The 40-yard dash has long been the standard for evaluating football players' speed. It's believed that 40 yards was chosen as a yardstick because it's the average distance of a punt and times would allow coaches to determine players' ability to sprint from the line of scrimmage to cover punts.

Traditionally, the test was measured by hand, with coaches standing at the finish line with a stopwatch. However, many clinics and combines now use electronic timing as a way to improve the accuracy of their measurements.

Unfortunately, such electronic times are often compared directly with hand times when, in fact, a correction factor should be used when comparing them.

Differences in Electronic Versus Hand Times
Track coaches have long known that hand times produce faster results because human reaction-time results in the watch being started a split-second after movement actually occurs, while electronic systems detect this movement instantaneously, resulting in the clock running for a slightly longer period of time.

Track officials correct for this difference by adding .24 seconds to a hand-timed 100m to convert it to an electronic time.

Should football coaches not also use such a correction factor when comparing hand and electronic times over 40 yards? If so, what is the factor?

The Study - Electronic Versus Hand Times
A study at Truman State University was performed to determine an appropriate conversion factor. Multiple repetitions of 40 yard runs were conducted, with hand and electronic times for the same subjects recorded and compared.

Hand timing is typically initiated upon the first hand movement out of a three-point stance, and ends when the player's torso (shoulders or chest) crosses the finish line.

Electronic timing starts when the player lifts his hand from a sensor pad and ends when he crosses an infrared beam at the finish line. The beam is set at a height of about 4 feet.

Results
The study determined that the difference between hand and electronic times was .12 to .19 seconds, with the hand times being faster. A correction factor of .16 seconds was suggested - this is similar to the widely accepted human reaction time for visual stimulus of .19 seconds.

So, if your player runs a 40-yard dash in a hand-timed 4.40 seconds, his electronic equivalent would be 4.56 seconds.

Human Variation Recommendation
As was identified in this study, there is considerable variation in the skill of the timers themselves. The researchers suggest that any testing situation use the same timer(s) for all tests so the results within that group remain consistent.

Reference: William Brechue, Jerry Mayhew, Fontaine Piper & Jeremy Houser, Comparison Between Hand- And Electronic-Timing Of Sprint Performance In College Football Players, Missouri Journal of Health, Physical Education, Recreation and Dance, 18, 50-58, 2008.

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© 2009, Physical Education Update, www.peUpdate.com

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