Downloaded from http://journals.lww.com/nsca-jscr by BhDMf5ePHKbH4TTImqenVIiuKVF7qTxsQ5g5E2EGgFTU1Fehj7lZ73nqm3pbkAxDdNJJyOqCKg4= on 02/29/2020 Original Research Seasonal Changes in the Sprint Acceleration Force- Velocity Profile of Elite Male Soccer Players Pedro Jim ´ enez-Reyes, 1 Amador Garcia-Ramos, 2,3 Juan A. P ´ arraga-Montilla, 4 Jos ´ e A. Morcillo-Losa, 4 V´ ıctor Cuadrado-Pen ˜ afiel, 5 Adri ´ an Castan ˜ o-Zambudio, 1 Pierre Samozino, 6 and Jean-Benoˆ ıt Morin 7,8 1 Center for Sport Studies, Rey Juan Carlos University, Madrid, Spain; 2 Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, Granada, Spain; 3 Department of Sports Sciences and Physical Conditioning, Faculty of Education, Catholic University of the Holy Concepci ´ on, Concepci ´ on, Chile; 4 Department of Corporal Expression, University of Jae ́ n, Jae ́ n, Spain; 5 Autonomous University of Madrid, Madrid, Spain; 6 Savoie Mont Blanc University, Interuniversity Laboratory of Motor Biology, Chamb ´ ery, France; 7 Cost of Azur University, LAMHESS, Nice, France; and 8 SPRINZ, Auckland University of Technology, Auckland, New Zealand Abstract Jim ´ enez-Reyes, P, Garcia-Ramos, A, P ´ arraga-Montilla, JA, Morcillo-Losa, JA, Cuadrado-Pen ˜ afiel, V, Castan ˜ o-Zambudio, A, Samozino, P, and Morin, J-B. Seasonal changes in the sprint acceleration force-velocity profile of elite male soccer players. J Strength Cond Res XX(X): 000–000, 2020—This study aimed to describe the seasonal changes in the sprint force-velocity (Fv) profile of professional soccer players. The sprint Fv profile of 21 male soccer players competing in the first division of the Spanish soccer league was evaluated 6 times: preseason 1 (September 2015), in-season 1 (November 2015), in-season 2 (January 2016), in-season 3 (March 2016), in-season 4 (May 2016), and preseason 2 (August 2016). No specific sprint capabilities stimuli other than those induced by soccer training were applied. The following variables were calculated from the velocity-time data recorded with a radar device during an unloaded sprint: maximal force (F 0 ), maximal velocity (v 0 ), Fv slope, maximal power (P max ), decrease in the ratio of horizontal-to-resultant force (D RF ), and maximal ratio of horizontal-to-resultant force (RF peak ). F 0 (effect size [ES] range 5 0.83–0.93), P max (ES range 5 0.97–1.05), and RF peak (ES range 5 0.56–1.13) were higher at the in-seasons 2 and 3 compared with both preseasons (p # 0.006). No significant differences were observed for v 0 , Fv slope, and D RF (p $ 0.287). These results suggest that relevant Fv profile variables may be compromised (F 0 more compromised than v 0 ) toward the end of the competitive season when specific sprint stimuli are not systematically applied. Key Words: linear sprint, maximal force, maximal velocity, maximal power Introduction The ability to perform soccer-specific actions at high speed is one of the main characteristics of high-level soccer players (31). Short accelerations and linear sprints are 2 of the most important actions in soccer because they frequently precede goals and other decisive actions (9,13). The importance of linear sprints is further reinforced by the large number of studies that have been con- ducted to identify effective conditioning programs to improve linear sprint performance in soccer players (3,6,7,26,27). A recent meta-analysis has highlighted that the addition of either resistance training, plyometric training, or sprint training to regular soccer training is effective at enhancing linear sprint performance com- pared with performing only soccer training (combined effect size 5 0.79) (14). However, some practitioners still prescribe specific physical training to improve explosive performance only during the preseason, expecting that soccer training and competitive matches will provide enough stimuli for maintaining the perfor- mance of explosive actions throughout the competitive season. Linear sprint performance of soccer players has been tradi- tionally assessed by the time needed to run a given distance (e.g., time to 20 m) (3,7,26,27). More recently, Morin and Samozino (23) have recommended the assessment of the entire force- velocity (Fv) spectrum during sprint acceleration (i.e., horizontal Fv profile) to obtain more comprehensive and meaningful in- formation about the determinants of linear sprint performance. Owing to the consistent and clear linearity of the sprint Fv re- lationship, the maximal capacities of the muscles to produce force (F 0 ), velocity (v 0 ), and power (P max ) can be determined through the application of a linear regression model (17,30). Other vari- ables that are also known to influence linear sprint performance can also be determined using this novel testing procedure: Fv slope (i.e., the ratio between F 0 and v 0 ), decrease in the ratio of horizontal-to-resultant force (D RF ), and maximal ratio of horizontal-to-resultant force (RF peak ) (23,30). All the variables of the sprint Fv profile (i.e., F 0 , v 0 , Fv slope, P max ,D RF , and RF peak ) can now be simply but accurately determined during an unloaded maximal sprint in which the athlete reaches top speed (30 m is needed in soccer players) through the recording of either the displacement- or velocity-time data (16,29,30). Several studies have already reported the sprint Fv profile of soccer players (4,6,15,17,19–21,24). Baumgart et al. (2) and Jim´ enez-Reyes et al. (17) provided reference values of the sprint Fv profile of soccer players according to age, sex, and level of practice. Mendiguchia et al. (20,21) suggested that the regular monitoring of the sprint Fv profile in soccer players may provide useful information both from a performance and injury pre- vention perspective. Nagahara et al. (24) showed that the sprint Fv profile is sensitive to detect the fatigue induced by an actual Address correspondence to Dr. Pedro Jim ´ enez-Reyes, pedro.jimenezr@urjc.es. Journal of Strength and Conditioning Research 00(00)/1–5 ª 2020 National Strength and Conditioning Association 1 Copyright © 2020 National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.