Comparison between tests of fatigue and force for trunk flexion.

Abstract

A quasi-experimental study was conducted. To compare intraindividual differences between trunk flexion isometric force, fatigue during isometric contraction (isometric fatigue), and fatigue during sit-ups (dynamic fatigue). Trunk flexion force and trunk flexion fatigue commonly are used to assess trunk flexion fitness. The use of one test is appropriate only if the tests are highly correlated. This study measured force and either isometric fatigue (time to task failure, n = 79) or dynamic fatigue (number of sit-ups in 2 minutes, n = 73) in self-selected, healthy secondary school (I-III) subjects. In 15 subjects, both isometric and dynamic fatigue were measured. After control was used for upper body mass, the R2(adj) was 0.34 between isometric force and isometric fatigue, 0.31 between isometric force and dynamic fatigue was, and 0.27 between dynamic fatigue and isometric fatigue. Including gender in the model did not affect the results. The lack of a high correlation between trunk flexion isometric fatigue, dynamic fatigue, and isometric force suggests that health care professionals should be careful to select the test that answers their particular needs or question.