How much force is a bicycle pedal stroke?

Anna C

Level 9 Valued Member
Elite Certified Instructor
As Pavel says 'a fat man can ride all day on a bicycle'
I think it was Dan John. S&S page 57, "The swing is inefficient, which is why it is a great fat burner," explains Dan John. "The bike is efficient -- and fat people can ride it forever."

I agree with @offwidth though. Not very meaningful. The bike is plenty of work no matter what you weigh. It all depends on how far and how fast you go.
 

mprevost

Level 6 Valued Member
My training lately has consisted of barbell lifts + bike rides. So last week I got to thinking about force production....

In a barbell session, including the warm-up sets, I might do 30-40 squats and 10-15 deadlifts. That's about 50 reps of force production.

On a 31 mile bike ride at 18 mph avg speed, I average 105 total riding minutes and 90 rpm average cadence. That's 9,450 reps of force production.

And a pedal stroke isn't always light --- it can be significant force production at times. So I got to wondering, how many pounds of force is a bicycle pedal stroke, approximately? I know it depends on how evenly force is applied in the pedal stroke, but seems like we could come up with a rough estimate to equate to something like a leg press. My googling didn't come up with any good answers so I thought I would ask here. Does anyone know, or have any guesses?
It is less force than walking up stairs. You can convert from kilogram meters per second to watts here: Convert kg-m/s to watt - Conversion of Measurement Units

At 18 mph you are probably averaging less than 200 watts (probably 150-170). So 15 kg.m per second is 147 watts, which is probably close. That means that if you are averageing 60 rpm (to make the math easier), then you are producing enough force to move 15 kg a distance of 1 meter vertically in one second. Approximately.
 

mprevost

Level 6 Valued Member
I think it was Dan John. S&S page 57, "The swing is inefficient, which is why it is a great fat burner," explains Dan John. "The bike is efficient -- and fat people can ride it forever."

I agree with @offwidth though. Not very meaningful. The bike is plenty of work no matter what you weigh. It all depends on how far and how fast you go.
The bike is about 18-22% efficient. Which is actually pretty efficient for human movement. Swimming and running are significantly worse, and much more variable.
 
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North Coast Miller

Level 7 Valued Member
And what you climb...
This is key. If you're on a grade and literally standing on the pedals while pulling down on the grips to keep those pedals going you are exerting more than your bodyweight.

I have a tough time figuring this out - you would have to go by grade/by gear/by bodyweight/by mechanical efficiency of the bike and tires.
 

offwidth

Level 9 Valued Member
This is key. If you're on a grade and literally standing on the pedals while pulling down on the grips to keep those pedals going you are exerting more than your bodyweight.

I have a tough time figuring this out - you would have to go by grade/by gear/by bodyweight/by mechanical efficiency of the bike and tires.
Hence the expensive power meters....
 

krg

Level 5 Valued Member
What a fun thread.

@Anna C is no slouch and she is cycling at 132 watts = 132 J/s - over the course of an hour she is using 475,200 Joules.

That is 113 kcal. She'll probably use more calories just staying alive for that hour.

Cycling is great - it's fun, you get to zoom around outside. It is woeful as a means of exercise if your aim is to burn calories. There are plenty of studies which show it has great cardiovascular benefits though.

The bicycle is an awesome piece of engineering - it converts really modest forces into really significant forward motion. And the forces really are modest - if you take balance out of the equation and look at trikes then just about everyone from tiny kids to really frail old folk can exert enough force to go.

@offwidth - yes a 2000 m hill climb is a huge effort - I struggle to find anywhere near me that is >50 m above sea level.

@North Coast Miller - I would be surprised if your up stroke is as forceful as you think - try sitting on a stool, hooking your foot through a KB handle nd lifting your leg - it's tough, even for a small bell. There is not that much strength in those muscles. Another fun experiment would be to cycle using only one leg (I'd try it myself but I don't have pedals with clips) as you should be able to maintain Anna like speeds.

If you do try it - please don't fall off - or if you do fall off, please don't blame me ;).
 

offwidth

Level 9 Valued Member
Speed and hills make a huge difference.

Speed because resistance varies as a cube of the speed.

Hills because of gravity.

I ride with some big guys that are pretty hard to touch on the flats; unless you get right on their wheel. But get them on any significant steep climbs, and it's like they have thrown out an anchor...
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
That is 113 kcal. She'll probably use more calories just staying alive for that hour.

Cycling is great - it's fun, you get to zoom around outside. It is woeful as a means of exercise if your aim is to burn calories. There are plenty of studies which show it has great cardiovascular benefits though.
Someone forgot to tell Garmin. It says I burned 1,829 calories! Don't worry, I don't believe it. But I would estimate 300-400 more than being sedentary for that same time.

upload_2019-2-9_16-49-38.png
 

krg

Level 5 Valued Member
Speed and hills make a huge difference.

Speed because resistance varies as a cube of the speed.

Hills because of gravity.

I ride with some big guys that are pretty hard to touch on the flats; unless you get right on their wheel. But get them on any significant steep climbs, and it's like they have thrown out an anchor...
Hence the 15 kg difference in bodyweight between Djamolidine Abdoujaparov (surely the maddest sprinter ever) and Marco Pantani even though they were the same height.
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
The bike is about 18-22% efficient. Which is actually pretty efficient for human movement. Swimming and running are significantly worse, and much more variable.
I've never understood this concept of "efficiency." Could I not run for an hour and cycle for an hour and somehow (by adjusting my pace) put out the exact same amount of energy for both activities? Therefore, what does efficiency refer to?

As for more variable, I have always experienced my bike rides as a much more variable effort as compared to my runs. When I run my HR is a pretty constant line, whereas when I ride a bike it varies all over the place. But I'm probably not getting what variability you're referring to there.
 

offwidth

Level 9 Valued Member
I've also heard that a bicycle is more efficient than a salmon....
Figure that one out...
 

Oscar

Level 6 Valued Member
I think a good measure is when you are going uphill standing up on the pedals. In those cases, I'd say most the bodyweight is on the forward pedal. Then, when pedaling at a normal pace, it would be a fraction of that, maybe 30% or so?
 

North Coast Miller

Level 7 Valued Member
@North Coast Miller - I would be surprised if your up stroke is as forceful as you think - try sitting on a stool, hooking your foot through a KB handle nd lifting your leg - it's tough, even for a small bell. There is not that much strength in those muscles. Another fun experiment would be to cycle using only one leg (I'd try it myself but I don't have pedals with clips) as you should be able to maintain Anna like speeds.
I eventually took my clips off as I was riding less and less and for shorter distances. But there is a huge difference in power output with and without.

Part of that is the clip captures a lot of the push at the top of the stroke and at the very bottom.
When heavily fatigued, using the other leg to pull can give the working leg enough help to keep going.

I don't have the competitive experience a lot of other forum members have, but did a ton of rec and commute riding right up to my early 30s.
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
I think a good measure is when you are going uphill standing up on the pedals. In those cases, I'd say most the bodyweight is on the forward pedal. Then, when pedaling at a normal pace, it would be a fraction of that, maybe 30% or so?
Yes, standing is a different thing too... your bodyweight is producing force with gravity (as it is with a sitting pedal stroke, though for a much smaller amount), PLUS you are producing force into it by pulling on the handlebars to push the pedal away.

I agree, 30% of so of bodyweight is within the range, though not at a cruising fast cadence of 90 rpm.

Here is me in normal cycling mode... I've owned my bike for 10 yrs now; a 2008 Trek Madone, ridden > 18,000 miles.

upload_2019-2-9_19-41-53.png

Part of that is the clip captures a lot of the push at the top of the stroke and at the very bottom.
When heavily fatigued, using the other leg to pull can give the working leg enough help to keep going.
Yes, clips are great for increasing the pedal stroke efficiency. I try to even out the force around the revolution rather than "mashing" the pedal at the top quartile, however there's always going to be more force there, so I thought it would help for illustrative purposes (in my earlier post to calculate total force production) to condense it.

One cycling coach I knew years ago advised unclipping one leg when riding rollers for a minute each side to help even out the pedal stroke. I did do it for a while. He could actually ride rollers, with only one foot clipped in, with no hands!
 

mprevost

Level 6 Valued Member
I've never understood this concept of "efficiency." Could I not run for an hour and cycle for an hour and somehow (by adjusting my pace) put out the exact same amount of energy for both activities? Therefore, what does efficiency refer to?

As for more variable, I have always experienced my bike rides as a much more variable effort as compared to my runs. When I run my HR is a pretty constant line, whereas when I ride a bike it varies all over the place. But I'm probably not getting what variability you're referring to there.
Efficiency is just energy expended/work completed. We can measure your calorie expenditure while cycling and also measure your power output and therefore your total work. If we convert calories to joules and total work to joules, we can simply divide total work/total calories. We get about 20%. This is harder to do for running but it is considered to be less efficient.
 

mprevost

Level 6 Valued Member
I've never understood this concept of "efficiency." Could I not run for an hour and cycle for an hour and somehow (by adjusting my pace) put out the exact same amount of energy for both activities? Therefore, what does efficiency refer to?

As for more variable, I have always experienced my bike rides as a much more variable effort as compared to my runs. When I run my HR is a pretty constant line, whereas when I ride a bike it varies all over the place. But I'm probably not getting what variability you're referring to there.
Yes, power output varies wildly while cycling. I used to see this when I trained with a power meter. But that is not efficiency. That is just power output variability. THe variability I am talking about with running is the difference in energy expenditure between two people. Take two people, both of whom weigh 150lbs, and have them both run at 8 mph. The difference in energy expenditure between the two could be as high as 30%. With cycling, the difference would not get much higher than 5%.
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
Efficiency is just energy expended/work completed. We can measure your calorie expenditure while cycling and also measure your power output and therefore your total work. If we convert calories to joules and total work to joules, we can simply divide total work/total calories. We get about 20%. This is harder to do for running but it is considered to be less efficient.
Ah.... OK that makes sense. So with cycling, more of the work goes directly to making you go, whereas in running it might be moving the arms, bobbing up and down, etc.

Yes, power output varies wildly while cycling. I used to see this when I trained with a power meter. But that is not efficiency. That is just power output variability. THe variability I am talking about with running is the difference in energy expenditure between two people. Take two people, both of whom weigh 150lbs, and have them both run at 8 mph. The difference in energy expenditure between the two could be as high as 30%. With cycling, the difference would not get much higher than 5%.
Also makes sense. Sounds like this is the efficiency that increases in runners as their tissues become more adapted to running, so an experienced runner of the same bodyweight puts out less work to go the same distance. And this doesn't apply so much in cycling.

Thanks, Mike!

So, a follow-up question... If I run for an hour with my HR at 140, and cycle for an hour with my HR at 140, have I likely done the same amount of work and/or burned the same amount of calories?
 
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