday

when you expect me to answer questions about specifics of which I have no knowledge, what do you expect me to do, make up an answer?

Why don't you just tell everyone what is so impressive about the Coyle study and what it proves or doesn't prove about pedaling mechanics. You were the one who said you had no problems discussing issues like this. After all Dr. means teacher.

Fday

Clearly Mr. Stern was under the same misapprehension. (of course, you are not debating him). so, don't debate then, instruct us all. Afterall Dr. means teacher. Explain to me (and others) how Coyle calculated the statistical significance in his study that supposedly proves that "just pushing harder" is the best pedaling style. Oh, wait, he didn't bother to do that as I remember. Then compare that paper to the Luttrell study that does put forth their methods and calculates a statisical significance that would seemingly say something about pedaling dynamic and pedaling efficiency.

Let's have a rational discussion of the merits of these papers.

Frank

Fday

Of course the HF's can be just along for the ride. Don't need much of them to just pedal. But, why wouldn't you want the weight of the downward moving leg to be used to drive the bicycle forward instead of pushing the back leg up? That leg has all this potential energy at the top of the stroke, how can it be put to best use?

The question here is, does using the HF's (and hamstrings) more (or in a different way) result in better efficiency or more power, or both?

Fday

Might I remind you Dr. Coggan, this is what you replied earlier: "The difference being, of course, that I am perfectly happy to discuss the limitations of such studies based on what is known about them, as opposed to blowing off such criticism with comments such as "ask the authors"."

Apparently you are not willing to discuss the limitations of "such studies" with me but only will with those who hold you in awe. In medical school I was told Dr. means teacher but, if this keeps up, Webster may change it to Dr. means pompous you-know-what.

Try to get over making your point by calling people names. Let us discuss the merits of these studies. If my take on things has no merit I suspect those following this thread will be able to figure it out.

Frank

Fday

I am going to presume that Dr. Coggan really doesn't want to discuss the Coyle paper in question so I will make a few observations myself. From the Coyle paper itself (for those who are interested it can be downloaded here http://www.edb.utexas.edu/coyle/publications.php it is #40 on the list:

from page 9 to 11. "Group 1 had been performing endurance exercise training for 8.8 :t 0.9 yr, whereas group 2 had been
training for endurance for 5.0 :t 3.0 yr (P < 0.01; Table
1). . . . More importantly, the absolute V02 at LT (I.min-I)
was 9% higher in group 1 than in group 2 (3.99 :t 0.10
vs 3.67:t 0.17 (l.min-I; P= 0.11). " Burn more oxygen, put out more power. DUH!

From page 11. "One practical purpose of this study was to identify
some factors associated with time-trial cycling performance.
We observed that 40 km time-trial performance
was most closely related (r = -0.88; P < 0.01) to the
average absolute power output (i.e., watts) during the 1
h laboratory performance test (Fig. 2) and not power
relative to body weight." DUH!

from page 12. "Group 1was able to generate 11%more power during
the 1 h performance test than group 2 (P < 0.05; Table
4), and they maintained a 10% higher bicycling velocity
for 40 km (P < 0.05; Table 1)." It would appear that the elites were substantially more aerodynamic that the non-elites as a 11% increase in power should only result in an approximate 3.5% increase in speed if the aerodynamics were the same.

from page 13. "When the complex movement of cycling is considered
in its biomechanical entirety (kinematics, dynamics,
and muscular coordination), it is not surprising that a
measure of effectiveness based solely on the orientation
of the applied force fails to yield a meaningful measure
of the true "effectiveness" of the movement. It is clear
that any future research attempting to quantify effectiveness
must consider more than the orientation of the
applied pedal forces. This finding makes it unclear
whether feedback devices that allow a cyclist to improve
pedaling effectiveness (2,3,21) will lead to improved
performance." What could he possibly mean by "feedback devices that allow a cyclist to improve pedaling effectiveness"? Wonder if PowerCranks would fall into that category. Isn't that what Luttrell and Dixon tried to look at? Oh wait, according to some, this paper proves "just pushing harder is the key"! Forgot that. :-)

from page 13. "Differences between the power output and pedaling
cadence utilized in the present investigation and those
used in previous studies (10,11,16,18,19,21,27) made it
difficult to compare the present data with previous
biomechanical data. This is especially so since none of
the previous studies characterized competitive cyclists
under conditions similar to those of the 1 h performance
ride. A consistent conclusion of the previous studies
was that cyclists did not pull up on the pedal during
the upstroke. However, the present study found less
negative torque during the upstroke than the previous
studies." Tell me again that this paper proves that "just pushing harder is the key to success" and this paper proves such.

from page 13. "It is possible that the higher power production during
the downstroke displayed by group 1 compared with
group 2 resulted, to some extent, from a different
pattern of muscular utilization in the lower extremities
during each revolution. The results seen here could
indicate differences in the timing and activation patterns
of the lower extremity musculature and/or differences
in the intensity of the contractions of these same
leg muscles." Tell me again that this paper proves that "just pushing harder is the key to success" and this paper proves such.

from page 14. "In our previous study (8), the group of subjects who
reached LT at 66% VO2max(i.e., group L) appeared to
be different from the group of subjects who reached LT
at 82% of VO2max(i.e., group H) in factors other than
muscle mitochondrial activity. We speculated that these
"low LT cyclists" may not yet have developed proper
cycling technique, based upon the observation that their
blood lactate threshold was markedly lower when cycling
than when running uphill on a treadmill (8)." I thought technique didn't matter. Just push harder. But, what does Coyle know?

from page 14. "Additionally, we have
also observed a strong relationship between years of
endurance training and percent Type I muscle fibers (r
=0.75; P< 0.001). It appears that "elite-national class"
cyclists have the ability to generate higher "downstroke
power", possibly as a result of adaptations stimulated
by their greater number of years of endurance training." People who train more generate more power. DUH!

Next I found a discussion about this and some other papers here where both sides are presented.

http://www-gatago.com/rec/bicycles/tech/35184754.html

Here is an early comment:

"Because in the physics of pedaling the reduction of negative work _is_
positive work.

If the work of lifting the weight of one leg is 25 Joules, at 90rpm that's a
power rate of 37 Watts (for each leg). If each leg generates positive power
at a rate of 196 Watts, but the other leg is permitted to just ride up on
its pedal, then 37 Watts go into lifting the other leg, instead of
propelling the rider forward, so the power applied to speed is only 159
Watts per leg.

But if the racer uses each leg's own muscles to actively lift 90% of its
weight at 90rpm, then only 4 Watts is subtracted from the propulsive work,
and the power applied for forward speed is 192 Watts.

That's 20% more Watts. Positive power from lifting the weight of leg in the
upward phase. By real racers in an endurance performance."


Anyhow, let's see if we can stop the name calling and discuss the merits of these papers.

Piotr

This quote seems to address unweighing, not using flexors to propel the bike. It further ignores the simple logic that lifting the weight of the leg takes as much energy regardless whether it is done using its hip flexor or quads of the other leg or one's arm pulling a string. IOW, unweighing isn't free and I'm not sure where the "reduction of negative work" comes from. Spreading money over different accounts doesn't increase the amount of funds available.

Should a physicist invent a device that puts the leg back on top of a pedal stroke without any energy cost I'll be interested.

__________________
blog

Fday

Here is the problem with your analysis.

We have here a convergence of physics with biology. While from a physics point of view it should not make any difference if one just pushes harder or pulls some to increase the number of contractile elements involved in generating power, from a physiology point of view it does because we are limited in how much more we can push and pushing harder invokes more muscle fibres which, if they come from the same muscle means recruiting more of the less efficient fast twitch fibers, plus it means the same number of capillaries must feed these additional contractile elements, something else that cannot be expanded infinitely. Therefore, it is "easier" and more efficient to add these additional contractile elements, especially once one is close to the limit, using an entirely different muscle and blood supply, if one can train these muscles to do the work.

So, you are wrong, spreading money over several accounts, when it comes to biological systems, can mean there is more money to work with.

Frank

acoggan

First, I already replied to your questions about what I thought of Ed's study. Second, my point is that I am under no obligation to provide you with the most basic education that you so clearly need in order to understand such research. To give but a couple of examples of how poorly you understand the general topic at hand:

1) you once argued that VO2max was limited by CO2 transport (an even crazier hypothesis than some of the stuff Tim Noakes has put forth);

2) you've claimed that the energy required to passively turn the legs in a circle increases with the square of the cadence (a claim in violation of the 1st Law of Thermodynamics);

3) you don't understand enough about basic statistics to realize that you don't need a control group to show significance in a longitudinal design.

Given the above, is it any surprise that there is a limit to the extent to which I am willing to try to educate you?

acoggan

Actually, this is an important observation, since it clearly demonstrates that Group 2's tendency to better unweight the pedal on the upstroke did NOT result in increased efficiency.



Again, this is an observation worth noting, since you'd actually expect performance in a 40 km TT to be better correlated with power in W/kg than in W (since CdA correlates reasonably well with height - which correlates with mass - and with mass as well).



So?

(BTW, the 40 km performances in that study were obtained by self-report, and so should be taken with a grain of salt.)



As anyone who has ever read (or written) a scientific paper would realize, the feedback devices being referred to were those used/described in Ref. 2, 3, and 21.



No study ever proves anything. However, group 1 was more successful, and pushed harder on the pedals, so the statement you made is a reasonable interpretation of the results.



See above.



Read it again, Frank, and take special note of the use of the past tense: "We speculated that these
"low LT cyclists" may not yet have developed proper
cycling technique, based upon the observation that their
blood lactate threshold was markedly lower when cycling
than when running uphill on a treadmill (8)." IOW, while this hypothesis made sense to Ed (although not to me, since we also tested a subset of subjects w/o toe clips, and found that even w/o them the high LT subjects still had high LTs) after the completion of the study described in Ref. 8, it no longer made sense once he (Ed) went on to actually measure the pattern of force application during pedaling.



That's right: what separates elite from non-elite cyclists is not how they pedal, but how hard they pedal.

Next I found a discussion about this and some other papers here where both sides are presented.

http://www-gatago.com/rec/bicycles/tech/35184754.html

Here is an early comment:

"Because in the physics of pedaling the reduction of negative work _is_
positive work.

If the work of lifting the weight of one leg is 25 Joules, at 90rpm that's a
power rate of 37 Watts (for each leg). If each leg generates positive power
at a rate of 196 Watts, but the other leg is permitted to just ride up on
its pedal, then 37 Watts go into lifting the other leg, instead of
propelling the rider forward, so the power applied to speed is only 159
Watts per leg.

But if the racer uses each leg's own muscles to actively lift 90% of its
weight at 90rpm, then only 4 Watts is subtracted from the propulsive work,
and the power applied for forward speed is 192 Watts.

That's 20% more Watts. Positive power from lifting the weight of leg in the
upward phase. By real racers in an endurance performance."[/QUOTE]

So who is Ken Roberts, and what is his educational/scientific/research background that you would think he knows the first thing about what he is talking about?

acoggan

Yup - which is what makes Kautz's analysis of the cost of unloaded pedaling so important to understand.



That is your hypothesis. However, said hypothesis isn't consistent with the available data. For example, if what you claim were true, then the subjects in Coyle's group 2 (who unweighted more...some completely/all the time) would have been more efficient than the subjects in group 1. They were not, though, thus proving the saying:

"Ah, the great tragedy of science: the slaying of a beautiful hypothesis by one ugly fact."

acoggan

No, Ric wasn't - in fact, he previously tried to explain to you how it is possible to obtain statistical significance w/o a control group. What he was criticizing - rightfully so - was the experimental design.



Go read the paper: the statistical significance of differences between groups 1 and 2 were assessed using unpaired t-tests.



Earth-to-Frank: you can't get a scientific paper published w/o describing the statistical approach that was used.



You're confusing statistics and experimental design. The strength of the Luttrell study was that it was longitudinal in nature, not cross-sectional like Coyle's. However, the lack of an appropriate control group makes it difficult to ascertain the cause of the differences that were observed. IOW, the question isn't whether or not efficiency improved, it is why it improved.

acoggan

I would expect you to simply say "I don't know", rather than getting all huffy and defensive.



It's a valuable contribution to the literature because it demonstrates that differences in pedaling technique are not what differentiate elite from non-elite cyclists.

Fday

Well, I admit you did reply to the specific question as to whether this paper proves that just pushing harder is superior to pedaling in circles. Here is the exchange:

Frank: First, do you believe that study showed such (just pushing harder is superior)?

AC: No. However, it does provide evidence (of a cross-sectional nature) that there is no advantage to "pedaling in circles".

First, if you believe that this paper does not prove this hypothesis, why on earth do you sit silently when people repeatedly post on discussion groups that you participate in that it does? Beyond that, perhaps you would like to comment on a later paper of Coyle's #43 on the list, Kautz SA, Feltner ME, Coyle EF, Baylor AM: The pedaling technique of elite endurance cyclists: changes with increasing workload at constant cadence. International Journal of Sport Biomechanics 7:29-53, 1991 which shows that as the work load increases elite cyclists change their manner of pedaling to one that is more circular. What do you think this shows regarding pedaling style and how does it fit together with the earlier paper we have been discussing?

To answer your specific comments

It is like you to put words in my mouth. I don't think you have a clue what I really argued because it doesn't fit with your bias. Anyhow I never argues that CO2 transport is the limiter. In fact, CO2 transport is easy because CO2 is so water soluble compared to oxygen. What I argued was the limiter was getting rid of CO2 when the production goes up as muscles go anaerobic (when about 10 times more CO2 is produced for the equivalent energy produced aerobically). The failure to get rid of CO2 as fast as it is produced will eventually lead to a pH change incompatible with continued athletic performance.

Again, you misunderstand me, probably deliberately. I don't know if you have noticed, but the legs don't move in circles, only the feet do. The lower leg moves eccentrically and the upper, more masive, leg moves in a pumping motion. Calculate the energy requirement to move that leg in a pumping motion at different frequencies and tell me what you get.

Well, I thank you for that and the next time people criticize Dixon for not mentioning a control group I will be sure to let them know that you have stated unequivocably that under certain designs a control group is not necessary. Thanks. Enough with the name calling. Back to analyzing the papers.

Frank

acoggan

Because such statements aren't so far off-the-mark as to require a correction from me.



It shows what has long been known: the propensity to unweight the pedal depends in part on the power output.



Aside from the fact that it is the same subjects, I'm not sure what relevance it has to this discussion.



As it so happens, my "bias" is shared by 90%+ of exercise scientists...but anyway...



Guess I'll have to dig up your exact words, huh?



It doesn't matter: a body in motion stays in motion. IOW, while it takes more energy to accelerate one's legs up to a higher cadence, once at that higher cadence there is no physical reason (aside from friction) why it should take any energy at all to keep them turning at that cadence. You, OTOH, claim that your calculations show that the energy required to keep them turning increases with the square of the cadence...which says to me that you don't understand the 1st Law of Thermodynamics.



Indeed, in certain cases a control group isn't necessary (and for statistical purposes it is never necessary in an interventional study). Unfortunately, I don't think the Luttrell et al. study is one.