Abstract
This study aimed to analyse the impact of high and low flexibility levels of hamstring
and quadriceps muscles on physical fitness and neuromuscular properties in professional
soccer players. 62 male professional soccer players participated in this study and
performed 2 instrumented flexibility tests (passive straight leg raise [PSLR] and
quadriceps flexibility [QF]). Anaerobic performance was assessed using countermovement
jump (CMJ), Abalakov vertical jump, 20-m sprint, and Balsom agility test. A k-means
cluster analysis was performed to identify a cut-off value of hamstring and quadriceps
flexibility and classify players as high hamstring flexibility (HHF) and low hamstring
flexibility (LHF) or high quadriceps flexibility (HQF) and low quadriceps flexibility
(LQF), respectively, according to the PSLR and QF performances. The LQF players performed
better than HQF on CMJ (p=0.042, ES: 0.64) and Balsom agility test (p=0.029, ES: 0.68).
In addition, LQF showed higher muscular stiffness than HQF players (p=0.002, ES: 0.88).
There were no significant differences between HHF and LHF groups. When pooling the
HQF and LQF players’ data, the Pearson’s correlation showed significant moderate positive
association between muscular stiffness and QF (r=0.516, p<0.001). These results support
the rationale that baseline stiffness is likely to influence athletic performance
rather than flexibility level in soccer players.
Key words
athletic performance - tensiomyography stiffness
