How far do you walk in a typical day? You might be surprised at the mileage you clock up pottering round the house, nipping out to the shops, and strolling to work or school. Walking a little bit more is a great way to improve your health and fitness; for some people, this kind of exercise is prescribed as a method of losing weight or getting well again after an operation. How can you keep track of your walking without measuring from a map? Simple! Just wear a handy little gadget called a pedometer that counts each step you make. Ever wondered how they work? Let’s take a closer look!
A step in the right direction? Wearing a simple pedometer can encourage you to take more exercise. According to the sports experts’ research, 5400 to 7900 steps a day is a good target to aim for, though some sources suggest a higher target of 10,000 steps a day.
How does a pedometer work?
Suppose I give you the job of building a little gadget that will measure how far you walk in a day. Sounds like a tricky task to me. You could use something like a click wheel (a large wheel you roll over the ground that clicks each time it turns one complete circuit), but rough or muddy ground is going to cause problems and it’s going to have a job measuring stairs.
Okay, so let’s redefine the problem by considering what walking involves. Every time you walk, your body tilts to one side and you swing a leg forward. Then your body tilts the other way and you swing the other leg forward too. Each tile of the hips and shift of the legs is a step. Assuming each step is pretty much the same length, all we need to do is count the number of steps we make in a day, by counting the number of times our body tilts from side to side. We can then multiply the number of steps by the length of each one to figure out the overall distance walked. This is pretty much how a pedometer works.
Pedometers can measure your steps because your body swings from side to side as you walk. Each swing counts as one step. Multiplying the number of “swings” by the average length of your steps tells you how far you’ve gone.
Early pedometers were entirely mechanical and they worked a bit like pendulum clocks (the ones with a swinging bar powered by a slowly falling weight). The original pedometers used a swinging pendulum to count steps and displayed the count with a pointer moving around a dial (a bit like an analog watch). You fixed them on your waist and, every time you took a step, the pendulum swung to one side then back again, causing the gear to advance one position and moving the hand around the dial.
In this common design of pedometer, there’s an electric circuit inside (red path) that is alternately broken and completed as you make steps. When the pedometer tilts to the left, a step is counted by an electronic circuit (top left). When it tilts the other way, the circuit is broken and reset ready to count the next step. Note how the hammer becomes part of the circuit: it has an electrical contact at one end wired to the circuit by a light metal spring. Other pedometers work in different ways, but most of the cheaper ones use a moving hammer and interruptible circuit in broadly the same way.
Modern pedometers work in a very similar way but are partly electronic. Open one up and you’ll find a metal pendulum (a hammer with a weight on one end) wired into an electronic counting circuit by a thin spring. Normally the circuit is open and no electric current flows through it. As you take a step, the hammer swings across and touches a metal contact in the center, completing the circuit and allowing current to flow. The flow of current energizes the circuit and adds one to your step count. As you complete the step, the hammer swings back again and the circuit is broken, effectively resetting the pedometer ready for the next step. The pedometer shows a count of your steps on an LCD display; most will convert the step count to an approximate distance in miles or kilometers (or the number of calories you’ve burned off) at the push of a button. Note that in some pedometers, the hammer-pendulum circuit works the opposite way: it’s normally closed and each step makes it open temporarily.
How accurate is a pedometer?
Counting steps with a pedometer sound super-scientific, but you need to remember that it’s only an approximate measurement. Not all your steps will be correctly counted and some false movements (jolts in the road as you ride in a car, for example) might be counted as steps too. Don’t take the count too seriously; assume that it’s in error by least 10 percent (the best electronic pedometers claim 5 percent accuracy).