Pedometers

Feb 01, 2004

How Do They Work?

Pedometers are motion sensors that measure steps. Usually a lever arm suspended from a spring moves up and down with the motion of walking or running. The arm works like a pendulum. An electric circuit closes after each movement and records the step on a digital readout. Most electronic pedometers ask you to input an average step length to aid accuracy.

More complex accelerometers, which can be attached to the shoe or the waist, detect movement in one or more planes and record distortions in the vertical plane. Results are sent to a display or downloaded to a computer.

Walking speedometers/odometers track speed and distance using Global Positioning System (GPS) technology or accelerometers.

Beyond the Basics

  • distance (mileage)

  • caloric expenditure

  • speed

  • clock

  • stopwatch

  • pulse reader

  • music

  • countdown timer

  • memory chips to store data

  • integration with heart rate monitors or watches

  • and probably more!

How Well Pedometers Work

  • Electronic pedometers are more accurate than older analog models.

  • Many pedometers appear to be most accurate at 80 meters per minute or about 3 miles per hour (mph) (actually, 2.98 mph).

  • Normal walking speed for most people is between 2 mph and 4.5 mph.

  • Whether a pedometer is worn on the left or right side does not appear to affect accuracy.

  • Excess fat at the waist may create inaccuracy.

  • The slower the walking speed, the more inaccurate the step count. This may be because the vertical accelerations of the waist (the pendulum movements) are less pronounced at slower speeds. Also, stride length may be shorter than what is programmed into the pedometer.

  • For frail or shuffling walkers, pedometers are probably ineffective for measuring steps.

  • Distance and caloric expenditure are estimated from the step data, using manufacturers’ proprietary formulas. Some pedometers are more accurate than others.

  • Generally, distance is less accurate than step count.

  • Caloric expenditure is the least accurate measurement.

Critical Element #1: Where You Put It

  • The device has to sit on the waistband or belt so it is horizontal and straight. If the pedometer tilts, it becomes inaccurate.

  • It should sit at the midline of the thigh, or about 4 to 5 inches away from the belly button (depending on body type).

  • A pedometer won’t work in a pocket because the device can’t stay vertical. However, one manufacturer says that hanging it from a lanyard will work.

Critical Element #2: Stride Length Input

  • Walk with a normal gait when measuring your step length.

  • Note that step length decreases when you walk uphill and increases when you walk downhill. For accuracy, you will need to adjust the stride length programmed into the pedometer.

  • Try using water to measure your footprints. Outside on concrete, pour water into a puddle and splash around to get the bottoms of your shoes wet. Then measure your wet footprints from left heel strike to right heel strike. If you measure in inches, divide by 12 to get the number of feet.

  • Walk a measured track where you know the distance, and count your steps. Then divide the distance by the number of steps to get your stride length.

  • Measure a 10- or 20-foot distance and walk it several times, counting steps, to get the average number of steps for the distance. Divide distance by steps to calculate stride length.

Inspire the World to Fitness Ideas

  • Why not offer to help your participants program their pedometers? Sometimes the print is small on the instructions and the terms may be unfamiliar.

  • Could you make measuring stride length a fun activity for the warm-up or cool-down in your class? How about active rest during a personal training session?

Sources

Digi-Walker Pedometer Web site, www.store.yahoo

.com/n-e-wlifestyles; accessed November 2003.

Pedometer Walking, Robert Sweetgall, Creative Walking Inc., 2001.

“Taking Steps Toward Increased Physical Activity: Using Pedometers to Measure and Motivate,” Research Digest, President’s Council on Physical Fitness and Sports, June 2002.

“Validity of 10 Electronic Pedometers for Measuring Steps, Distance and Energy Cost,” Medicine & Science in Sports & Exercise, August 2003.

IDEA Health Fitness Source, Volume 2005, Issue 2

© 2004 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.