Pedalling technique
Comments
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My limited left-right data (downstream of BB - Computrainer FWIW, which I wouldn't place a lot of bets on) suggested I was around 46-49% on the left side during aerobic power riding (greater imbalance at lower powers), with a trans-tibial amputation / prosthetic cycling leg.
I've no idea about my sprint power balance, but it would be far greater imbalance. Note that my sustainable aerobic power pre and post amputation was the same, but my peak sprint power declined by ~ 250W.
I can't readily ride Wattbikes because my prosthetic leg is very sensitive to Q-factor (a small change creates big problems). Well I suppose I could ride one, but I'd have to make adjustments to my leg to be able to, and I try avoid making such adjustments like the plague as when the adjustment is out, I end up putting holes through the skin in my leg. I had to normalise my bikes to use same cranks to avoid this issue.0 -
Q factor is a Red Herring. Getting too used to a certain position be it Q factor or saddle height or anything similar is a fault. A true master can use any sword, bow, gun, or cycle. One should be able to ride any machine effectively even if the Q factor is a few inches wider than usual.
If you are unable to ride a machine because the Q factor is not to your liking, that is a fault with you and your coach not the machine.
Obviously, Alex, I'm referring to people without prosthetic limbs.0 -
I wouldn't be so sure about that.Max Bridges wrote:Q factor is a Red Herring.
http://www.ncbi.nlm.nih.gov/pubmed/22612455
A 5W improvement in submaximal power output is nothing to sneeze at, from something as simple as narrowing the Q-factor.0 -
Alex_Simmons/RST wrote:
I wouldn't be so sure about that.Max Bridges wrote:Q factor is a Red Herring.
http://www.ncbi.nlm.nih.gov/pubmed/22612455
A 5W improvement in submaximal power output is nothing to sneeze at, from something as simple as narrowing the Q-factor.
Questions.
1 what is Q factor on a normal road bike?
2 did the 24 cyclists know Q factor was being tested?
3 did those that conducted the tests know Q factor was being tested?
4 did the cyclists or those conducting the tests know which Q factor was expected to be most efficient?
5 was the order of the tests randomised?
6 an improvement of 1.5% to 2% or 4 to 5 watts is insignificant compared to 3% normal variability in human performance, so is the improvement statistically significant?
7 how accurate was the power meter?0 -
Alex_Simmons/RST wrote:
I think you need to be careful when considering such data, as it is not showing you independent force data from each leg, rather it is showing you the combined force data from both legs.Max Bridges wrote:The scan shown by the Wattbike shows very different patterns for each leg. My left more powerful leg displays a massive half peanut but my right leg more a nice efficient circle. I assume my left more powerful leg generates more power by pushing harder on the down stroke?
IOW the peanut shape you describe is showing you the combined forces from both legs for one half of the pedal stroke (i.e. when one or the other crank is forward of the BB). It is not showing the forces isolated to each leg for a full pedal stroke.
Wattbike measures forces downstream of the bottom bracket, and hence cannot make such a distinction of independent leg/crank forces.
Which is why, when you examine pedal forces independent with pedal or crank based gauges, you will often see a different pattern than when you consider the split in the manner that a Wattbike does.
You sell SRM Power Meters and Quarq Power Meters, I assume you don't sell Wattbikes? Your comments are hardly those of an independent expert.0 -
Is this Trev again..?0
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Stalin wrote:Alex_Simmons/RST wrote:
I wouldn't be so sure about that.Max Bridges wrote:Q factor is a Red Herring.
http://www.ncbi.nlm.nih.gov/pubmed/22612455
A 5W improvement in submaximal power output is nothing to sneeze at, from something as simple as narrowing the Q-factor.
Questions.
1 what is Q factor on a normal road bike?
2 did the 24 cyclists know Q factor was being tested?
3 did those that conducted the tests know Q factor was being tested?
4 did the cyclists or those conducting the tests know which Q factor was expected to be most efficient?
5 was the order of the tests randomised?
6 an improvement of 1.5% to 2% or 4 to 5 watts is insignificant compared to 3% normal variability in human performance, so is the improvement statistically significant?
7 how accurate was the power meter?
Well if you can't be bothered to access the full item to answers these yourself, if you are lucky perhaps Dr Xav might come along and answer them.0 -
Stalin wrote:You sell SRM Power Meters and Quarq Power Meters, I assume you don't sell Wattbikes? Your comments are hardly those of an independent expert.
Whether or not I sell power meters or tiddlywinks doesn't change the facts about what Wattbikes and power meters actually measure. The load unit on a Wattbike is downstream of the bottom bracket and hence left and right power is a measure of power from both legs when either the left or right crank is forward of the bottom bracket.
That's the same for a Quarq, and Power2Max, and Computrainer or any power measurement unit where the forces are measured downstream of the BB (i.e the spider, the chain, cogs, rear hub, wheel or tyre).
But hey, you don't need to believe me, you could just read the Wattbike website that explains where they measure the forces:
http://wattbike.com/au/wattbike/accurac ... alibrationWattbike Website wrote:It measures absolute mechanical power in Watts with the amount of power produced measured from the sum of all the forces applied to the chain through the cranks. The forces are measured by one load cell and sequencing of the applied force is calculated according to crank position (determined by the location of two magnetic sensors on the crank).
Measurement of each leg independently requires force measurement be done upstream of the bottom bracket, e.g. force sensors would be required in each crank arm (or pedal).0 -
Alex_Simmons/RST wrote:Stalin wrote:Alex_Simmons/RST wrote:
I wouldn't be so sure about that.Max Bridges wrote:Q factor is a Red Herring.
http://www.ncbi.nlm.nih.gov/pubmed/22612455
A 5W improvement in submaximal power output is nothing to sneeze at, from something as simple as narrowing the Q-factor.
Questions.
1 what is Q factor on a normal road bike?
2 did the 24 cyclists know Q factor was being tested?
3 did those that conducted the tests know Q factor was being tested?
4 did the cyclists or those conducting the tests know which Q factor was expected to be most efficient?
5 was the order of the tests randomised?
6 an improvement of 1.5% to 2% or 4 to 5 watts is insignificant compared to 3% normal variability in human performance, so is the improvement statistically significant?
7 how accurate was the power meter?
Well if you can't be bothered to access the full item to answers these yourself, if you are lucky perhaps Dr Xav might come along and answer them.
I managed to access the PDF.
It seems the order of the 5 minute tests was randomised. Research such as this should in my opinion be encouraged, however I also believe studies should be rigorously criticised.
I note a Powertap was used to measure power, accuracy and repeatability is claimed by the manufacturers to be + / - 2% and measuring gas bags etc is known to be problematical.
More studies are needed and I would like to see more accurate power measurement than a Powertap. Perhaps setting up more than 1 power meter, ie, SRM at the cranks, and a Powertap on some sort of rig which enables mechanical checking of the power meter / or power meters?
If you are trying to prove advantages of 1.5% to 2% you need to measure power significantly more accurately than in this study.
http://onlinelibrary.wiley.com/store/10 ... 1c1333a4a8
I only scanned it quickly, did I miss anything about how often accuracy of the Power meter used was checked? Was it before each cyclist or before each Q factor test or just before all the tests? Was temperature controlled? There is mention of heart rate being recorded but no mention of what it was used for.
Anyway, hopefully more studies can be done. I have done 20 min tests myself on Q factor. I found no measurable difference in sustainable power output with different Q factors, but I did manage to average more power when I alternated foot position on the flat pedals moving feet from as close to the cranks as possible and as far away as possible. These tests are however rather limited as I only had power, heart rate and feel. Also I'm my only subject and it is entirely possible I detected something I wanted to detect and influenced the results.0 -
If you accessed the .pdf you obviously didn't read it. Why you need to change your username all the time is beyond me, you keep getting banned on the TT forum but not on here.
Read the paper referenced in the study about the accuracy of Douglas bags. Also note the part about the calibration check of the Powertap. I suggest you brush up on your stats and understand what statistical significance means before pretending to dismiss studies without actually reading them ...
Xav0 -
xavierdisley wrote:If you accessed the .pdf you obviously didn't read it. Why you need to change your username all the time is beyond me, you keep getting banned on the TT forum but not on here.
Read the paper referenced in the study about the accuracy of Douglas bags. Also note the part about the calibration check of the Powertap. I suggest you brush up on your stats and understand what statistical significance means before pretending to dismiss studies without actually reading them ...
Xav
To quote the paper,
"The Powertap was statically calibrated with weights of known mass to ensure its accuracy, and is comparable with the Schoberer Rad Messtechnik system in its accuracy (Gardner et al., 2004)."
How often did you check the accuracy of the Powertap? Did you control temperature and core temperature of subjects?
Powertaps are not very accurate.
http://www.ncbi.nlm.nih.gov/pubmed/15235334
I have asked reasonable questions about your study, you should answer them rather than make pathetic personal attacks.0 -
You should have read the paper first.Stalin wrote:Did you control temperature and core temperature of subjects?
Climate was controlled to w/in 1 deg Celsius, and core temperature has nothing to do with the calibration of a Powertap :?
Xav0 -
xavierdisley wrote:You should have read the paper first.Stalin wrote:Did you control temperature and core temperature of subjects?
Climate was controlled to w/in 1 deg Celsius, and core temperature has nothing to do with the calibration of a Powertap :?
Xav
I said core temperature of the subjects not the Powertap. If your subjects were getting hotter as the tests went on it would affect their power output, or their ability to put out the same power.
How often did you test the accuracy of the Powertap? Why use a Powertap? Hardly the best way to measure power, particularly when you are looking at differences of 1- 2 %.0 -
Stalin wrote:I said core temperature of the subjects not the Powertap. If your subjects were getting hotter as the tests went on it would affect their power output, or their ability to put out the same power.
That is a non starter when you understand that we were measuring gross mechanical efficiency. There was no time effect.How often did you test the accuracy of the Powertap? Why use a Powertap? Hardly the best way to measure power, particularly when you are looking at differences of 1- 2 %.
We did multiple calibrations of all the equipment, the Powertap was IIRC 3 times over the course of a few months and it was extremely stable and didn't change. If it had we would have sent it back. There was nothing wrong with using a Powertap for this experiment, especially when you consider that cadence and gear were fixed and think about how a Powertap calculates power. The gas analysis machines were recalibrated and checked multiple times even within/ sessions as you have to be very exact if you want the level of accuracy that we were able to achieve.
Xav0 -
xavierdisley wrote:Stalin wrote:I said core temperature of the subjects not the Powertap. If your subjects were getting hotter as the tests went on it would affect their power output, or their ability to put out the same power.
That is a non starter when you understand that we were measuring gross mechanical efficiency. There was no time effect.How often did you test the accuracy of the Powertap? Why use a Powertap? Hardly the best way to measure power, particularly when you are looking at differences of 1- 2 %.
We did multiple calibrations of all the equipment, the Powertap was IIRC 3 times over the course of a few months and it was extremely stable and didn't change. If it had we would have sent it back. There was nothing wrong with using a Powertap for this experiment, especially when you consider that cadence and gear were fixed and think about how a Powertap calculates power. The gas analysis machines were recalibrated and checked multiple times even within/ sessions as you have to be very exact if you want the level of accuracy that we were able to achieve.
Xav
Gross mechanical efficiency is affected by temperature.
You only checked calibration of the Powertap 3 times. The fact it gave the same readings when you checked it with weights does not mean it was giving accurate readings when actually in use. It could have been drifting all over the place. Frankly it should have been tested before every session. PowerTaps are known to drift.0 -
Gross mechanical efficiency is affected by temperature.
I think you need to brush up on your physiology.
You do realise the difference between checking a static calibration and setting the zero offset (done within sessions)? I think you're just being argumentative for the sake of it
Xav0 -
Stalin wrote:You only checked calibration of the Powertap 3 times. The fact it gave the same readings when you checked it with weights does not mean it was giving accurate readings when actually in use. It could have been drifting all over the place. Frankly it should have been tested before every session. PowerTaps are known to drift.
Whether or not your ignorance is deliberate or feigned, this shows a sizeable lack of understanding between validating the slope calibration of a power meter is stable over time, and checking for changes in torque zero before/during/after an exercise bout.
These are totally different things.0 -
Time-trial performance deteriorates in the heat. This might potentially be the result of a temperature-induced decrease in gross-efficiency (GE). The effect of high ambient temperature on GE during cycling will be studied, with the intent of determining if a heat-induced change in GE could account for the performance decrements in time trialxavierdisley wrote:Gross mechanical efficiency is affected by temperature.
I think you need to brush up on your physiology.
You do realise the difference between checking a static calibration and setting the zero offset (done within sessions)? I think you're just being argumentative for the sake of it
Xav
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2039810/
Only checking static calibration 3 times over a few months really is pathetic and you know it. I'm well aware of the difference between static calibration and setting zero offset.
Frankly anyone who knows anything about power meter accuracy knows damn well if you want to do scientific tests you should use a power meter which is more accurate and repeatable than a Powertap.
Why on earth didn't you use an SRM pro which has proven accuracy to 0.5% instead of Powertap's 1.5%?0 -
The only pathetic thing I can see here isn't related to the study.Stalin wrote:Only checking static calibration 3 times over a few months really is pathetic and you know it.0 -
Alex_Simmons/RST wrote:
The only pathetic thing I can see here isn't related to the study.Stalin wrote:Only checking static calibration 3 times over a few months really is pathetic and you know it.
If you only properly check the accuracy of the power meter 3 times in a few months you run the risk of invalidating every single test since the previous test. This is why the powermeter should be properly checked before and after every test.
Just because the power meter was accurate when tested 3 weeks ago and accurate when tested today does not mean the power meter was accurate every day and every hour in use for 3 weeks.
Powertap is accurate to + / - 1.5%. That is not accurate enough for a scientific study.
Also, if the subjects were hotter when doing their last test compared to their first which they would have been, their efficiency would be affected.0 -
Stalin, you know that moderating staff know that you are yet another incarnation of previous characters banned from the forum for various reasons...
The thread is called "pedalling technique" and your tedious going on is technically trolling... so give it a cut, there is only so much that can be tolerated...
left the forum March 20230
This discussion has been closed.
