Efficiency

Herbsman

I read that while cycling we are on average about 25% efficient. I take that to mean that, for example, I burn 1 kilojoule per second when pushing 250 watts through the pedals. Is this correct?

amaferanga

I guess you want to know how many calories you burn based on a kJ figure? If so then 1 kJ is approximately equivalent to 1kCal. So if you ride at around 270W for an hour then you'll burn approximately 1000kCal (probably a bit more).

Alex_Simmons/RST

Herbsman wrote:

I read that while cycling we are on average about 25% efficient. I take that to mean that, for example, I burn 1 kilojoule per second when pushing 250 watts through the pedals. Is this correct?

Most cyclists are in the range of 18%-24%, meaning that for every kJ metabolised while cycling, approximately 20% of that gets to the cranks. The rest is mostly waste heat.

your numbers are close, but 25% would be an unusually high efficiency level.

Herbsman

amaferanga wrote:

I guess you want to know how many calories you burn based on a kJ figure? If so then 1 kJ is approximately equivalent to 1kCal. So if you ride at around 270W for an hour then you'll burn approximately 1000kCal (probably a bit more).

I basically want to do a presentation to the guys at work who moan about how much I eat!

RowCycle

I've often wondered why we don't do more pedalling technique work, in other sports a lot of time and effort goes into honing the technique, to increase efficiency, but in cycling most people I've spoke to don't consider it - say the way they cycle is the way it is, rather than trying to improve it.

Anyone got any link of how to increase effeciency / what the correct technique for pedaling should be?

(now expects stupid comments)

themogulman

Get a bike fit is the best idea no matter of fiddling will match this.

Also work on pedalling with one leg at the start of rides/turbo sessions.30 each side to "switch" those muscles on.

Alex_Simmons/RST

RowCycle wrote:

I've often wondered why we don't do more pedalling technique work, in other sports a lot of time and effort goes into honing the technique, to increase efficiency, but in cycling most people I've spoke to don't consider it - say the way they cycle is the way it is, rather than trying to improve it.

Anyone got any link of how to increase effeciency / what the correct technique for pedaling should be?

(now expects stupid comments)

The reason is that we are locked into a pedal and the range of motion (degrees of freedom) is extremely limited in cycling. Cycling is a very low technique sport (relative to other sports). In other aerobic endurance sports (e.g. swimming, rowing, running) there are far greater freedoms of motion requiring neuromuscular control, hence technique plays a much greater role in those sports, and so more time needs to be devoted to technique.

Efficiency (beyond going from never riding to a regular club Joe/Josephine) is, by and large, an inherited trait. If one can change efficiency, it is through huge volumes of riding over many years (e.g. a professional rider), and the mechanism is most probably due to changes in the balance of muscle fibre type caused by such high volume training (Type I is more efficient than Types II a/b/x).

Consider that, on average, Professional riders are no more or less efficient that regular club riders, and you'll get an appreciation of how little one can influence efficiency. Nevertheless, chronic changes in efficiency may occur (it is actually quite hard to get solid information as such large longitudinal studies are not available AFAIK). There are of course many things that can have an acute impact to efficiency.

The most important thing you can do (apart from training) is to get a good bike fit.

Finally, focus on sustainable power output as that's what matters. Efficiency per se isn't that important.

Herbsman

RowCycle wrote:

I've often wondered why we don't do more pedalling technique work, in other sports a lot of time and effort goes into honing the technique, to increase efficiency, but in cycling most people I've spoke to don't consider it - say the way they cycle is the way it is, rather than trying to improve it.

Anyone got any link of how to increase effeciency / what the correct technique for pedaling should be?

(now expects stupid comments)

Have a look at the pdf that Alex Simmons posted on the Wattbike thread in the Training forum

A study found that the most metabolically efficient way to pedal was actually whatever the rider's preferred method of pedaling is (as opposed, for example, to pedaling in circles or pulling up on the back pedal).

bahzob

Herbsman wrote:

RowCycle wrote:

I've often wondered why we don't do more pedalling technique work, in other sports a lot of time and effort goes into honing the technique, to increase efficiency, but in cycling most people I've spoke to don't consider it - say the way they cycle is the way it is, rather than trying to improve it.

Anyone got any link of how to increase effeciency / what the correct technique for pedaling should be?

(now expects stupid comments)

Have a look at the pdf that Alex Simmons posted on the Wattbike thread in the Training forum

A study found that the most metabolically efficient way to pedal was actually whatever the rider's preferred method of pedaling is (as opposed, for example, to pedaling in circles or pulling up on the back pedal).

Rubbish. Look at video of professional cyclist. Then look at a video of the average cyclist. They pedal in completely different ways, the difference is often as big as comparing the swings of professional golfer and a golfing hack.

The notion that these amateur cyclists are incapable of improving their their efficiency is utterly bizarre. The more so since extremely good cyclists have improved by changing theirs.

The main issue with improving efficiency is that it can be difficult to measure and assess, especially on-road. This will change and eventually it will be to measure/display pedaling efficiency real-time. (http://www.factorbikes.com/astonmartin/ ... tions.html the shape of things to come)

When this happens coaches will start to write articles on how to improve and this forum will start to have more informed threads on this topic.

amaferanga

bahzob wrote:

Herbsman wrote:

RowCycle wrote:

I've often wondered why we don't do more pedalling technique work, in other sports a lot of time and effort goes into honing the technique, to increase efficiency, but in cycling most people I've spoke to don't consider it - say the way they cycle is the way it is, rather than trying to improve it.

Anyone got any link of how to increase effeciency / what the correct technique for pedaling should be?

(now expects stupid comments)

Have a look at the pdf that Alex Simmons posted on the Wattbike thread in the Training forum

A study found that the most metabolically efficient way to pedal was actually whatever the rider's preferred method of pedaling is (as opposed, for example, to pedaling in circles or pulling up on the back pedal).

Rubbish. Look at video of professional cyclist. Then look at a video of the average cyclist. They pedal in completely different ways, the difference is often as big as comparing the swings of professional golfer and a golfing hack.

The notion that these amateur cyclists are incapable of improving their their efficiency is utterly bizarre. The more so since extremely good cyclists have improved by changing theirs.

The main issue with improving efficiency is that it can be difficult to measure and assess, especially on-road. This will change and eventually it will be to measure/display pedaling efficiency real-time. (http://www.factorbikes.com/astonmartin/ ... tions.html the shape of things to come)

When this happens coaches will start to write articles on how to improve and this forum will start to have more informed threads on this topic.

Any cyclist in particular? Because no two will pedal in exactly the same way, yet you seem yo be suggesting that there's some 'optimum' way that everyone should pedal....

Alex_Simmons/RST

bahzob wrote:

Rubbish. Look at video of professional cyclist. Then look at a video of the average cyclist. They pedal in completely different ways, the difference is often as big as comparing the swings of professional golfer and a golfing hack.

The notion that these amateur cyclists are incapable of improving their their efficiency is utterly bizarre. The more so since extremely good cyclists have improved by changing theirs.

The main issue with improving efficiency is that it can be difficult to measure and assess, especially on-road. This will change and eventually it will be to measure/display pedaling efficiency real-time. (http://www.factorbikes.com/astonmartin/ ... tions.html the shape of things to come)

When this happens coaches will start to write articles on how to improve and this forum will start to have more informed threads on this topic.

We can already have quite well informed discussion on efficiency, but it helps if people actually understand what efficiency is. Such a bike as linked will do nothing of the sort to improve our understanding.

The only way to measure efficiency is by measuring the rate of energy metabolised (which requires gas exchange analysis using a metabolic cart) and the power getting to the cranks. Even then the metabolic measurement is subject to much error.

Just because a cyclist produces more power (or has improved their power output), does not mean they are more efficient. Indeed that is the least likely thing to have happened.

bahzob

amaferanga wrote:

Any cyclist in particular? Because no two will pedal in exactly the same way, yet you seem yo be suggesting that there's some 'optimum' way that everyone should pedal....

Well sorry if I didn't make myself clear. I actually agree absolutely that no two people will necessarily pedal the same way. They will differ for all sorts of reasons, that indeed is part of my point.

However the way they pedal right now is not, as Alex is saying, innately optimal. With the right feedback I believe they can improve it.

bahzob

Alex_Simmons/RST wrote:

We can already have quite well informed discussion on efficiency, but it helps if people actually understand what efficiency is. Such a bike as linked will do nothing of the sort to improve our understanding.

The only way to measure efficiency is by measuring the rate of energy metabolised (which requires gas exchange analysis using a metabolic cart) and the power getting to the cranks. Even then the metabolic measurement is subject to much error.

Just because a cyclist produces more power (or has improved their power output), does not mean they are more efficient. Indeed that is the least likely thing to have happened.

For the purposes of this argument it is not necessary to measure anyone's metabolic rate, bearing in mind that efficiency as discussed here is simply a case of actual performance/ideal performance.

A thought experiment is enough.

Image we have someone, say "Fred", who we have seen is capable of 300W FTP (in its actual sense so he can sustain a steady 300W for 60 minutes.)

> Everyone, I think, will agree that if we put Fred on a bike he will not produce 300W if his bike is not correctly set up. So he will be more "efficient" with proper set up.

> Say his bike is set up correctly. Now we ask Fred to pedal but tell him he can only push down on the pedals when they are near vertical. We would not expect him to produce 300W, no matter how hard he tried. So "efficiency" does depend on pedaling, even though this is a trivial example.

> The issue is what happens if we ask him simply to pedal as he likes and he does, as expected hold 300W for 60 minutes.

>> Your view, I think, is that assuming all other factors remain constant Fred will not be capable of increasing this power or holding it longer by changing his pedaling technique.

>> My view is that Fred could increase either the 300W or the time he can hold it if he is provided with the appropriate feedback on his pedaling technique. My view is also that the likelihood of this happening and the extent of the improvement will depend on Fred's cycling experience, since an experienced cyclist will have learned the a better technique through trial and error. Further it's also likely that he can use this feedback to refine his bike setup and get further improvement.

My advice to others is to try and use something like a Wattbike or similar piece of kit that gives a graphical view of how you are pedaling. If Alex is right and I am wrong then you won't lose anything but if I am right you may learn something useful. (I did which is why I happen to think Alex is wrong about this.)

Herbsman

Efficiency = work out / work in.

How do you expect to measure efficiency then, without measuring metabolic rate?

I think you are confusing efficiency with something else

Herbsman

So regarding the food I need to eat.

If I ride at 250 Watts for an hour, that is 250J/s . Which is 250 x 60 x 60 = 900 000J.

If I'm 20% efficient it takes me 5 Joules to produce 1 Joule of pedal power, which means for that hour I used 5 x 900 000J = 4 500 000. 4.5MJ! That's about 1076 kCal, equivalent to about 286 grams of sugar. Is that right?! :shock:

Herbsman

Do I need to eat about three of these meals just to ride for an hour?!

Herbsman

Herbsman wrote:

So regarding the food I need to eat.

If I ride at 250 Watts for an hour, that is 250J/s . Which is 250 x 60 x 60 = 900 000J.

If I'm 20% efficient it takes me 5 Joules to produce 1 Joule of pedal power, which means for that hour I used 5 x 900 000J = 4 500 000. 4.5MJ! That's about 1076 kCal, equivalent to about 286 grams of sugar. Is that right?! :shock:

Anybody?

amaferanga

Herbsman wrote:

Herbsman wrote:

So regarding the food I need to eat.

If I ride at 250 Watts for an hour, that is 250J/s . Which is 250 x 60 x 60 = 900 000J.

If I'm 20% efficient it takes me 5 Joules to produce 1 Joule of pedal power, which means for that hour I used 5 x 900 000J = 4 500 000. 4.5MJ! That's about 1076 kCal, equivalent to about 286 grams of sugar. Is that right?! :shock:

Anybody?

Apart from 20% efficiency being a bit low that sounds about right. I always assume 25% efficiency so as not to overestimate calories burnt so that gives 1000kCal/hour @ ~270W.

Alex_Simmons/RST

You will be limited by the rate at which you can digest/absorb carbs. How much energy you have metabolised in total is really only of interest when considering total energy intake requirements for the entire day.

You *might* manage to absorb up to 1g (maybe 1.5g) of CHO per kg of body mass per hour, but everyone is different and learning to eat during exercise is a practice drill in itself. Too much and you will probably suffer gastro problems, and/or be forced to slow down.

IOW, when riding hard, you can't replenish glycogen stores at the same rate you are using them (at 250W, you might be lucky to replenish a quarter of that while riding but most likely somewhat less). We simply can't absorb the nutrients fast enough.

Herbsman

Now I want a power meter just out of curiosity for how much energy is coming out of my legs, not to improve training quality. Anyone got one I can borrow?

Alex_Simmons/RST

This video interview of Asker Jeukendrup is specifically about CHO ingestion and performance:

http://www.youtube.com/watch?NR=1&v=yZD ... =endscreen

adm1

Herbsman wrote:

Now I want a power meter just out of curiosity for how much energy is coming out of my legs, not to improve training quality. Anyone got one I can borrow?

You can rent a Wattbike on a per month basis....that's what I did over the last winter. It was very useful and interesting. Damn good indoor training bike too.

P_Tucker

adm1 wrote:

Herbsman wrote:

Now I want a power meter just out of curiosity for how much energy is coming out of my legs, not to improve training quality. Anyone got one I can borrow?

You can rent a Wattbike on a per month basis....that's what I did over the last winter. It was very useful and interesting. Damn good indoor training bike too.

You can rent powermeters too.

technique

Alex_Simmons/RST wrote:

The reason is that we are locked into a pedal and the range of motion (degrees of freedom) is extremely limited in cycling. Cycling is a very low technique sport (relative to other sports). In other aerobic endurance sports (e.g. swimming, rowing, running) there are far greater freedoms of motion requiring neuromuscular control, hence technique plays a much greater role in those sports, and so more time needs to be devoted to technique.

Efficiency (beyond going from never riding to a regular club Joe/Josephine) is, by and large, an inherited trait. If one can change efficiency, it is through huge volumes of riding over many years (e.g. a professional rider), and the mechanism is most probably due to changes in the balance of muscle fibre type caused by such high volume training (Type I is more efficient than Types II a/b/x).

Consider that, on average, Professional riders are no more or less efficient that regular club riders, and you'll get an appreciation of how little one can influence efficiency. Nevertheless, chronic changes in efficiency may occur (it is actually quite hard to get solid information as such large longitudinal studies are not available AFAIK). There are of course many things that can have an acute impact to efficiency.

The most important thing you can do (apart from training) is to get a good bike fit.

Finally, focus on sustainable power output as that's what matters. Efficiency per se isn't that important.

How wrong can you be. Efficiency is not important in sprinting etc but for sustainable max power output in TT's it is all important. Why has the dead spot sector (11- 1 o'c) always been accepted as a permanent fixture in the pedaling circle when it could easily be replaced with maximal crank torque. Reduced torque between 1-2 o'c can also be increased to maximal torque, saving much wasted pedal force on each pedal stroke. Yes it is me Alex.

Alex_Simmons/RST

technique wrote:

Yes it is me Alex.

Then I won't be expecting any sensible discussion relating to actual performance then.

DaveyL

Honest question - I've often wondered about something similar. Obviosuly it's not "efficiency" as defined by exercise physiologists, but is the poster getting at something I might call "neuromuscular efficiency"?

E.g. I can hold 300 Watts for an hour on my road bike. I get onto my new TT bike, and all of a sudden 300 Watts feels much harder to hold (or it could be on my mountain bike - less of an extreme change of position). At one extreme, I might not be able to hold 300 Watts for the hour, or I might be able to do it but my HR is much higher compared to the same Wattage on the road bike. But over time, I "get used" to the different position and can output the same Watts as on my road bike, for the same HR.

Q: Has anyone tried to measure this difference in "efficiency" in the lab, at the same intensity and in different positions? Would you burn the same number of calories? If not, then cycling "efficiency" is not just the physiologically defined "gross muscular efficiency" but there is another component to it, based on how neuromuscularly "comfortable" (for want of a better term) you are with the positon. Thoughts? Apologies if this is a load of rambling nonsense but I have often wondered about it.

Alex_Simmons/RST

Yes, it's been a subject of studies for decades, in particular since "aerobars" became more common.
Some examples:
http://www.ncbi.nlm.nih.gov/pubmed/1956270
http://www.ncbi.nlm.nih.gov/pubmed/8664843
http://www.ncbi.nlm.nih.gov/pubmed/9219211
http://www.ncbi.nlm.nih.gov/pubmed/8492689
http://www.ncbi.nlm.nih.gov/pubmed/9721057
http://www.ncbi.nlm.nih.gov/pubmed/14514538

I'm sure there are others.

As for my thoughts - well you work on what provides the best performance outcome. Efficiency (within reasonable limits) is really only a consideration in ultra endurance events.

For shorter races (like most road races, time trials and shorter) then it's sustainable power to weight and sustainable power to aero drag ratios that matter most.

DaveyL

Cheers, Alex. Plenty of bedtime reading there

I guess if anything it just emphasises the principle of specificity.