Critical Velocity during Intermittent Running with Changes of Direction

Purpose We tested the hypothesis that critical velocity (CV) during intermittent running with changes of direction (Int/CoD) is reliably and accurately identified from a simple shuttle field test. We also tested the hypothesis that CV during Int/CoD running is not equivalent to continuous linear running. Methods Young adults performed a custom shuttle test of intermittent sprint running to reveal critical velocity. Sprints were 18.3 meters per direction, with rest between sprints of 15 seconds for 3 minutes, 10 seconds for 2 minutes and no rest for 2 minutes (7 minutes total). To test reliability, the CV shuttle test (CVST) was performed twice. To test validity, blood lactate was assessed during two separate trials inclusive of 5% above or below CVST end velocity. To explore task specificity, CV during CVST was compared to CV obtained from 3 linear running time trials. Results Total distance and CSVT end test velocity were similar between visits (864 ± 21 m and 3.23 ± 0.13 m/s vs 900 ± 30m and 3.21 ± 0.15 m/s, respectively). At 5% above CVST end velocity, all subjects failed to complete 20 minutes and had unstable blood lactate values. A steady state blood lactate profile was observed during trials 5% below end velocity and all subjects completed the trial. The CV from the CVST was lower than the CV from linear running ([INCREMENT] -17 ± 6 %), highlighting the importance of test specificity for threshold determination. Conclusion The CVST provides a reliable and accurate determination of CV and can be used by coaches, athletes, and trainers to better understand the physiological impact specific to practice or competitions involving intermittent change of direction running. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and the results of the present study do not constitute endorsement by ACSM. Conflicts of Interest and Source of Funding: No conflicts of interest are declared. This project was supported by internal Nike, Inc funding mechanisms. © 2018 American College of Sports Medicine

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