AUTHOR=Ruf Ludwig , Altmann Stefan , Müller Katharina , Rehborn Anja , Schindler Fabian , Woll Alexander , Härtel Sascha 

TITLE=Concurrent validity of countermovement and squat jump height assessed with a contact mat and force platform in professional soccer players

JOURNAL=Frontiers in Sports and Active Living

VOLUME=Volume 6 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2024.1437230

DOI=10.3389/fspor.2024.1437230

ISSN=2624-9367

ABSTRACT=Purpose: The aim of this study was to assess the concurrent validity of a contact mat against force plates to measure jump height in countermovement jump (CMJ) and squat jump (SJ) in professional soccer players. 
Methods: 23 male professional soccer players performed the CMJ and SJ, which were concurrently recorded using a portable contact mat (SmartJump) and a portable dual force plate system (ForceDecks). Equivalence testing between both systems (contact mat vs force plate) and the two methods (impulse-momentum vs flight-time and flight-time vs flight-time) was performed compared to equivalence bounds of ±1.1 cm for the CMJ and ±1.6 cm for the SJ. Additionally, 95% Limits of Agreement and intraclass correlation coefficients (ICC) were computed. 
Results: Mean differences for the impulse-momentum vs flight-time comparison for CMJ (3.2 cm, 95% CI (2.3–4.1)) and SJ (2.7 cm, (1.8–3.6)) were non-equivalent between both systems. Limits of Agreement were larger than the equivalence bunds for CMJ and SJ, while ICCs were good (CMJ, 0.89, (0.76–0.95)) and excellent (SJ, 0.91, (0.79–0.96)). As for the flight-time vs flight-time comparison, mean differences were non-equivalent for the CMJ (1.0 cm (0.8 to 1.2 cm)) and equivalent for the SJ (0.9 cm (0.7–1.1 cm)). Limits of Agreement were narrower than the equivalence bounds for CMJ and SJ, while ICCs were excellent (CMJ, 0.995, 95% CI (0.989–0.998); SJ, 0.997, 95% CI (0.993–0.997)).
Conclusion: Our findings indicate that the SmartJump contact mat cannot be used interchangeably with the ForceDecks force platform to measure jump height for the CMJ and SJ.