Reliability assesment of the tests for maximal isometric muscle force and rate of force development of m. quadriceps femoris in opened and closed kinetic chain depending on knee angles

Abstract

The purpose of this study was to assess the reliability of tests for the assessment of maximal isometric muscle force (F(max)) and the explosive force (viewed through the rate of force development - RFD(max)). Tests were carried out for muscle m. quadriceps femoris, in the open (OKL) and closed (CKC) kinetic chain under 6 different angles in the knee joint, ranging from 80˚-130˚ (with changes of at 10˚, 180˚ represents the fully extended leg). The study tested 'intra-assay'(between 3 attempts within a testing session)' and inter-test' (test-retest) reliability presented through ICC coefficients. In addition, differences between the results achieved in different angles for the same test, for Fmax and RFDmax were examined by ANOVA with repeated measures. Nine students of FSPE (23.5±1:38 years) performed each three isometric contractions, by taking tasks of: seated leg extension (OKC) and seated leg press (CKC). Tests were carried out in chronological order: OKC1-OKC2, CKC1-CKC2 (Firstly the OKC test, two times in a span of 72 hours, and then the CKC on the same principle). The results suggest that the CKC is generally more reliable test, but that the reliability of maximal isometric and explosive force varies depending on the selection of the task / test, articulated joint angle and selecting variables for monitoring ('inter' vs 'intra' and 'avg' vs 'max'). The differences in the results of monitored variables among the articular angles indicate that in the OKC m. quadriceps femoris behaves in accordance with F-L (force-length) relation, while the mechanical conditions of the bone-joint levers in the CKC are crucial for the expression of muscle force.