Grip strength testing reliability.

The purpose of this study was to investigate the test-retest reliability of isometric grip strength testing using the Jamar dynamometer. Thirty-three subjects, 16 men (mean age = 37.4 years) and 17 women (mean age = 35.5 years), were assessed on two separate occasions using four methods to determine grip strength score. The methods used were (1) the score of one trial, (2) the mean score of two trials, (3) the mean score of three trials, and (4) the highest score of three trials. All five handle positions of the Jamar dynamometer were used during testing. Although still within the limits of acceptability, position 1 was significantly less reliable when compared with the other handle positions. Because the four methods of determining grip strength score were not significantly different in reliability, it was not possible to recommend any method as being more accurate. To analyze curve shape further, grip strength curves for the strongest and weakest men and women were compared by transforming points on the curves into percentages of the maximum value. Transformed curves for both strong and weak subjects were almost identical, indicating that, for this sample, "flattening" of the grip strength curves was a function of weak grip. The present data do not support the use of raw score curve shape as an indicator of sincerity of effort during grip strength testing.