Valuation of football players level by lower limbs strength using CMJ 2.1

Introduction: The football players (FP) need high level of lower limbs strength during matches such as during headshots (Reilly and Korkusuz, 2008). Testing the vertical jump height is widely used to determine the lower limbs strength. The aim of this study was to determine if the new functional test Countermovement Jump 2.1 (CMJ2.1) (Alberti et al., 2015) was able to characterize the level of athletes. Methods: 49 FP (age: 21.0±7.0 yrs; height: 178.1±6.0 cm; weight: 73.6±5.3 kg) were recruited from local high and low level football teams (HL: n=26 and LL: n=23, respectively). The participants were tested on bipodalic countermovement jump height landing on two legs (CMJbip), landing on right leg (CMJ2.1R) and landing on left one (CMJ2.1L). The FP were also tested on right and left monopodalic countermovement jump height (CMJR and CMJL, respectively). In accordance to Shapiro-Wilks’ normality test, Unpaired t-test or Mann-Whitney U test and Paired t-test or Wilcoxon test were performed using Aabel (versione 3.0.3; Gigawiz Ltd. Co., Tulsa, OK, USA). A p value lower than 0.05 was considered statistically significant. Results: No statistical difference was detected in CMJbip between HL and LL (38.2±5.4cm and 35.9±4.7cm, respectively). However, statistical differences were detected in CMJR (p<0.001) and CMJL (p<0.001) between HL and LL. Furthermore, a statistical difference was found in CMJ2.1R (p<0.05. HL: 33.5±5.5cm; LL: 30.4±4.2cm), but no statistical difference was found in CMJ2.1L (HL: 33.3±4.9cm; LL: 31.1±4.4cm). In both groups, no statistical differences were detected between CMJ2.1R and CMJ2.1L. Grater statistical differences between CMJbip and CMJ2.1 were found in LL (CMJbip vs CMJ2.1R = p<0.001; CMJbip vs CMJ2.1L = p<0.001) than in HL (CMJbip vs CMJ2.1R = p<0.01; CMJbip vs CMJ2.1L = p<0.01). Discussion: No statistical difference found in CMJbip between HL and LL could be explain by lower contribution of coordination skill and unspecific dynamic sport movement during this test as compared to monopodalic CMJ test. Indeed, the HL FP reached higher CMJR and CMJL than LL because of different strength level performed using one leg. Lower values recorded during CMJ2.1 as compared to CMJbip are due to unconsciously neuromuscular mechanism that permit to reduce the impact on the ground after jumps (Withrow et al., 2006). The differences detected in LL between CMJbip and CMJ2.1, in both right and left legs, are higher than HL. The smaller is the difference in vertical jump height between CMJ2.1 and CMJbip, the higher is the FP level. References: Alberti G, Boccolini G, Rossi A (2015). XXIV edition of the International Conference on Sports Rehabilitation and Traumatology. London. Reilly T, Korkusuz F. (2008). New York: Routledge. Withrow TJ, Huston LJ, Wojtys EM, Ashton-Miller JA. (2006). Am J Sports Med.