Mechanics
Pedometers are designed to count and record the number of steps taken. They are generally worn at the waist or hip so exercisers can track their efforts to reach the daily recommendation of 10,000 steps. Pedometers sense the vibrations or impact that are made when the feet hit the ground while walking. The most common type of system is a pendulum or swing-arm, which makes contact with a post to count each step. Any noise the pedometer makes is because of the pendulum or swing-arm mechanism in action. Basic models will erroneously track any nonstep movement that causes the mechanism to be disturbed, and wearing the device incorrectly can also cause inaccuracies in total steps counted. If stride length is able to be entered, total distance covered can be displayed as well.
Accuracy
No pedometer is 100 percent accurate all of the time. The majority of accuracy depends on correct placement and use of the device. The pedometer must be placed in a vertical position where it can register movement in the hip joint, which signifies a step. If the model measures distance, stride length should be measured using a natural walking gait and entered. Most models will not work if carried in a pocket, purse or backpack. Electronic filters are advantageous for users who want to wear the device all day; it eliminates false steps that are counted when the device is disturbed. According to MedicineNet.com, accuracy increases to 96 percent or more as speeds reach 3 mph or greater. Speeds between 2-3 mph produce accuracy ranges from 74 percent to 91 percent, and that value drops to 60 percent to 71 percent at speeds 2 mph or slower. Walkers tend to not produce distinct vertical displacement required to count accurate steps when moving at slow speeds.
Types/Features
Basic pedometers count steps only, but other features are available. Total distance be can displayed based on a calculation of stride length and steps taken. Entering body weight and possibly other parameters produces a gross caloric expenditure on some models, but this is only an estimate. A timer or "lap" feature allows the user to exercise for a specific time or set time goals for workouts. More sophisticated models eliminate false steps, do not have to be placed exactly vertically or can be carried in the pocket and produce accurate values. Other features include a back-lit display, heart-rate readings, talking devices, alarms, radio stations, or the ability to hook up to an MP3 player, cell phone or computer.
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