We’re currently in the height of prepping for College Showcases and Combines for high school football athletes looking to build out their recruiting profiles and increase their recruiting stock. As mentioned in our 40yd Dash Race Model Blog , when it comes to tests in American Football, the 40yd Dash is the hallmark!

40yd Dash Race Model Blog

Knowing the importance put on the 40yd Dash, coaches and athletes need to have a knowledge/appreciation for the accuracy for various timing processes. In this article we will highlight the various timing strategies used, their accuracy and what the current gold standard for sprint timing is based on the research.

The Various Sprint Timing Strategies

This day in age there are what feels like hundreds of options to pick from when it comes to sprint timing. Stop watches and hand times, hand-start laser-finish, laser-start laser-finish, GPS units, time-motion analysis, iPhone/Android apps, the list goes on. With that said, before we go into demonstrating the accuracy of each timing strategy, we think it’s valuable to clearly define each one.

Hand Time:

Timing utilizing a hand held stopwatch from start to finish. When using a stopwatch the practitioner administering the test should look to start the watch on the first movement. For most, this is when the back foot moves or the down hand moves.

Hand-Start Laser-Finish:

A laser is defined as an infrared beam photocell that is projected out of one side of the unit and then hits the reflector on the other side that transmits the beam back. One set of timing units are set at the 40yd line to time a laser finish. The start is what defines this specific method of timing by utilizing a hand-held start. The practitioner, much like hand timing, must start the timer on the lasers by pushing a button on a remote based on the first movement. As with hand timing, it’s recommended to go on the first movement of the back foot or down hand.

Laser-Start Laser-Finish:

For this, the finish is the same as before, as a set of lasers are put on the 40yd line to stop the timer the second an athlete breaks the laser between units. The laser start can be administered two ways, with a set of lasers on the 0yd line or by a laser unit on the ground tracking the hand. If you are using a set of units on a tripod, the timer starts as soon as the athlete stands up out of the 3 point stance and trips the laser. This tends to be less accurate compared to a set of ground lasers. With ground lasers, the athlete sets up and breaks the laser with his/her hand in the 3 point starting position, the timer starts the second the athlete moves their hand, reconnecting the laser.

Single vs Double Beam Laser:

There are two types of laser timing systems; single and double beam. A single beam laser has one laser set at a specific height that is broken when any part of the body crosses the beam. A Double beam laser has two separate lasers on the same axis (yard line) and both need to be broken at the same time to provide a true time.

GPS Units:

As of recent years, Global Positioning Systems have begun being used to assess speed. These GPS units are coupled with an accelerometer that is put in a bra-like material in order to accurately hold the unit between an athlete’s scapula. These units have the ability to track running velocity which can be time-stamped utilizing programs built into the GPS systems software to calculate specific times during a run. In general, GPS units are more popular for their ability to calculate MPH in a specific race.

Time-Motion Analysis:

TMA, as the name suggests, is the practice of analyzing the demands of the race and specific time spent in each movement during the race by videotaping with a high-speed camera and then analyzing on motion analysis software. While using the software one can get time-stamps to retroactively determine sprint times.

Accuracy of Your Chosen Timing Strategy

Now that we’ve developed a standardized definition for each of the testing strategies and/or systems, it’s time to look into the accuracy (validity/reliability) of each method.

While hand times have been shown to have no significant difference between practitioners, research has shown that when compared to electronic laser times, a hand time 40yd dash is up to -0.24 seconds faster. This is the widely accepted difference in 40yd dash testing.

As for laser-finish timing, The International Association of Athletics Federations (IAAF) defines a true break in the infrared beam as when the torso breaks the signal. In 60% of cases, single beam lasers show a double tripped time (both the arm/knee and torso breaking the signal) when positioned at chest height or below the thigh. That said, if the lasers are correctly positioned at hip height, only 4% of cases get double tripped, which demonstrates the vital importance of the laser setup by the practitioner. As for Single Beam lasers, they have a standard error measurement of 0.03s.

Dual or Double beamed lasers have shown greater accuracy and should be used when looking to administer accurate and reliable data. This method has a standard error measurement of 0.02s (slightly more accurate than single beam lasers).

If/when using GPS units, a practitioner needs to make sure and understand the standard measurement of error associated with the difference between Hz (Hertz) of each specific unit. Simply put, lower Hz equals a bigger error rate. These methods will soon take over the field, but will have to produce enough valid research on sprint velocity compared to the current typical error rate of 3-15%. Currently, correlations of GPS units to lasers have shown to have a ‘unclear to moderate’ level of accuracy.

Finally, Time-Motion analysis is found to be as accurate as the specific equipment used to capture the race is (laser timing). When compared with lasers, TMA has an r score (correlation) of 0.99, which is practically perfect. This method is very reliable however, it comes with disadvantages due to cost and the time it takes to retroactively report a sprint time. Another disadvantage is that you need a qualified practitioner to analyze the videos accurately to report valid/reliable times.

What Is The Gold Standard?

So what does all this mean? To date, Dual Beam Lasers continue to be what is considered research grade and the gold standard for sprint timing. That being said, with the advancements in technology we believe in the coming years that various other options (like GPS) will be more clearly validated in the research and are quickly becoming the new gold standard.

How We Time At EForce

Our staff has been a part of multiple NFL Pro Days, High School Combines and Sprint Testing for academic research over the last decade. At our EForce Verified Combines we use laser timing systems, while implementing the specific timing process utilized by the Nike Opening and Student Sports sponsored combines events. This ensures that athletes receive the most accurate 40yd Dash times within a standardized testing environment. We also work to keep our event number low to minimize tester-related fatigue and to give athletes maximum attention.

At the end of the day, in most cases, timing is better than not timing... but as coaches we have an ethical responsibility to inform athletes on the error rates associated with your timing strategy.

Erik Jernstrom

Director of Sports Performance @ EForce

https://pubmed.ncbi.nlm.nih.gov/25785707/

https://pubmed.ncbi.nlm.nih.gov/26660758/

https://www.researchgate.net/publication/291495309_Time-Motion_Analysis_Procedure_in_Team_Sports_Example_for_Youth_Basketball
https://pubmed.ncbi.nlm.nih.gov/25254901/