Consumer Electronics & Calorie counters

[jimboalee]

I went for a short tootle yesterday. A moderate 25km ( 17 miles eventually ) into Birmingham and back chasing the bus.
I logged the trip with my Garmin 605. 1hr 14 mins at 14.0 mph average for the trip.

After uploading to a MS spreadsheet, calculating speed from distance and time; and knocking out all the datapoints less than 5 mph, my 'rolling' average was 15.75 mph.

I entered all the meteorological stuff in my MS workbook and it told me I should have completed the trip in 1hr 15 mins, at an average of 13.95 mph !!

It was 7 Celcius. I was wearing shorts; and a thermal vest under my long-sleeve, so it told me the total calorific expenditure was 668 kCals, but I should only replace 215.
Garmin had my 'Calories' at 1068. What? A full chicken Dhansak and naan for 75 minutes ride?? Bollocks.

One toasted teacake and a coffee, more like.

 

[Auntie Helen]

There seems to be such a variation in calories. I track my food on a website and it also gives me calories burned for exercise, including cycling at different speeds. It's obviously rather a blunt instrument (cycling calories go in groups of avg speed, i.e. 12-13.9mpg avg one chunk of calories, 14-15.9mph etc).

Anyway, to give you an idea of what this website suggests, Thursday's ride of 3 hours at 12-13.9mph was 2190 calories, yesterday's 54 mins at 14-15.9mph was 845 and today's 40 mins at 12-13.9mph was 487.

I don't know how accurate this is, but I've been keeping to the required net calorie intake (using these figures as to how much extra I can eat) and have been losing 1lb per week over 5 months so I'm doing something right!

I think the chicken dhansak & naan might be more than 1068 calories though!

 

[Dave5N]

There seems to be such a variation in calories. I track my food on a website and it also gives me calories burned for exercise, including cycling at different speeds. It's obviously rather a blunt instrument (cycling calories go in groups of avg speed, i.e. 12-13.9mpg avg one chunk of calories, 14-15.9mph etc).

Anyway, to give you an idea of what this website suggests, Thursday's ride of 3 hours at 12-13.9mph was 2190 calories, yesterday's 54 mins at 14-15.9mph was 845 and today's 40 mins at 12-13.9mph was 487.

I don't know how accurate this is, but I've been keeping to the required net calorie intake (using these figures as to how much extra I can eat) and have been losing 1lb per week over 5 months so I'm doing something right!

I think the chicken dhansak & naan might be more than 1068 calories though!

How do you do that then? (please no unfunny quips about cyber-hunter-gathering)

 

[Auntie Helen]

It's a website called www.myfooddiary.com, although there are UK based sites. I have to pay for it - $9 per month which used to be £4.50 but is now £6.20. It's a good site although I have to enter the nutritional information for most foods that I eat because the standard Yank ones are in weird volume measurements like "half a cup" rather than "150 grams mushrooms".

There's a free UK equivalent www.foodfocus.co.uk but this seemed to think I could eat an extra 900 calories per day over what myfooddiary suggests for me and I can't see how that would work!

 

[jimboalee]

Does the website ask you the weather condition through the ride?
Does it ask you what clothing you were wearing?
Would it know the thermal-conductivity of damp cotton Tee shirts, underneath an Acrylic road jersey when the temperature is 6 Deg C and the Relative humidity is 60% ?

What if you were to put on a race cape half way through the ride? How many calories a preserved by the extra layer of fabric?

What if the sun shines through the clouds? Does it know about Solar-Gain and radiant uptake? AND what if you were wearing black clothes instead of white clothes, how many calories are preserved by this change in condition?


You will find that EVERY calorie counter out there 'Overcooks' the numbers.
To these ends, I don't take any notice of them, except to see how inacurate they are.

 

[Auntie Helen]

Well I know it's a very rough-and-ready tool, but all I can do is go by its numbers as I'm following the food recommendations, using its calorie estimations and losing the amount of weight it says I will.

Just came back from a VERY windy ride today and clearly worked harder than on a windless day, but I suppose it all averages out over time.

 

[jimboalee]

Not neccessarily.
Your forward coefficient of drag will be different from your reverse direction coefficient of drag.
The forward Cd being the greater.

The higher the windspeed, the greater the energy requirement on a circular route.

PS, reverse direction Cd is only possible to measure in a wind tunnel . No-one has been brave enough to ride a bike backwards at a sufficient speed to calc the Cd.

 

[jimboalee]

I've been commuting to and fro to work this last two weeks. Through the cold weather et al.

My Garmin Edge 605 has been telling me how many calories I'm burning.

I've been comparing the Garmin estimate with my own calcs.
IMO, Garmin assumes I am riding in 'Fair' conditions wearing lycra shorts and a road jersey. ie, it has no idea of the weather conditions.

In the sub zero temperatures I experienced each morning, I was wrapped up in three layers top and bottom with wooly hat under my helmet and wooly thinsulate gloves.
Include in the thick socks, my windchill losses were cut to almost zero, reducing my calorific expenditure to near 'motion alone' numbers.


I can adjust the spreadsheet to a level of attire and weather conditions to acheive the Garmin estimate. Garmin will be close to correct when it is 16 Deg C and I wearing shorts and one road jersey; which is of course, "laboratory conditions".

Getting it right, Garmin would need to spend a fortune on software development, so they give a 'cook book' figure.
My question to Garmin - "Why bother if the kCal figure is not representative for 8 months of the year?"
Winter too cold and summer too hot.


FYI, Today, Garmin said 730 kCals. My calcs said 500 kCals - because I was dressed for the weather. Nearly 50% error.

 

[dodgy]

You've hinted at it, but I can't see where you've actually stated it, so here's the question. Are you saying you burn more/less calories in cold weather?
Not a trick question, I'm not one of the smart asses that patrol this forum looking for an argument.

Dave.

 

[jay clock]

My Garmin also talks bollox. I used this site http://www.bikejournal.com/calories_calc.asp to work out that I do 32cal per km. Sure, I use less or more on certain days or rides, but I think it is about right

 

[Fiona N]

Does the website ask you the weather condition through the ride?
Does it ask you what clothing you were wearing?
Would it know the thermal-conductivity of damp cotton Tee shirts, underneath an Acrylic road jersey when the temperature is 6 Deg C and the Relative humidity is 60% ?

What if you were to put on a race cape half way through the ride? How many calories a preserved by the extra layer of fabric?

What if the sun shines through the clouds? Does it know about Solar-Gain and radiant uptake? AND what if you were wearing black clothes instead of white clothes, how many calories are preserved by this change in condition?

Jeez - oh
I would have thought a far more pertinent question would be 'how much climbing did the ride involve?'
Yesterday I did just over 100km in just under 5 hours (riding time). If you just looked up 20kmph you'd have a pretty ordinary cals per hour, maybe 400, say. But then add in 2000m of ascent and it's a completely different story. Add in that it was on a mtb and partly off-road....
The error on these uncertainties must be orders of magnitude greater than whether the sun's shining or not

 

[Bodhbh]

Hrmmm, I've been making the crude assumption of 1000kcal per 20miles for my general riding and it seems to work *about right*. I'm about 80kg and on a MTB with slicks, but tend to carry a fair amout of junk even on short rides (5-10kg).

This is from some online calc(s), but evidence for that is I I'm loosing weight about the rate I expect based on the above, with cycling far and away been my main exercise. Also, learning the hard way, if I'm doing long rides and start bonking, throwing down ~1000kcal in a cafe seems to get me about another 20-30miles till the bonking starts again unless it's really very hilly. Not sure if this is good evidence!

What I do wonder sometimes is that calories burned is often overestimated, but so is calories absorbed. Digestion is not a 100% efficient and varies I assume between foods depending how refined they are. Food kcals are measured afaik by drying it, grinding it down to powder, and blowing it up in pure oxygen to measure the energy output in a bomb calorimeter. You're stomach does not perform like a bomb calorimeter (!!) so maybe there's some compensation.

 

[jimboalee]

Windchill is very complex. It is effected mainly by the boundary layer of water or moisture on the skin.
Some clothing fabrics are efficient in wicking the moisture away, so much so that recently I had ice forming on my sleeves.

For weight loss via burning fat, swimming in the winter sea in just your speedo cossie is fantastic. The disruption to the boundary layer of water next to the skin is allowing cold water to replace heated water, so the body's mechanism struggles to create the boundary layer.

The same principle applies to a cyclist riding through cold air. It is quantified in kJ / m2 . second.