Functional Screening Tests: Interrelationships and Ability to Predict Vertical Jump Performance

There are several methods used in sports science to identify asymmetries in athletes, given their purported relevance to injury prevention and performance optimization. We aimed to verify whether asymmetries provided by isokinetic assessments, jump tests, and tensiomyography (TMG) are associated with each other, and whether their respective functional indices are related to jumping ability. TMG parameters, unilateral and bilateral squat-jump (SJ) and countermovement-jump (CMJ) performances, and peak torque in knee-extension and flexion with angular velocities of 60^o/s and 300^o/s for twenty-four soccer players were retained for analyses. Asymmetry was detected by examining the percentage difference between dominant and non-dominant legs. The median-split technique was used to identify the best and worst performers in SJ and CMJ tests. Results revealed that the asymmetries detected in the three different methods were not interrelated. Curiously, better performances in SJ and CMJ tests were associated with higher asymmetry levels. Furthermore, only the knee-extension peak torque at both angular velocities was correlated moderately to largely (r=0.48-0.66) with jump performance. Despite their recognized ability to predict the risk of injury, the absence of interrelationships between TMG, isokinetic tests, and unilateral jumps precludes their single use as a unique functional screening diagnostic. Finally, and very importantly, lower-limb asymmetry is not necessarily related to impaired vertical jump performance in soccer players.