Relationship between key performance indicators and force-velocity profile of elite sprinters and football players

Introduction: This study is based on the research of Brűnn and Švantner (1), who compared key performance indicators (KPI) of an elite sprinter and players of national football teams. Although the sprinter excelled in jumping abilities (SJ, CMJ, BJ, RSI), he did not achieve the highest strength values in any of the selected metrics. Švantner and Brűnn (2) also compared sprint acceleration force-velocity profile of elite sprinters and elite football players, and it was found that while football players showed superior force production and application effectiveness, sprinters maintain high efficiency in force at increased velocities. The aim of this study is to follow up and correlate non-specific KPI and force velocity profile of elite sprinters and football players. Methods: The first part of the research was collecting key performance indicators data of 13 elite level male soccer players and an elite level sprinter, who completed squat jump (SJ), counter-movement jump (CMJ), broad jump (BJ), depth jump (DJ – RSI index) tests, ankle extensors’ force assessment (AEF), isometric 30° knee flexion (ISO30), eccentric nordic hamstring (ENH), isokinetic knee extension (IKQ) and knee flexion (IKH). The second part of the research was to complete a 30m linear sprint, which was assessed by 1080 Sprint device. The research sample consisted of 38 male elite soccer players and 6 elite level sprinters. The testing of football players took place on match day +3 days, with RAMP protocol warm up. Macroscopic F-v profiles were calculated based on running speed, body mass and the basic laws of motion applied to the center of mass. Last phase of the research was to correlate non-specific KPI (SJ, SMJ, BJ, DJ, AEF, ISO30, ENH, IKQ, IKH) and force velocity profile (F0, V0, RFmax %, DRF %) of elite sprinters and football players. The statistical analysis was done in Python program. Results: In our research sample, which consisted of elite football players and sprinters, only one moderate positive correlation (0.63) was found between strength in eccentric nordic hamstring exercise and momentum (kg∗m/s). Weak correlation (0.47) was observed between ankle joint extensors isometric strength and momentum (kg∗m/s), suggesting the importance of adequate strength level of individuals in specific positions. Almost moderate correlation (correlation coefficient: 0.47) between the standing long jump and the value of V0 (m/s) and at the same time no correlation (correlation coefficient: -0.06) between the standing long jump and the value of F0 (N/kg) is a very interesting finding. Given that the standing long jump represents horizontal force production, these findings are rather unforseen. Unexpectedly, only weak relationship was found between RSI and V0 (m/s) (0.41) and no relationship between isometric hamstring strength and F0 and V0 respectively. Conclusions: While the sprinter excelled in jumping abilities (SJ, CMJ, BJ, RSI), he did not achieve the highest levels of strength across any of the selected metrics (1). The second part of this study underscores the fact, that while football players demonstrate greater force production and application effectiveness, sprinters exhibit high efficiency in force at elevated velocities (2). No or weak relationships were found between KPI and the force-velocity profile of the research sample in our correlations. Another finding is the fact that despite the different movement strategies to reach maximal speed between football players and sprinters, these facts did not substantially affect the final results.