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Power Meters and Pedaling Effectiveness - Page 2

post #16 of 144
5/18/05 at 2:12pm
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Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by ric_stern/RST
to do a good test, you would need to randomise the order for all the trials, and repeat the test with each trial in a different order... obviously, this couldn't be done in a day so other variables would affect things...

HR isn't a predictor of fatigue and is only a predictor of how fast the heart is working. This is a 'proxy' for the effort that you're doing. The only thing that really matters is whether you can produce the desired power for the desired duration.

ric
Thanks, Ric. Actually, I did randomize the order of the tests, doing them in the order of 100-113-91. I didn't originally plan to do the 84, but threw it in at the end. I figured that if anything doing it at the end would bias the HR upwards. I do agree that I need to do the test again on a different day and in a different order. But, I am a bit surprised to learn that HR is not a predictor of fatigue if it is a proxy for effort and if greater effort leads to earlier fatigue. I understand what you are saying and accept it, but I just don't understand why.
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post #17 of 144
5/18/05 at 2:15pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
Thanks, Ric. Actually, I don't start off assuming that I need different crank lengths, or that I have an assymetric pedaling form, or that my pedaling stroke is inefficient. What I start off assuming is that I don't have any data except how I feel.
unlike sports such as golf, cycling is a gross motor control sport, where your legs/feet are constrained by the pedals, and there is little to alter (apart from e.g., comfort aspects and whether you may need e.g., "wedges" under your cleats).

Too many people place too much emphasis on e.g., 'correct pedalling', when even untrained sedentary people aren't that different in pedalling mechanics and efficiency compared to e.g., Pro cyclists. Mainly due to the way we are constrained when cycling. If you wanted to know how 'well' you pedalled then you would need to visit an (e.g.) exercise physiology or biomechanics lab that had force instrumented pedals (and not many places have such kit).

Quote:
By the way, I can't find an email address or web page for Kraig Willett. I think he is in the San Diego area. Do you know how to reach him?
Kraig and/or his brother (sorry can't recall) has/have posted here - but it was a long while ago. Try the biketech forum as Woofer suggests.

Ric
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post #18 of 144
5/18/05 at 2:23pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
But, I am a bit surprised to learn that HR is not a predictor of fatigue if it is a proxy for effort and if greater effort leads to earlier fatigue. I understand what you are saying and accept it, but I just don't understand why.
HR varies for many reasons, but tends to increase as you cycle at a higher power output, and decrease as you cycle at a lower power output. However, HR is only one aspect and it is cardiac output that is a better measure (CO being the product of stroke volume and heart rate).

HR will also vary due to other factors, as you have found out, by riding at a constant power and varying the cadence your HR will be different but performance isn't. Caffeine will raise HR, and temperature will decrease or raise it a given work rate at low and high temperatures respectively. Additionally, altitude, dehydration and anxiety can all cause it to fluctuate at a given power, as can fatigue, state of training, illness, and certain foods. Topographical conditions can also affect it.

I find that HR can vary dramatically under given workrates making it impossible to decipher what it may mean (other than the speed of your heart). What's important is whether you can generate the power that you need over the duration of the session irrespective of HR.

ric
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post #19 of 144
5/18/05 at 2:39pm
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Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by Woofer
Have you been fitted yet? That would be a good first step before changing anything else.
Yes, I was fitted in Philadelphia (Cycles BiKyle) before I moved to LV. I was fitted by Kyle personally. He seems to have good credentials, so I assume I have a properly fitted bike (Merlin Extralight). But, I haven't done any dynamic pedaling analysis on my bike.
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post #20 of 144
5/18/05 at 2:51pm
Thread Starter 

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by ric_stern/RST
HR varies for many reasons, but tends to increase as you cycle at a higher power output, and decrease as you cycle at a lower power output. However, HR is only one aspect and it is cardiac output that is a better measure (CO being the product of stroke volume and heart rate).

HR will also vary due to other factors, as you have found out, by riding at a constant power and varying the cadence your HR will be different but performance isn't. Caffeine will raise HR, and temperature will decrease or raise it a given work rate at low and high temperatures respectively. Additionally, altitude, dehydration and anxiety can all cause it to fluctuate at a given power, as can fatigue, state of training, illness, and certain foods. Topographical conditions can also affect it.

I find that HR can vary dramatically under given workrates making it impossible to decipher what it may mean (other than the speed of your heart). What's important is whether you can generate the power that you need over the duration of the session irrespective of HR.

ric
Thanks, Ric. I understand how and why HR will vary from day to day and based on temp, alt, caffeine, etc. But, I neutralized those variables by doing my cadence tests on the same day at the same altitude, temperature, and wind. My purpose was to explore the relationship between cadences at a given power level and effort, represented by HR as the best available proxy (I don't have a CO gauge on my bike at the moment -- know where I can get one?). So, I would naively assume that I would experience fatigue earliest at a cadence that produces the highest HR (113 in my test) and latest at a cadence that produces the lowest HR (84 in my test). Where am I going wrong?
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post #21 of 144
5/18/05 at 3:18pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
Thanks, Ric. I understand how and why HR will vary from day to day and based on temp, alt, caffeine, etc. But, I neutralized those variables by doing my cadence tests on the same day at the same altitude, temperature, and wind. My purpose was to explore the relationship between cadences at a given power level and effort, represented by HR as the best available proxy (I don't have a CO gauge on my bike at the moment -- know where I can get one?). So, I would naively assume that I would experience fatigue earliest at a cadence that produces the highest HR (113 in my test) and latest at a cadence that produces the lowest HR (84 in my test). Where am I going wrong?

I have to be brief as it's late here, but quickly... measuring cardiac output would be a highly invasive procedure...

to confuse matters, the most efficient cadence (i.e., the one that requires the least amount of energy and could be as low as ~ 60 revs/min depending on the actual power output) may not be the most optimal as your muscles maybe fatigued at a greater rate. The least efficient cadence may also not be the best, and the most *efficient* cadence will also increase (or decrease) at higher and lower power outputs.

In short, the most *optimal* cadence is the one that is most likely self-selected and is the one that allows you to produce the highest power over the duration concerned, under the conditions that you are riding.

In other words i wouldn't worry about either cadence or HR too much, just aim to generate the greatest sustainable power over the duration concerned

ric
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post #22 of 144
5/18/05 at 3:35pm
Thread Starter 

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by ric_stern/RST
I have to be brief as it's late here, but quickly... measuring cardiac output would be a highly invasive procedure...

to confuse matters, the most efficient cadence (i.e., the one that requires the least amount of energy and could be as low as ~ 60 revs/min depending on the actual power output) may not be the most optimal as your muscles maybe fatigued at a greater rate. The least efficient cadence may also not be the best, and the most *efficient* cadence will also increase (or decrease) at higher and lower power outputs.

In short, the most *optimal* cadence is the one that is most likely self-selected and is the one that allows you to produce the highest power over the duration concerned, under the conditions that you are riding.

In other words i wouldn't worry about either cadence or HR too much, just aim to generate the greatest sustainable power over the duration concerned

ric
Thanks, Ric. I was just kidding about the on-bike CO gauge. I started to put a 'just kidding' note after that comment, but I figured you would know that I wasn't being serious. Anyway, I gather that HR isn't a good predictor of fatigue. Maybe I'll have to do longer tests at a constant power and different cadences and see if there is a difference in when I 'blow up.'
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post #23 of 144
5/18/05 at 5:29pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
I designed a test that should have resulted in equal power. I have a nice long, relatively constant grade hill here. I did four 5-minute climbs (with 10 min. easy pedaling after each) in four consecutive gears, with cadences computed to maintain the same speed. The cadences were 113, 100, 91 and 84. My HRs were 150, 148, 145 and 143 respectively at the end of each 5 minute climb. Interestingly, the cadence that 'felt' the best was 91, even though I am most comfortable at about 100 on the flat. So, the feel and the HR were at odds with each other. Now, I would assume that HR is a predictor of fatigue and that I would have more endurance at the 84 cadence, even though I felt better at 91. Is HR a predictor of fatigue?
If it felt easier to pedal at 91 rpm instead of 84 rpm, you should pedal at 91 rpm - period. Your body has numerous sensors to determine just how stressful (actually, strainful) a particular activity or exercise might be, all of which are integrated to result in your perceived exertion. By contrast, HR is just one number, i.e., the rate at which your heart is beating - heck, it doesn't even tell you how much blood your heart is pumping!

(If I had a nickel for every misconception that has developed as a result of the widespread use of HR monitors, I'd be a rich man many times over.)
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post #24 of 144
5/18/05 at 6:14pm
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Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by acoggan
If it felt easier to pedal at 91 rpm instead of 84 rpm, you should pedal at 91 rpm - period. Your body has numerous sensors to determine just how stressful (actually, strainful) a particular activity or exercise might be, all of which are integrated to result in your perceived exertion. By contrast, HR is just one number, i.e., the rate at which your heart is beating - heck, it doesn't even tell you how much blood your heart is pumping!

(If I had a nickel for every misconception that has developed as a result of the widespread use of HR monitors, I'd be a rich man many times over.)
Thanks. Actually, my test results were kind of interesting, not so much that my HR was lower with lower cadence at a constant speed (and power), but that I was so uncomfortable at 113. Now, I go 113 on the flat all the time with no problem (even though I am a little more comfortable at about 100). But, with the added stress of climbing, I just couldn't believe how hard it was to push the cadence up to 113 and keep it there. I just kept looking at my countdown timer thinking, "God, isn't this over yet?" Likewise, I was kind of surprised that I wasn't more comfortable at the 84 vs. the 91 cadence. I kept looking at my HR monitors (one on the bike and one on my wrist), not believing that my HR was a couple of beats lower than at 91, yet I felt less comfortable. Interesting.
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post #25 of 144
5/19/05 at 1:58pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
Anyway, I gather that HR isn't a good predictor of fatigue....
Without going into a serious exercise physiology discussion, perhaps it would be helpful to think of things in this way: a lot of research has gone into discerning the cause(s) of fatigue (which is the inability to maintain a power output specific to the circumstances of just what is being tested - eg: 4.5W/kg to fatigue) during endurance performance; although no one variable can be singled out as "the cause", there are many to consider....one that most people are familiar with is muscle glycogen availability; so, given that fatigue is a multi-factoral phenomena, no one variable that you monitor will give you the whole story (and as mentioned, heart rate is not even one of those variables anyway). This is one reason why training with power is so advantageous...you are measuring performance directly, not indirectly via a physiologic response (which is always confounded by other physiologic responses). End result...preempt as many causes of fatigue as you can, then "i wouldn't worry about either cadence or HR too much, just aim to generate the greatest sustainable power over the duration concerned".
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post #26 of 144
5/19/05 at 2:32pm
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Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by Smartt/RST
Without going into a serious exercise physiology discussion, perhaps it would be helpful to think of things in this way: a lot of research has gone into discerning the cause(s) of fatigue (which is the inability to maintain a power output specific to the circumstances of just what is being tested - eg: 4.5W/kg to fatigue) during endurance performance; although no one variable can be singled out as "the cause", there are many to consider....one that most people are familiar with is muscle glycogen availability; so, given that fatigue is a multi-factoral phenomena, no one variable that you monitor will give you the whole story (and as mentioned, heart rate is not even one of those variables anyway). This is one reason why training with power is so advantageous...you are measuring performance directly, not indirectly via a physiologic response (which is always confounded by other physiologic responses). End result...preempt as many causes of fatigue as you can, then "i wouldn't worry about either cadence or HR too much, just aim to generate the greatest sustainable power over the duration concerned".
I accept everything you say. But, from a practical standpoint, I find it hard to believe that I can generate the greatest sustainable power over the duration concerned at a cadence of, say 100 on the flat and 90 climbing one day and the next day it is 110 and 80 respectively. Yes, I can see that HR may be all over the place, but I can't get my mind around the notion that my optimal cadence is going to be all over the place from day to day. I have limited things I can monitor and manage on the bike and cadence at a certain power output is a big one. Do I have to start every ride thinking, "Gee, I wonder what my optimal cadences are today?" I've picked gears to get me to a target cadence given the situation since the first day I rode. That'll be a hard habit to break.
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post #27 of 144
5/19/05 at 2:44pm
Thread Starter 

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by acoggan
If it felt easier to pedal at 91 rpm instead of 84 rpm, you should pedal at 91 rpm - period. Your body has numerous sensors to determine just how stressful (actually, strainful) a particular activity or exercise might be, all of which are integrated to result in your perceived exertion. By contrast, HR is just one number, i.e., the rate at which your heart is beating - heck, it doesn't even tell you how much blood your heart is pumping!

(If I had a nickel for every misconception that has developed as a result of the widespread use of HR monitors, I'd be a rich man many times over.)
Dear Mr. Coggan, thanks again for your input. I wanted to send you an email on a non-cycling exercise physiology question, but can't do that from this site. Could you please send me an email and let me know how I can contact you?
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post #28 of 144
5/19/05 at 2:45pm

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by RapDaddyo
I accept everything you say. But, from a practical standpoint, I find it hard to believe that I can generate the greatest sustainable power over the duration concerned at a cadence of, say 100 on the flat and 90 climbing one day and the next day it is 110 and 80 respectively. Yes, I can see that HR may be all over the place, but I can't get my mind around the notion that my optimal cadence is going to be all over the place from day to day. I have limited things I can monitor and manage on the bike and cadence at a certain power output is a big one. Do I have to start every ride thinking, "Gee, I wonder what my optimal cadences are today?" I've picked gears to get me to a target cadence given the situation since the first day I rode. That'll be a hard habit to break.
If it helps, the research fully supports your issue of performing better at one cadence one day and another the next. That's not to say that one is cadence better then the other, quite the opposite. Efficiency and performance are typically only effected by very large changes in cadence: eg when comparing 60rpm to 100rpm or more. So, I would suggest that if you saw any noticeable differences in performance, it was because of other factors rather than cadence.
And just to muddy the waters some more, "optimal cadence" (depending on how you want to define that) can chance within a single ride as muscle fibers fatigue.
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post #29 of 144
5/19/05 at 2:48pm

Re: Power Meters and Pedaling Effectiveness

In other words, all you really need to do is aim to generate the most power over the duration concerned, and don't worry about your HR or cadence.

ric
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post #30 of 144
5/19/05 at 2:50pm
Thread Starter 

Re: Power Meters and Pedaling Effectiveness

Quote:
Originally Posted by Smartt/RST
If it helps, the research fully supports your issue of performing better at one cadence one day and another the next. That's not to say that one is cadence better then the other, quite the opposite. Efficiency and performance are typically only effected by very large changes in cadence: eg when comparing 60rpm to 100rpm or more. So, I would suggest that if you saw any noticeable differences in performance, it was because of other factors rather than cadence.
And just to muddy the waters some more, "optimal cadence" (depending on how you want to define that) can chance within a single ride as muscle fibers fatigue.
Well, that settles it then. Cycling is too complicated! I'll have to take up swimming.
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