Saving calories with Di2 vs. mechanical

[tv_vt]

I rode a century Saturday with a Di2-equipped bike. Was riding the next evening with my wife and happened to see her twist her left hand as she shifted into the big ring.

Later I commented that I might get her a Di2 setup and mentioned that I must've saved a ton of calories using Di2 instead of mechanical shifters over the course of the 100 mile ride.
Let's say I shifted 1000 times (10 times per mile - that's possible given how rolling the course was - maybe it was even more, don't know). The simple press of a single finger versus way more force needed for mechanical shifters had me thinking I saved at a minimum a few hundred calories.

But who knows. Any thoughts on this? Any real studies? I know pros choose to use mechanical for courses like P-R, but most often are using electronic shifting. Do they know something we don't?

[CunegoFan]

Originally Posted by tv_vt

I rode a century Saturday with a Di2-equipped bike. Was riding the next evening with my wife and happened to see her twist her left hand as she shifted into the big ring.

Later I commented that I might get her a Di2 setup and mentioned that I must've saved a ton of calories using Di2 instead of mechanical shifters over the course of the 100 mile ride.
Let's say I shifted 1000 times (10 times per mile - that's possible given how rolling the course was - maybe it was even more, don't know). The simple press of a single finger versus way more force needed for mechanical shifters had me thinking I saved at a minimum a few hundred calories.

If you can burn a few hundred calories by moving your fingers then computer games must be the greatest exercise known to man.

[abr5]

Some really quick math on it... Assuming the throw of the shifter is 50mm and it takes 50N, that's 2.5 joules per shift, so 2.5kj for your 1000 shifts. 1kj=.239 Calories, so .6 Calories total. Maybe that ends up being 2-3 Calories burned by the body with metabolic efficiency.

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[El Chaba]

Originally Posted by CunegoFan

If you can burn a few hundred calories by moving your fingers then computer games must be the greatest exercise known to man.

LOL...I was just thinking that you could also lose weight by reaching in the peanut jar and tossing them in your mouth....and then there's lifting the glass of beer, etc...

[Tony]

Originally Posted by tv_vt

I rode a century Saturday with a Di2-equipped bike. Was riding the next evening with my wife and happened to see her twist her left hand as she shifted into the big ring.

Later I commented that I might get her a Di2 setup and mentioned that I must've saved a ton of calories using Di2 instead of mechanical shifters over the course of the 100 mile ride.
Let's say I shifted 1000 times (10 times per mile - that's possible given how rolling the course was - maybe it was even more, don't know). The simple press of a single finger versus way more force needed for mechanical shifters had me thinking I saved at a minimum a few hundred calories.

But who knows. Any thoughts on this? Any real studies? I know pros choose to use mechanical for courses like P-R, but most often are using electronic shifting. Do they know something we don't?

Shifting a well maintained mechanical takes little effort and quieter than Di2.
If someone has issues with their hands than I can see it making a difference in the amount of effort needed to shift, however that effort is marginal

[berserk87]

Originally Posted by CunegoFan

If you can burn a few hundred calories by moving your fingers then computer games must be the greatest exercise known to man.

Great point. There would be no fat kids anywhere if this were true.

[dgauthier]

I found this article about how many calories it takes to click a mouse (I'm going to hazard a guess that it's about as hard to click a Di2 shifter as it is to click a mouse):

https://mashable.com/2013/03/13/mouse-click-calories

"On average, 16.7 micromoles of ATP (Adenosine triphosphate) are consumed in moving one gram of muscle for one second. So, the total amount of ATP burned to move 11.7 grams of muscle in the index finger is approximately 195 micromoles (11.7g×16.7μ mol/g). There are 7.3 calories in one mole of ATP energy, so the number of calories burned in clicking the mouse equals about 1.42 (7.3/1000) X 195)."

However, it appears they managed to screw up the math. A micromole is *one millionth* of a mole, not one thousandth. So the result is not 7.3 X .195, it's 7.3 * .000195, or .00142 calories. So 1000 presses of Di2 would require about 1.42 calories.

Since it requires moving your entire hand to shift a mechanical shifter, how much energy does it take to move your hand? Well, the human hand weighs about half a kilo. (Don't ask me how I know.) Your hand is about 500/11 or 45 times bigger than your finger, so it would take 45 times more energy to move your hand. So to shift a mechanical shifter 1000 times would take about 45 * 1.42 calories, or 63.9 calories over a century ride. (We burn about 600-800 calories an hour cycling, so that sounds about right.)

That's a little less than one slice of bread. So instead of springing for Di2 for your wife, just give her a slice of bread before the ride, and you'll both be on equal footing!

[R3awak3n]

this is a great excuse to get a electronic group but at the end of the day it is still an excuse to get some sweet gear

[zmalwo]

Di2 would burn more calories in the end because you need to work a few days extra to come up with that money to buy Di2 components. Getting Di2 components for your wife is an excellent idea because women have smaller hands and weaker grip so Di2 will dramatically improve their quality of life same as disc brakes, so was I told.

[dgauthier]

Originally Posted by zmalwo

di2 would burn more calories in the end because you need to work a few days extra to come up with that money to buy di2 components. (...)

lol.

[Bostic]

Every time I have done the Mt. Tam Double Century the next day my left hand is just done from the amount of front derailleur shifts. That particular double more so than the other tough ones require way more chain ring shifts. I'd like to try it with DI2 someday. I'll make sure to eat enough calories at the end of the ride to offset anything saved.

[Mark McM]

Originally Posted by Bostic

Every time I have done the Mt. Tam Double Century the next day my left hand is just done from the amount of front derailleur shifts. That particular double more so than the other tough ones require way more chain ring shifts. I'd like to try it with DI2 someday. I'll make sure to eat enough calories at the end of the ride to offset anything saved.

I've heard it argued that electronic shifting can be beneficial for ultra-marathons, not for energy savings, but because after many, many hours in the saddle, the hands can cramp and shifting can become difficult. Electronic shifting can also be a blessing for those with hand mobility or strength issues. But for your average rider who has normal usage of their hands? I can't see it making any meaningful difference (in terms of energy or fatigue).

[Matthew]

You have way too much time on your hands.

[Elefantino]

This is a total spit-take worthy thread.

[tv_vt]

Glad you're enjoying it. I've found it very entertaining and informative myself.