The stability of isometric trunk flexion measurements

The purpose of this study was to determine (a) the number of isometric trunk flexions needed to obtain a stable measure of exertion, (b) the least variable parameter to be used to quantify maximum isometric trunk flexion, and (c) the time interval needed to obtain the least variable measure of maximum isometric flexion. Ten adult males served as subjects. Each subject performed five trials of one maximum isometric trunk flexion. Each trial lasted for 5 s. The results showed (a) only one trial is required to obtain a stable measure of the maximum torque generated during isometric flexion, (b) more than one trial is required to obtain a stable measure of the average torques, (c) maximum torques are more stable measures than average torques, (d) the first second of a 5-s exertion does not yield stable measurements, and (e) individuals adopt different exertion strategies during each trial.