Announcer

Welcome to Brain Stuff from www.HowStuffWorks.com where smart happens.

Marshall

Hi, I’m Marshall Brain with today’s question.

How do I burn calories on a stair machine?

Let’s start with normal stairs, and understand why they burn calories, and then we can look at stair machines as a special case. The How Stuff Works article on How Horsepower Works explains the unit of power known as horsepower. One horsepower is 550 foot-pounds of work per second. If a horse or an engine were to raise a 550-pound load at a rate of one foot per second, it would exerting one horsepower of effort. So let’s imagine that you are standing at the bottom of the Empire State Building in New York, and you start climbing the stairs. Let’s also imagine that you weigh 150 pounds. If each step raises you one foot, and if you walk up the stairs at a rate of one step every second, then you are doing 150 foot-pounds of work every second, or a little more than a quarter of a horsepower. If you were to run up the steps at a rate of four steps every second, you would be doing 600 foot- pounds of work every second, or 1.09 horsepower. One horsepower exerted over an hour is equal to 641 calories. So if you were to run up the stairs at a rate of 550 foot-pounds of work every second for an hour, you would burn off 641 calories.

It is hard for human beings to maintain that level of effort for an entire hour. A normal human might be able to maintain a rate that burns 200 or 300 calories per hour, which is unfair when you consider that you can gain all of that back by eating a single candy bar. On a stair machine it doesn’t appear that you are going anywhere, but really you are. Imagine that you are climbing a long ladder, but the ladder is sinking in the mud as fast as you are climbing it. It you were to stop climbing, you would sink into the mud, too, so you have to keep climbing. It would appear that you are going nowhere, but in fact, you are climbing at the same rate that the ladder is sinking, so you are doing work. The lack of movement is an illusion. A stair machine creates the same kind of illusion, as anyone who has used one can tell you, you are doing work.

Do you have any ideas or suggestions for this podcast? If so, please send me an E-mail at Podcast@HowStuffWorks.com.