The reliability of one vs. three grip trials in symptomatic and asymptomatic subjects

Grip strength is used in the assessment of hand and upper limb function. Current recommendations state that taking the mean of three repeated grip trials provides more reliable results than only one trial. A repeated measures, crossover design was used. Sixty-six subjects were recruited (22 asymptomatic subjects, 22 following carpal tunnel decompression, and 22 following flexor tendon repair). Grip strength testing was performed on a Jamar dynamometer using a standardized testing protocol. Pre- and post testing pain levels were recorded using a verbal analogue scale. Each subject's grip strength was tested four times, twice using a single trial protocol and twice using three grip trials in random order. Intraclass correlation coefficients (ICC) (2,1), 95% confidence intervals, and standard error of measurements were calculated. A two-tailed paired samples t-test was used to investigate the difference between the grip strength values obtained and the changes in verbal analogue scale. High levels of test-retest reliability (ICC>or=0.85) were found for the three methods of grip strength testing (one trial, the mean of three trials, and the best of three trials). The mean values of grip strength generated for each method of grip strength testing produced comparable results. A significant difference (p>or=0.0001) was observed in the verbal analogue scale scores following one trial and three in all three sample groups. Clinically acceptable levels of reliability (>or=0.91) were demonstrated by all three methods of grip strength testing other than the mean of three trials for the asymptomatic group. Distribution of the ICC results and the elevated verbal analogue scales associated with three trials suggest that the use of one grip trial may be appropriate. This study suggests that one maximal trial is as reliable as and less painful than either the best of, or, mean of three trials.