Search

Purpose: The purpose of this study was to assess the interchangeability of position tracking metrics obtained using global positioning systems (GPS) versus those obtained by a semi-automatic high definition (HD) optical camera system. Methods: Data was collected from a cohort of 29 elite football players (age: 23.1 ± 5.1 years, height: 180.4 ± 5.8 cm, mass: 74.6 ± 6.7 kg) in four matches played in four different stadiums. In two matches 10 Hz GPS (GPS-1, StatSports, Belfast, UK) were used, while in the other two matches augmented 10 Hz GPS (GPS-2, StatSports, Belfast, UK) were used. All four matches were analysed concomitantly using six semi-automated HD motion cameras sampling at 25 Hz (TRACAB, Chyronhego, New York, USA). Results: Mean bias was between 6% and 10% for GPS-1 and 1–4% for GPS-2, respectively. No proportional bias was found (p > 0.184). The SEE within calibration functions (expressed in % to mean) was between 5% and 22% for GPS-1 and 4–14% for GPS-2. While some significant differences existed between GPS-1 and TRACAB (total distance and high-speed), positional tracking variables were highly correlated between GPS-1, GPS-2 and TRACAB (r2> 0.92) with GPS-2 displaying stronger correlations (> r2 = 0.96). Conclusion: In the present study augmented GPS technology (GPS-2) and the TRACAB camera system provided interchangeable measures of positional tracking metrics to allow concurrent assessment and monitoring of training and competition in football players. However, we recommend practitioners evaluate their own systems to identify where errors exist, calculate and apply the regression equations to confidently interchange data. [ABSTRACT FROM AUTHOR]

We analysed the time course of recovery of creatine kinase (CK) and countermovement jump (CMJ) parameters after a football match, and correlations between changes in these variables and match time–motion parameters (GPS-accelerometry) in 15 U-19 elite male players. Plasma CK and CMJ height (CMJH), average concentric force (CMJCON) and average eccentric force (CMJECC) were assessed 2 h before and 30 min, 24 h and 48 h post-match. There were substantially higher CK levels 30 min, 24 h and 48 h (ES: 0.43, 0.62, 0.40, respectively), post-match. CMJECC(ES: −0.38), CMJH(ES: −0.35) decreased 30 min post, CMJCON(ES: −0.35), CMJECC(ES: −0.35) and CMJH(ES: −1.35) decreased 24 h post, and CMJCON(ES: −0.41) and CMJH(ES: −0.53) decreased 48 h post. We found correlations between distance covered at velocities ≤21 km · h−1and changes in CK at 24 h (r = 0.56) and at 48 h (r = 0.54) and correlations between CK and distance covered >14 km · h−1(r = 0.50), accelerations (r = 0.48), and decelerations (r = 0.58) at 48 h. Changes in CMJCON30 min and 24 h post (bothr = −0.68) correlated with impacts >7.1·G. Decelerations >2 m · s−2correlated with changes CMJCON(r = −0.49) at 48 h and CMJECC(r = −0.47) at 30 min. Our results suggest that match GPS-accelerometry parameters may predict muscle damage and changes in components of neuromuscular performance immediately and 24–48 h post-match. [ABSTRACT FROM PUBLISHER]