Indicators in isokinetic fatigability protocol: What to preserve?

Abstract

Isokinetic tests regularly contribute to the assessment of muscle performance. However, to evaluate an athlete who mainly uses the lactic anaerobic metabolism to perform or in specific pathological contexts, fatigue-resistance protocol could be complementary to short maximal strength evaluation. Although the reproducibility of the protocol has been demonstrated by Bosquet et al. [1] (2010), what about the reproductibility of the measured parameters and various “fatigue index” proposed by dynamometers and used in the clinic and in the literature? Seventeen subjects, moderately active, performed 30 reciprocal maximal concentric contractions on three occasions with one 7–10 days recovery between each session. The peak torque (PT) and the maximal work (MW) of each repetition computed and subsequently use to compile eleven measured parameters and build forty-four index. The reproducibility of each parameter and index was evaluated through their ICC (2,1), SEM and respective MD. The ICC values of the measured parameters for the knee extensors are almost always higher than 0.8 while those for flexor range between 0.7 and 0.8. The ICC values for built “fatigue index” are less than 0.7 and 0.5 respectively for the extensors and flexors. No significant difference was observed between the reproducibility of PT and that of MW (whether for the extensors or flexors or for the measured parameters and “fatigue index”). In view of the values obtained in our population, it appears that no “fatigue index”or calculated quotient (quotient of the last x repetitions by the first x or accumulated repetitions by the best…) seems sufficiently reproducible for clinical or scientific use! Only the measured parameters such as the best repetition, total or partial sum have a (very) high or excellent reproducibility and can therefore be used in clinical or research domain.