Reliability of a computerized target-pursuit system for measuring coordinated exertion of force.

The purpose was to examine trial-to-trial and day-to-day reliability and sensitivity for measurements of the ability to coordinate exertion of force based on target-pursuit. 30 college students were required to match their grip strength to a changing demand value appearing on the display of a personal computer, using two visual images in the form of a bar chart and waveform. The variable was the sum of the differences between demanded and produced grip strength over time. Analysis indicated high intraclass correlation coefficients (ICC) for bar chart and waveform displays (ICC = .87, ICC = .95, respectively). The limits of agreement, designating the interval comprising 95% of the differences between three measurements in a stable individual, were -14.8 to 99.3% for the bar chart and -3.5 to 113.6% for the waveform displays. One-tailed, paired t tests of the day-to-day measurements showed significant (p < .05) improvement in both the bar chart and waveform displays. ICCs for day-to-day measurements were low-to-moderate for bar chart and waveform displays (ICC = .33 to .71, ICC = .48 to .76, respectively). The limits of agreement between measurements of two trials for day-to-day measurements were -112.2 to 218.6% for the bar chart and -139.2 to 352.8% for the waveform displays. The repeatability coefficients of trial-to-trial and day-to-day measurements for bar chart and waveform displays were 141 and 173%, and 152 and 176%, respectively. The limits of agreement between each test were relatively wide. We believe that these tests, on which the force response is visually guided, can be useful in objectively documenting the ability to coordinate exertion of force.