Howie

Hi all,

I am currently researching into different ways to measure the calories burned by a cyclist during a ride. Looking at the ride specifically (i.e. not taking into account factors such as age, lean body mass etc.), I have considered calories as energy and consequently the energy expended by the rider would be based on the force the rider applies during the ride multiplyed by the speed at which they are cycling at. In regards to different ways of measuring the force expended by the rider, one way that I have found would be to use a strain gauge on either side of the pedal. Does anyone have any suggestions as to where on the bicycle the best place would be to measure the force applied by the rider, and also other ways of determining the force applied by the rider? Any suggestions would be greatly appreciated. Many thanks.

powers2b

F=ma.
Weigh the bike and rider.
Measure distance and acceleration with a cycle computer.
Calculate force.
Simple

ofofhy

Yes, but that doesn't account for overcoming friction, as a cyclist maintaining a constant speed must still exert force on the pedals.

Maybe 3-D accelerometers on the pedals or shoes. That would give you the actual acceleration of the pedal itself, then the mass of the rider, assuming all his/her weight is on one pedal at a time (completely out of the saddle and really pumping) would give the Force applied.

The maximum force should be applied during the downward motion, moving CCW from 9:00 to 6:00. I would use your vertical acceleration at 9:00 as a in F=ma.

ofofhy

If you are maintaining speed, you are not accelerating. You are exerting a force to overcome the friciton of the drivetrain/bearings/road.

powers2b

The forces of friction and wind resistance can be calculated when the rider stops pedaling. By measuring the deceleration you get the force (mass is constant).
Not all engineering problems require engineering tools.

ofofhy

The cycle computer: engineering tool? Or is it a bikng tool?

The school probably has a few accelerometers around (assuming that this question is related to a university class - students seem to come here with those at the beginning of semesters) versus buying a cyclocomputer.

Drivetrain friction is not accounted for by measuring decelleration after pedalling stops.

AndrewP

This has already been done. It is a special rear hub with a strain guage between the cassette and the hub that measures the torque being applied to the rear wheel. The power is torque multiplied by rotational speed. There was a thread on this or the road forum recently titled "What is this" (the rear hub on a used bike he had bought).

powers2b

Assumed negligable.

ofofhy

Always state your assumptions.

https://www.sdearthtimes.com/et1199/et1199s13.html

bostontrevor

There's also a system that measures based on deformation in the cranks.

You should check out the book Bicycling Science as it goes into the question of human power generation and output in considerable depth, including the various many ways this is measured.

boyze

You would need a force gage like the rear hub idea or strain gages on the pedals. Even with this, all you would get is the energy needed to propel the bike and rider. It doesn't factor in the inefficiency of the human engine to give total calories expended. Lots of energy goes into biomechanic inefficiencies, keeping cool or warm ........... that would not be accounted for.

darkmother

You guys are talking about mechanical work done, not nessasarily the energy consumed. Naturally this is relevant, but it doesn't tell the whole story. For example, push as hard as you can against a rigid wall. You will quickly tire. From the vantage point of your muscles, you are doing aerobic and anerobic work, but external to your body, no work is done. This is becuase in this instance, the efficiency is zero. Difficult to estimate the actual caloric expenditure of cycling, unless you can estimate, or better still, measure efficiency. Just something to consider. I will be interested to see what you decide to do.

ivan_yulaev

Just found this:

https://www.kreuzotter.de/english/espeed.htm

boyze

There maybe studies done on human efficiencies but a crude way to measure total cycling efficiency is to use the load cell approach on the pedals or hub and that force times its rotation is the work done to propel the bike and rider. Monitor this 4-6 weeks and tally the total energy expended by riding in calories. Concurrent with this do detailed calorie counting on the consumed food and add up the total consumed food calories during the same period. Also keep tract of body weight. For every pound lost or gained add or substract 3500 calories. Now factor in the resting metabolic consumption which is what one burns in calories just getting through the day with non riding activities. There are tables for these numbers based on body weight and activity level. At the end of the several week period do the summation and take the ratio and you should get an efficiency number. Remember all calories mentioned above are actually kilocalories. Crude at best but should give a ballpark number. I'm guessing less than a 50% number for the human engine.

bostontrevor

Have I mentioned Bicycling Science?

531Aussie

https://www.analyticcycling.com/ForcesPower_Page.html

There's also this one, but I don't think it's as elaborate

MichaelW

SRM power cranks are the standard tool used by pro riders to measure their power output.