How many calories?

Joined: November 28th, 2010, 3:09 pm

May 14th, 2018, 3:08 am #1

I don’t count them or anything - I tell people that hiking more often just allows me to eat whatever I want. I hiked up Baldy today (TR tomorrow I hope) and the AllTrails app said that I burned around 4700 calories on this jaunt. I’ve always used a rough number of 150 calories per mile, maybe a few more if going uphill. Anyway, my hike was less than the 23+ miles that would require...
Does anyone here monitor this kind of stuff?




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Sean
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Joined: July 27th, 2011, 6:32 pm

May 14th, 2018, 6:58 pm #2

The nerds at Harvard made a list. Cross-country hiking is one of the mid-range calorie-burning activities. They claim that a 185-pound person burns 266 calories per 30 minutes of XC hiking.  I don't think they factored in altitude, though. Not sure how much that matters.

So: 9x266=2394. Plus another 100 calories for an hour of sitting. That only gets you to 2500 calories burned. It would be hard to justify the 4700 number. According to Harvard, that's like firefighting levels of activity for 4.5 straight hours.
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HikeUp
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Joined: September 28th, 2007, 3:21 am

May 14th, 2018, 8:44 pm #3

How much energy does it take to raise 185#'s about 3900'? Work is the amount of energy that is expended to move a body through some distance against a force that resists that movement, such as, for example, the force of gravity.

Energy expended = Force x Distance = 185 lbs  x 3900 ft = 721,500 ft-lbs = 233 dietary calories (which are actually kilocalories).

So add at least 233 calories to your 2500 to account for change in altitude.

lol

 
Last edited by HikeUp on May 15th, 2018, 3:52 pm, edited 1 time in total.
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Uncle Rico
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May 15th, 2018, 2:08 pm #4



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Joined: November 28th, 2010, 3:09 pm

May 16th, 2018, 4:06 am #5

Thanks for the scientific stuff. I’m part of a JMT group on Yahoo and the general opinion there is about 3500 calories per day are needed for men hikers. I’m pretty sure I didn’t burn that much on my excursion.
For the record, seeing that number allowed me to justify having a giant bacon cheeseburger from Farmer Boys. Totally worth the hike.


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Joined: December 30th, 2012, 5:51 pm

July 18th, 2018, 10:08 pm #6

JeffH wrote:

>I hiked up Baldy today (TR tomorrow I hope) and the AllTrails app said that I burned around 4700 calories on this jaunt.

AllTrails's estimate sounds wildly wrong to me. It depends on what route you took, of course. I've spent some time researching this and writing open-source software that tries to calculate your energy expenditure when running or hiking: http://www.lightandmatter.com/kcals/ . My interest was mainly because I wanted to figure out how hard one run was compared to another, or how a time on one trail run compared to another. The software can make estimates for either hiking or running. This is all based on published data from elite trail runners who ran and walked on an inclined treadmill in the lab.

For testing my software, my standard input happens to be a loop from Manker, up the road to the ski resort, Devil's Backbone, and coming back down the Ski Hut trail. I picked that loop because lots and lots of people seem to do it, so I was able to find lots of GPS tracks online for testing. For that particular loop, hiking (without a pack), my software estimates that a person with a body weight of 66 kg (145 lb) burns about 1000 to 1100 calories. The route is about 9.7 miles, so this is about 108 calories per mile.

> I’ve always used a rough number of 150 calories per mile, maybe a few more if going uphill. Anyway, my hike was less than the 23+ miles that would require...

So your estimates sound roughly right to me, compared to AllTrails's, which seem silly. I assume their software isn't open source and there's no documentation for how it works? I imagine that the average person is probably less mechanically efficient than the trail-running monsters they used for the lab tests, and it's also going to depend on pack weight and body weight.

HikeUp wrote:

> How much energy does it take to raise 185#'s about 3900'?

Elevation gain makes surprisingly little difference if your hike is a loop. The downhills basically tend to cancel out the uphills, unless the grades are *really* steep.

I'm trying to popularize a statistic I call the "climb factor," CF, which is the added percentage of energy required to do a hike or run compared to a flat run. The CF tends to be really small for a loop, which I think tells the truth -- the standard way of stating it in terms of elevation gain is misleading. The CF for the Baldy loop is about 43%, because it's quite steep. But most people don't do much hiking or running that's that steep. For example, the Boston Marathon has about 1100 feet of gain, but its CF rounds off to close to zero (less than 1 %).

> I’m part of a JMT group on Yahoo and the general opinion there is about 3500 calories per day are needed for men hikers. I’m pretty sure I didn’t burn that much on my excursion.

Seems roughly right, if you take a standard 2000 cal/day diet plus another 1500 cal/day expended if you hike 10-20 miles. Almost everyone takes much more food backpacking than they really need.
Ben
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