Pedometer data
What are they?
A pedometer is a pager-sized device that straps to your waist and counts the number of steps you take.
Are they accurate?
Pedometers detect the vertical movement of your hips as you walk. A pedometer is most accurate, studies show, when a person is walking faster than 3 mph. As speed decreases so does accuracy and this is due to the mechanics of walking at a slower speed. People tend to shuffle or move their feet at slower speeds and this results in less vertical movement of the hips than is needed by the pedometer to count steps. Accuracy at 3 mph or more can exceed 96% and at 2-3 mph it can drop to 74%. Below 2 mph, accuracy can be as low as 60%. Needless to say, a brisk walk is what’s needed here.
How do pedometers work?
There are 2 types of pedometers in terms of internal workings. The first type is a mechanical spring lever that has a horizontal bar suspended by a spring parallel to the ground. When you walk and induce a vertical force or motion on the bar, it moves up to complete an electrical circuit. Each closing and opening of the circuit is counted as one step.
The second type is also a beam but with a weight at the free end. At the other end, the beam is connected to a piezoelectric cell. When vertical motion is applied, a pressure is induced in the cell that produces a voltage that is proportional to the applied force. These voltage swings are used to count your steps.
Which type is better?
Piezoelectric type pedometers are more sensitive at lower speeds and tend to be more accurate below 2 mph. They are also not as sensitive to tipping over from their horizontal position as a spring lever type is. A piezo type pedometer may only see a 10% reduction in accuracy when tilted at speeds below 2mph, while a spring loaded lever may see up to a 60% reduction in accuracy below 2mph. So if you are older or overweight and walk slowly, the piezoelectric design is probably the way to go.
Pedometers must be worn at the waist in line with the leg. If you have trouble sticking to your waist, you can stick to your sock. This should give you the same vertical movement needed.
Test the accuracy of your pedometer
When you get your new pedometer for the first time and want to check its accuracy or want to perform interim checks on one you now own, set the pedometer to zero. Carefully count 100 steps to see what kind of result you get. Remember that you are looking for +/-10% accuracy, which means anything in the range of 90-110 steps. If you don’t get it in this range, try changing the position of your pedometer and walking again and see if that makes a difference. Some people have different walks and it’s just a matter of trial and error to find the best position for you.