The Analysis of the Reliability and Factorial Validity in the Basic Characteristics of Isometric F-t curve of the Leg Extensors in Well Trained Serbian Males and Females

The aim of this research was to establish the reliability and factorial validity of different isometric basic characteristics of F-t curve related to leg extensors in well trained and healthy Serbian males and females. Sample consisted of 159 examinees. In order to assess characteristics of the F-t isometric leg extensor force, tensiometric probe and standardized "seating leg extension" test were used. The measurement range was defined by 4 variables regarding the contractile characteristics of the leg extensor isometric muscle force - 1) the level of the achieved maximal force - F_maxLegExtISO, 2) the indicator of basic (general) level of rate of force development - RFD_{BASICLegExtISO}, 3) the time necessary to reach maximal force - tF_maxLegExtISO, 4) basic synergy index. The results showed a high statistical significance of p<0.001 in representability, generalizability and reliability for all the characteristics observed in both genders (Spearman-Brown r - 0.715 to 0.967 for males and 0.713 to 0.941 for females). As for the methodology aspect of testing, the factor analysis demonstrated the necessity of conducting at least three trials, choosing the best result from the two last trials.