Ask Jack

Jack,
My new bicycle computer displays a calorie count when I ride. How accurate is it?
Ms. Pattie Fattire

Pattie,
Not very. Calories, a measure of heat, are used to measure energy in food and the energy, from food, we burn to power exercise. Calories in a food are measured in a lab. A food is incinerated in a calorimeter and the heat given given off is measured and converted in to calories.
Getting caloric expenditure in humans is not that easy. Calories supply their energy to humans on a cellular level--not an easy place to stick a meter. However, accurate calorie counts can be made indirectly--by measuring the amount of oxygen the body uses to process the calories used to power exercise.
'Calories used' charts for hundreds of activities from typing with an electric typewriter to long distance running come from thousands of measurements of people doing those things while hooked up to an apparatus that measures, minute by minute, their oxygen consumption. The technology to do this and to do it accurately has been in laboratories for over 100 years.
Also, in a laboratory, variables which greatly tax the exercise effort such as headwinds and hills are eliminated.
In fact, calorie counters in treadmills can be quite accurate if variables that effect caloric expenditure, such as the weight of the exerciser and the degree of incline can be programmed in to the machine.
A one-ounce bicycle computer the size and thickness of two Wheat Thins strapped to the handlebars is not that sophisticated. The directions for my Cat Eye VELO8 state clearly how the calories are measured; "The calorie consumption data is only the accumulated value that is calculated from the speed data of every second. It differs from the actual consumed calorie."
What that means is that the computer does not know if your 14 miles per hour is coming from coasting (very little calorie burn) or from standing on the pedals breathlessly cranking up a steep hill (a serious caloric expenditure.) It only knows 14 miles per hour and that is what the count displayed on the screen is based on.
(Remember that even using exercise machines that can account for variables uch as weight and give fairly accurate calorie counts, the result includes calories you would have used if you had been sedentary during that time. Just because you are sitting still does not mean you are not burning calories. To get the contribution the exercise made to your daily caloric expenditure, you would have to subtract the calories you would have burned if you had spent the time not exercising but reading, watching TV or sleeping, from the total.)
I hope this helps you out. Keep up the good work.
Jack
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Bicycle Love: It's Complicated

I love my bicycle. But, like most intense love affairs, its complicated.
My Trek touring bike, a 1985 620 frame with a mishmash of components is easy to love for many reasons. The soft ride that 46 inch wheelbase, axle to axle gives me, the beautiful and shiny and new cobalt repaint job and the touring handlebars that make it comfortable to ride on the drops most of the time, satisfies any bike lust I might have.
But even well oiled and adjusted, the friction shifting 18-speed has its moments. Like the times when wiggling that barcon will just not bring it into gear I am reminded it is not an easy ride to love. And those old style cantilever brakes may me long for the dependable stopping power of V-brakes on a mountain bike.
But brifters (levers that combine braking and shifting) are just not me. I have friction shifted thousands of miles. I like the feel of it when it works which is most of the time. And I rarely ride in a pack so I don't need the precision brifters give. And I like something I can work on in the field. Who has overhauled an STI lever at a park picnic table after a 60-mile ride?
Like I said. Love is complicated. Even when its with a bicycle.
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"Urban Bikers' Tricks & Tips" A brief book review

If your only bicycling trips are a long rides in the country with light traffic that loves you, the book "Urban Biker's Tricks & Tips" will be like a visit to a dangerous land where the most important thing to pack is a bad attitude.
Snarky advice such as, "A car's windshield is most vulnerable at a spot half way down and a quarter of the way across. Caution If you accidentially hit one of those spots with a U lock or the heal of your gloved hand, you might crack the windshield," captures the book's tone.
Yet Dave Glowacz's book has lots of good advice too that all cyclists can use. There are 24 pages on how to buy a lock, where to park, how to secure it and tips on how to recover it if it is stolen. Lots and lots of advice on how to ride in city traffic and lots and lots of pictures to go with the advice.
Never the naif, Glowacz gives advice on when to ride stairs, "When someone's chasing you, especially from a car, stairways can make for a good escape," and"before you run red lights, make sure your bike's in good shape. When you run lights you often must move or stop suddenly. A bike with bad brakes or bad drive train will choke."
There are descriptions on exactly what to do in event of an accidend and how to treat the wounds. Going intermodal is detailed with pages on how to get a bike on a subway, train or airplane and how to pack a bike in a box.
The book is published by Wordspace Press (www.wordspacepress.com) and is $14.95, but I borrowed by copy from the New Orleans Public Library. Its the kind of book you might want to wear your helmet while reading.
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