Reproducibility of maximum isokinetic trunk strength testing in healthy adolescent athletes

BackgroundIn adolescents athletes isokinetic testing is applied to describe population specific characteristics in trunk strength. However, reproducibility of trunk tests used remains unclear. Aim of the study was to evaluate reproducibility of isokinetic trunk strength testing in adolescent athletes.MethodsTrunk strength was assessed twice in healthy adolescents (N=13; 15.9±1.7yrs; 1.73±0.10m; 69.0±17.0kg). Isometric, concentric and eccentric maximum strength measurements in rotation and flexion/extension were performed. Outcome measures were peak torque (PT; [Nm]), normalized peak torque (PT_norm; [Nm/kgBW]) and ratios of right/left rotation and flexion/extension. Intra class correlation coefficient (ICC), standard error of measurement (SEM), smallest real difference (SRD), Bland and Altman analysis (bias; 95%-limits of agreement (LoA)) and Test-Retest-Variability (TRV) were calculated.ResultsICC ranged between 0.65-0.90 in rotation and 0.69-0.94 in flexion/extension. Systematic error varied between -0.15 to 12.3% (rotation) and -7.0 to 8.8% (flexion and extension). TRV in rotation ranged between 14.6-21.3%. TRV in flexion/extension, except isometric extension, was below 15%. SEM/SRD ranged between 12.6/35.0% and 24.0/66.5% in rotation and 7.2/20.0% and 17.8/49.5% in flexion/extension.ConclusionsResults indicate acceptable reproducibility of isokinetic trunk strength measurements for adolescents in the planes tested. This pilot study indicates that maximum isokinetic trunk strength testing seems to be applicable in this special population, but needs further validation.Level of EvidenceLevel IV.