Reproducibility of Controlled Force Exertion Measurements Computed by a Quasi-Random Target-Pursuit System

The reproducibility of measurements and measurement error of controlled force exertion was examined based on target-pursuit of quasi-random waveforms. 30 college students were required to match their grip strength to a changing demand value appearing on the display of a personal computer using visual images in the form of four different quasi-random waveforms. The variable was the sum of the differences over time between the demand value and produced grip strength. Intraclass correlation coefficients (ICCs) for measurements one day apart were low or moderate for quasi-random waveform displays, with mean frequencies of 0.01, 0.05, 0.07, and 0.09 Hz (ICCs = .37, .73, .57, and .57, respectively). Measurements at a 1-wk. interval showed statistically significant improvements in performance at all quasi-random waveform frequencies. The total error between test and retest, and the systematic error between tests, remained relatively small as mean frequency increased. Tests that use the quasi-random waveform displays of 0.05 Hz and over can be useful in documenting controlled force exertion.