Cadence - what is most efficient

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Philinmerthyr
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Cadence - what is most efficient

Postby Philinmerthyr » Sun Sep 30, 2012 19:15 pm

Can someone please give me a lesson on cadence or point me in the direction of a website that will give me the key ponts to think about.

Thanks


Simon Masterson
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Re: Cadence - what is most efficient

Postby Simon Masterson » Sun Sep 30, 2012 20:42 pm

If you want it in a nutshell, spin as fast as you can in the highest gear that you can manage.

Measuring it in numbers (as well as heart rate and power output) is more prescriptive and useful for training purposes, but the above is a good basic premise, and I don't as yet own a computer that measures cadence so can't give comment.

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wilo13
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Re: Cadence - what is most efficient

Postby wilo13 » Sun Sep 30, 2012 22:09 pm

A high cadence is more efficient. To give you an idea most pro's have a cadence in the 85-100 region. Me personally I find 85-90 on the road is good for me and in TT's I am usually around the 95 region.
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coriordan
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Re: Cadence - what is most efficient

Postby coriordan » Sun Sep 30, 2012 23:00 pm

As above. Aim to spin around 90 when seated. (I prefer slightly slower when sprinting up hills)

MichaelW
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Re: Cadence - what is most efficient

Postby MichaelW » Sun Sep 30, 2012 23:19 pm

Any rider has a sustainable power output. You can use this by pedalling with lots of force slowly (high gear) or a little force, rapidly (low gear). It is the same power delivered to the wheels and you go the same speed.
High cadence makes the cardi system do more work, low cadence makes the legs work harder. Pick whatever suits your body type. Most newbies select the wrong cadence, too slow.
Note, to pedal rapidly you need cranks that fit your legs. Smaller cranks can be pedalled more rapidly but each rotation takes less work.
Note the relationship between force, power and work.

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JamesB5446
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Re: Cadence - what is most efficient

Postby JamesB5446 » Mon Oct 01, 2012 06:49 am

Slightly off topic, but I was wondering about power meters. Why are they so expensive?
You can get cheapish electric bikes with torque sensors. Power is a function of torque and rpm so why can't you used one of these torque sensors and a cadence meter to work out your power?

bahzob
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Re: Cadence - what is most efficient

Postby bahzob » Mon Oct 01, 2012 09:31 am

wilo13 wrote:A high cadence is more efficient. To give you an idea most pro's have a cadence in the 85-100 region. Me personally I find 85-90 on the road is good for me and in TT's I am usually around the 95 region.


This is correct but you also need to work on your pedal technique. I have a Wattbike which has allowed me to completely change the way I pedal with some very nice power improvements as a consequence (FTP 300W>325W).

I found simply spinning faster didn't do much by itself. The big improvements came when I concentrated on getting the various muscles involved in pedalling more engaged and working at the best time. When I did this the cadence went up anyway as a consequence.

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Zendog1
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Re: Cadence - what is most efficient

Postby Zendog1 » Mon Oct 01, 2012 17:08 pm

bahzob wrote:
wilo13 wrote:A high cadence is more efficient. To give you an idea most pro's have a cadence in the 85-100 region. Me personally I find 85-90 on the road is good for me and in TT's I am usually around the 95 region.


This is correct.

Wrong! Low cadence is the most efficient in the sense that it uses less fuel / oxygen per mile. The advantage of high cadence is less stress on the legs = (posssibly) less injury.

bahzob
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Re: Cadence - what is most efficient

Postby bahzob » Tue Oct 02, 2012 09:39 am

Zendog1 wrote:
bahzob wrote:
wilo13 wrote:A high cadence is more efficient. To give you an idea most pro's have a cadence in the 85-100 region. Me personally I find 85-90 on the road is good for me and in TT's I am usually around the 95 region.


This is correct.

Wrong! Low cadence is the most efficient in the sense that it uses less fuel / oxygen per mile. The advantage of high cadence is less stress on the legs = (posssibly) less injury.


You are taking a limited definition of efficiency. There is no absolute definition of this, it depends on your objective. So yes if your aim is to cover the maximum distance on flat terrain with the least amount of calories expended pedalling slowly may be more "efficient".

However once you introduce real world factors and speed as an objective this changes. Which is why as per the post above you find that all professional riders have high cadences. The toughness and competition in events like the tour de France acts as a pretty good selection mechanism, if it was more "efficient" for them to pedal slowly you can be assured they would.

There are good reasons for this. You seem to understand this when you say that high cadence produces less stress on the legs. That is correct but the issue is nothing to do with injury. To produce the same power pedalling slowly as fast each pedal revolution has, by definition, got to produce higher average and maximum force. These are accentuated by road conditions (e.g. sudden gradient rises) and, in races, by sudden changes of pace.

The result is that if you look at the force profile of a slow revolution it is more spiky than a fast revolution. This causes more muscle fatigue than a smooth steady effort and this is a bigger limiter in terms of performance and real world efficiency than marginal considerations of energy usage.

You don't need to ride a pro race to see this. It is the reason so many people suck at climbing big mountains. They try to turn over too big a gear at too slow a pace. Their pedalling, literally, becomes a vicious circle. As they get fatigued their cadence slows so the force requirements each rev become bigger so they get more fatigued etc. etc. The effect is amplified by any sudden rise which needs a sprint intensity max effort.Ultimately they fail. If they just chose a gear they could maintain at 70rpm+ (with a couple in reserve for any especially tough sections) they would, by any definition of the term, be more efficient.

bahzob
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Re: Cadence - what is most efficient

Postby bahzob » Tue Oct 02, 2012 12:09 pm

The pictures below illustrate my point. Both show the force applied through a pedal revolution.

The first is while using a slow cadence of sub 70 rpm generating around 320W. The force through the stroke is irregular with a peak of over 450N. (As a side note it also shows that there is more than one definition of efficiency. In this case it is defined as the percentage of a revolution where force is being applied.)

The second shows a higher cadence of 90 rpm and also the result of training to improve pedal stroke. Its pretty clear that the force is far more evenly applied through the stroke just by looking at the curve. The peak is far less at around 300N yet the power is more at 340W. (The "efficiency" is up as well).

The second is way easier to maintain for protracted periods of time, especially at high loads at/above threshold which is why it is more efficient in the practical sense of the word.

Slow cadence, inefficient irregular force
Image


High cadence "efficient" regular force

Image

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kieranb
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Re: Cadence - what is most efficient

Postby kieranb » Tue Oct 02, 2012 15:28 pm

On the flats on my road bike I do about 100rpm, uphill this drops as the slope increases in steepness, until I bottom out on my gears and end up at around 60rpm on steep hills. I find it much harder to spin on my MTB, don't know if this is because the frame geometry is different or due to longer crank lengths?

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mfin
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Re: Cadence - what is most efficient

Postby mfin » Wed Oct 03, 2012 00:17 am

Look up Fast Twitch and Slow Twitch muscles, how they're fuelled etc... that helps when understanding cadences for the same given speed. (you'll then see why a marathon runner is always skinny and a spinter is muscley... same for a TDF GT contender as against Chris Hoy for example).

As a rule, you will find beginners turning over at 50-70 rpm average on a ride, you've got to up that if you're doing it, at least get to 75rpm, and preferably higher, more like 85 or 90 but whatever feels right for you as to how much higher you go, 90rpm would be the higher end of the spectrum for most people. (all averages from a ride).

Thats an oversimplified version.
.

Tom Dean
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Re: Cadence - what is most efficient

Postby Tom Dean » Wed Oct 03, 2012 08:36 am

bahzob wrote:The second is way easier to maintain for protracted periods of time, especially at high loads at/above threshold which is why it is more efficient in the practical sense of the word.
Evidence please.

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markos1963
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Re: Cadence - what is most efficient

Postby markos1963 » Wed Oct 03, 2012 14:44 pm

MichaelW wrote:Note, to pedal rapidly you need cranks that fit your legs. Smaller cranks can be pedalled more rapidly but each rotation takes less work.


Right and wrong. Yes you certainly need crank lengths that suit both your size and fit, this will enable you to spin and produce power at the optimum for your body type.
Wrong that short cranks take less work, don't forget a crank is in effect a lever and the longer a lever the less power is needed to make a turn. Where people get confused is the turning circle, because a longer crank has a bigger turning circle it takes longer to make a revolution leading to the thought it takes more effort.

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JamesB5446
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Re: Cadence - what is most efficient

Postby JamesB5446 » Thu Oct 04, 2012 16:02 pm

markos1963 wrote:
Wrong that short cranks take less work, don't forget a crank is in effect a lever and the longer a lever the less power is needed to make a turn.

Torque, not power. I think?

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markos1963
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Re: Cadence - what is most efficient

Postby markos1963 » Fri Oct 05, 2012 14:12 pm

JamesB5446 wrote:
markos1963 wrote:
Wrong that short cranks take less work, don't forget a crank is in effect a lever and the longer a lever the less power is needed to make a turn.

Torque, not power. I think?


I think I should have used the word 'force' instead to avoid confusion.

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wilo13
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Re: Cadence - what is most efficient

Postby wilo13 » Sat Oct 13, 2012 19:40 pm

bahzob wrote:The pictures below illustrate my point. Both show the force applied through a pedal revolution.

The first is while using a slow cadence of sub 70 rpm generating around 320W. The force through the stroke is irregular with a peak of over 450N. (As a side note it also shows that there is more than one definition of efficiency. In this case it is defined as the percentage of a revolution where force is being applied.)

The second shows a higher cadence of 90 rpm and also the result of training to improve pedal stroke. Its pretty clear that the force is far more evenly applied through the stroke just by looking at the curve. The peak is far less at around 300N yet the power is more at 340W. (The "efficiency" is up as well).

The second is way easier to maintain for protracted periods of time, especially at high loads at/above threshold which is why it is more efficient in the practical sense of the word.

Slow cadence, inefficient irregular force
Image


High cadence "efficient" regular force

Image


Nice to see some quantitative data to back up what we have been saying. Interesting post.
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oldwelshman
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Re: Cadence - what is most efficient

Postby oldwelshman » Sat Oct 13, 2012 23:29 pm

The right direction is forward. People on these forumes focuse much too much on cadence, power meters, pedal technique, crank size,training zones etc There may be marignal gaine for pros but for average Joe public and for 99.9% of people on here all it needs is to ride the bike more often, and harder and you will get better.
As for cadence, fast and slow twicth have nothing at all to do with cadence, more to do with max power putpurt for short bursts or longer endurance efforts.
Ther is no maximum efficiency cadance and it would vary for individuals anyway and more likely to be within a range rather than a specific cadence.

nolight
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Re: Cadence - what is most efficient

Postby nolight » Sun Oct 14, 2012 05:17 am

I am thinking:

Low cadence is better if you are big and powerful like a 100m sprinter.
High cadence is better if you are small and has endurance like a marathon runner.


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