The Association Between Isokinetic Strength and Strength Asymmetry and Jump Performance in Female Volleyball Players

PurposeSince the use of normalized isokinetic strength was recently proposed to analyze sportive performance, it was aimed to examine relative isokinetic muscle strength as well as absolute strength in jump performance. Secondly, the investigation of the relationship between extremity-based and inter-extremity strength asymmetry and selected jump tasks was aimed.MethodsThirty female professional volleyball players (23.70 +/- 5.27 years) who has at least four training sessions per week participated to study during the pre-season period Peak torque (PT) of knee flexors and extensors at the speed of 60o/s and 180o/s were evaluated using isokinetic dynamometer. Jump height (cm) and relative power (W/kg) of vertical countermovement jump (CMJ) and squat jump (SJ) were tested by optojump photoelectric system.ResultsA positive moderate correlation between PT and relative PT(rPT) at both speeds with jump height was detected (r = 0.365-0.594). It was found that jump power had a positive moderate to good correlation with PT(r = 0.557-0.731) and low to moderate correlation with rPT (r = 0.314-0.601). No significant correlation was found between hamstring/quadriceps ratio and bilateral muscle asymmetry with jump parameters (p > 0.05).ConclusionsDue to the relatively low level of relationship between normalized strength and performance, we suggest carrying out further studies examining the effects of normalized parameters on performance. Considering the findings based on strength asymmetry, the coordinated action of the relevant muscles may come to the forefront during the performance, rather than muscle strength.