Most treadmills have digital readouts that tell you how far you've traveled as well as your current pace. However, the factory settings for these readouts aren't always accurate --- you may be running even faster than you think you are. Testing a treadmill allows you to gauge the accuracy of your readouts for more complete workout information.
Treadmill Accuracy
In "Freshman Running: A Guide for Beginning Runners," Rick Morris notes that many treadmill manufacturers believe customers won't notice if one or more of the calculators are incorrect. Factory settings are often off by as much as 10 percent, he writes. This makes a big difference in training times. Morris notes that a difference of 10 percent can change a 7:00 mile into a 7:40 mile.
Treadmill Belt Measurement
To test your treadmill's readouts, you need to measure the belt. Authors Edward Howley and B. Don Franks explain how to do this in "Fitness Professional's Handbook." You can do it with a meterstick and chalk. First, mark the treadmill belt with a piece of chalk --- this is your starting point. As you advance the treadmill belt manually, mark each successive meter with a chalk number. When you reach your starting mark, count up the number of meters you marked. This is the belt's length in meters.
Measuring Revolutions
Once you know your belt length, you can test the accuracy of the speedometer. Howley and Franks suggest you set the treadmill to a particular speed in miles per hour and use a stopwatch to find out how long it takes the belt to complete 20 revolutions. When you have the result, measured in seconds, divide it by 60 to find out how many revolutions per minute your treadmill makes. Multiply this result by your belt length in meters to get your belt's rotating speed in meters per minute. To convert this result into miles per hour, simply divide by 26.8. Your result should match the speed at which you set your treadmill to time the 20 full revolutions.
Treadmill Settings
Most treadmills allow you to adjust your digital readouts. You will need to consult your owner's manual to find out how to do this for your particular model. If your owner's manual doesn't tell you how to do this, you may need to call the treadmill's manufacturer and ask for instructions. You may also be able to ask a fitness professional at your local gym or contact a nearby fitness equipment retailer; if they sell the same model, they may be able to advise you.
Benefits
Using a properly calibrated treadmill allows you to obtain a more accurate measurement of your fitness level. If you're planning on training for a 5K or 10K, for example, it's important to know your exact speed and time --- you may be placed in a particular starting group based on this time. Having an accurate assessment of your ability will help you plan a training course and set achievable goals.
