How much force is a bicycle pedal stroke?

Anna C

Level 9 Valued Member
Elite Certified Instructor
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?
 

North Coast Miller

Level 7 Valued Member
This might help. Its going to be all over the place, and when using toe clips it will be spread between feet to varying degrees etc

Bike Calculator

Edit to add:
This doesn't give lbs of resistance per pedal, but you could probably get a rough idea of that by attaching a linear scale (like a fishing one) to the resting down pedal positioned at 9o clock, and apply force on the uphill, 3 o clock pedal till it "feels" about right for an average stroke.
 
Last edited:

Anna C

Level 9 Valued Member
Elite Certified Instructor
This might help. Its going to be all over the place, and when using toe clips it will be spread between feet to varying degrees etc

Bike Calculator

Yes, that's a good one! It says it's 132 watts for my stats, which seems about right for the average effort. But yes, how to then translate that to pounds of force per pedal stroke... ? I like the scale idea, but I don't have one like that.
 

North Coast Miller

Level 7 Valued Member
You could estimate roughly as a % of bodyweight.
Figure an all out effort is bodyweight on one leg - maybe you can increase that by another 20-30lbs by hopping and bracing against the handlebar, but roughly 100% = bodyweight.

Casually pedaling along in a mid gear might not be much more than the weight of your leg which is actually aligned with the pedal, in which case most of the force is provided by raising the leg mass, not pressing it down - although a small amount of that is also helped along by the mass of the opposite leg as it depresses the opposite pedal.

Maybe a good start would be to get a bathroom scale, a stool, and arrange yourself so you get a rough idea of how much your leg mass weighs resting on the pedal, and go from there - X + lbs of effort. Once you have a rough idea of the casual minimum, and BW is the max, you at least have a little science behind the guess.
 

offwidth

Level 9 Valued Member
I don't think knowing the force provides much if any value. Knowing the power on the other had provides insight into the intensity of the training session.

Getting the power value is very simple. Just not cheap. You can get crank and pedal power meters. From there if you really wanted to get an idea of force; it's just math...

That being said there are some light bike components that have ratings as to how much force (weight) they can take.
 

krg

Level 5 Valued Member
Power = work / time = (force x distance) / time

Distance = 2 pi x r (r is length of pedal crank) - circumference of pedal stroke

Time for one pedal stroke you can work out from your cadence.

Probably need to divide by two as the power output will be for both legs.

Just need to measure your cadence and you pedal crank and it's simple maths ;)
 

offwidth

Level 9 Valued Member
Power = work / time = (force x distance) / time

Distance = 2 pi x r (r is length of pedal crank) - circumference of pedal stroke

Time for one pedal stroke you can work out from your cadence.

Probably need to divide by two as the power output will be for both legs.

Just need to measure your cadence and you pedal crank and it's simple maths ;)
Yep... that's the math.
Some power meters are per pedal or crankarm.
 

krg

Level 5 Valued Member
I think if you did the maths you'd find the force is small. You just don't do that much work riding a bike

As Pavel says 'a fat man can ride all day on a bicycle'
 

offwidth

Level 9 Valued Member
Well... force is Newtons right. (Mass x gravitational acceleration)

And with all due respect to Pavel... try riding all day up a steep hill on a mountain bike, or even a steep road climb when you are out of the saddle.

And while the force is going to be relatively small, the amount of work depends upon the distance you are displacing the force. So doing a 2,000m climb on a bike is more than a bit of work...

Just sayin'...
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
Well... force is Newtons right. (Mass x gravitational acceleration)

12 newtons, then? That = 2.7 lbs (pound-force)... seems plausible as an average force for the whole pedal stroke...
 

offwidth

Level 9 Valued Member
Pedal Force
Posted on July 31, 2012by sensiblecycling

Today’s post is going to form the basis for several future articles. We are going to take a look at what kind of forces a rider is likely to exert on the cranks. This has implications across a wide range of topics – from weight training to frame flexion.

We can calculate the force exerted based on a given Power, Cadence and Crank Length. So bring on the physics lesson:

“Work” is measured in Watts, and “Power” (which we often refer to by number of “Watts”) is technically Watts per second. Since Work = Force * Distance, we can substitute Power for Work where we are talking about a one-second duration

(Power = Force * Distance) -> (Force = Power / Distance)

Now distance is equal to Speed * Time. And since Time = 1, then in this case, Distance = Speed (of the pedal). Jumping ahead a bit… Speed = 2 * Pi * Crank Length * Cadence / 60. So if we substitute that back into our original formula:

Force = Power / (2 * Pi * Crank Length * Cadence / 60)

Or… Force = Power * 30 / (Pi * Crank Length * Cadence)

This gives us the average force acting on the pedal for a given power output, cadence and crank length. But note the fact that this is not the peak force. The general consensus within the community (Footnote 1) is that for most riders, peak force (i.e. when the cranks are horizontal) is roughly double the average force. So in the examples below I’ll be calculating average force and doubling it to give peak force. Also, I’ll be converting Force in Newtons to an equivalent Force in kg (using G = 9.8)

To give you an idea of some various situations, I’m going to assume 172.5mm Cranks, a cadence of 85 and a 70kg rider. Why am I mentioning the weight? Well, based on average power/weight ratios, we’re going to convert the rider’s weight into a power figure depending on his level (Footnote 2)

A Grade Rider
Time Trial – 348 Watts: 46kg
Pushing Hard (5min) – 416 Watts: 55kg
Full Bore Sprint – 1378 Watts: 183kg

E Grade Rider
Time Trial – 193 Watts: 26kg
Pushing Hard (5min) – 235 Watts: 31kg
Full Bore Sprint – 902 Watts: 120kg

Things to Note:

Even when you’re riding hard over a short-ish distance, the force required per pedal stroke is quite low. In comparison to the maximum force your muscles are capable of producing, you’re not asking very much. This has a bearing on the efficacy of weight training for cyclists.

The difference between a full bore sprint and “pushing hard” is massive. When talking about how “stiff” a bicycle is, it’s worth taking this into consideration

The above figures are not affected by gear ratio or whether it’s uphill or downhill. The only important factors are Power and Cadence.
 

offwidth

Level 9 Valued Member
With all that said, I'll reiterate... I don't think force is really that important other than in selecting components for their strength, and as the article above alluded to, in frame design.

Power however is a metric worth measuring for serious and competitive cyclists.
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
With all that said, I'll reiterate... I don't think force is really that important other than in selecting components for their strength, and as the article above alluded to, in frame design.

Power however is a metric worth measuring for serious and competitive cyclists.

Agreed... not wanting to know as a training variable, but mainly to illustrate the enormous gap between low-to-moderate force production (but not trivial -- at least a few pounds) that one could do literally 10,000 times in an exercise session, vs. the high end of strength -- which is still only 80% or so of max force production that one can do maybe 50 times in an exercise session.

So my questionable calculation comes up with 2.7 lbs for the whole pedal stroke, but let's condense it to 25% of the pedal stroke and call it 10.8 lbs. That seems plausible to me for the peak force for my 18 mph average speed on flat ground.

So I can produce 10.8 lbs of force 9,450 times on a bike ride for 102,060 pounds of force production, and 150-300 lbs of force (let's average to 200 lbs) to squat and deadlift 50x in a session for 10,000 pounds of force production. Maybe not accurate or valid for anything, but interesting to think about.
 

North Coast Miller

Level 7 Valued Member
IDK... When I'm pedaling with intent on my mountain bike, using road tires, I'd bet I'm exerting close to 10lbs just on the upstroke with the other leg.
Figure a lot of the force is provided by limb weight and swaying over the working leg, I'd imagine a moderate effort for my 185lbs is closer to 20lbs of peak down pressure, at a guess...
 

Anna C

Level 9 Valued Member
Elite Certified Instructor
IDK... When I'm pedaling with intent on my mountain bike, using road tires, I'd bet I'm exerting close to 10lbs just on the upstroke with the other leg.
Figure a lot of the force is provided by limb weight and swaying over the working leg, I'd imagine a moderate effort for my 185lbs is closer to 20lbs of peak down pressure, at a guess...

Yes, that sounds about right to me... though I'm not sure which variables would account for the difference.

I would guess overall that the peak force of my pedal stroke varies from 5 to 50 lbs... maybe greater in a sprint.
 
Top Bottom