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What burns more energy? Hills vs flats

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What burns more energy? Hills vs flats

Old 06-23-16, 06:50 PM
  #26  
79pmooney
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A couple more thoughts: Elevation gain always costs energy. Lifting 175 pounds of bike + rider 1000' is the same energy burned for the newcomer who spends 8 hours at it and the Tour de France winner who does it 15 minutes. (The fast guy is also encountering wind resistance, though not a lot if the road is steep.) The racer puts out vastly more power, but not energy. Energy is power X time.

The flats are very different. Doing 100 miles in 10 hours of rolling time (10 mph) takes little energy. Doing it in 4 hours takes a lot. The different wind resistances at those different speeds is huge. The fast guy burns 6X the energy of the slow guy (and has to generate 16X the power).

How hard the flats are is almost competely dependent on the speed. Hilly rides are much better defined.

And the wisecrack - want to make downhills count? Ride fix gears.

Ben
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Old 06-24-16, 08:40 PM
  #27  
Corbah
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A kilojoule in the hills is the same as a kilojoule in the flats.


However, there may be more "overhead" to spinning fast. I have a theory that doing 200watts while spinning 100 cadance takes more energy than doing 200watts while spinning 90 cadence.
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Old 06-24-16, 08:59 PM
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Originally Posted by mnsam View Post
Even with an equal amount of up vs down you will spend more time on the uphill portion since you're speed is slower going up so energy consumed will be much greater riding hills. It may take 5 mins to ride up a hill that you can ride down in 1 minute.
Bingo. There is a lot of discussion on this thread about perception of effort but the physics are irrefutable - for a fixed amount of time to complete, a hilly route takes more actual effort (e.g., watts) to complete than a flat route. It's exactly the same math as why airplanes take longer to do a RT when there is a wind blowing, why a RT crossing of a body of water takes longer when there is a current, or why speed decreases even if a crosswind is at 90-deg to the course. For equal time to complete, any undulation increases the actual energy required.

- Mark

Last edited by markjenn; 06-24-16 at 09:03 PM.
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