Comparison of Three Timing Systems: Reliability and Best Practice Recommendations in Timing Short-Duration Sprints

Abstract

Bond, CW, Willaert, EM, and Noonan, BC. Comparison of three timing systems: reliability and best practice recommendations in timing short-duration sprints. J Strength Cond Res 31(4): 1062-1071, 2017-With the importance placed on athletic speed, it is important to use a valid and reliable timing system, particularly in sprints of short duration. Unfortunately, many of the commonly used timing systems have not been rigorously evaluated. This study aimed to compare results from a single-beam infrared photocell (PC), single-beam laser with a microprocessor (LA), and a previously validated video camera (VC) sacrum-based timing system; and in doing so, determine these systems' reliabilities, and establish best practices for increasing reliability. It was hypothesized that PC and LA times would be different from VC times and show reduced reliability compared with VC. Fifteen athletes performed 5 repetitions of a 60-foot maximal effort sprint with split times recorded for the first and second half. Photocell and LA full-time and first-half split times were significantly slower than VC (p < 0.001), but almost identical for the second half split (p = 0.08). Repeated sprint analysis showed that VC tended to have smaller SD compared with PC and LA for first-half split (0.05 vs. 0.08 vs. 0.09 seconds, respectively) and total time (0.09 vs. 0.10 vs. 0.11 seconds, respectively). Time differences were more dependent on initial forward lean and varying body segments triggering the beam, than on a systematic instrument error. The increased variability of PC and LA systems dampen the ability to determine whether meaningful change has occurred. The VC system allows for very valid and reliable measurements of an athlete's sprint time, especially in distances <30 feet.