Assessment of the reproducibility of strength and endurance handgrip parameters using a digital analyser

A group of 40 healthy individuals (27 women and 13 men) participated in a handgrip test and were retested 1-2 months later. A strain-gauge sensor with a digitised signal and computerized printout was used. A 5-s maximal squeeze test was first made three times, followed by one endurance test with 45%-55% power of the maximal value. The best maximal value was most often (42%) achieved in the third (initial test) or second (retest) attempt. The reproducibility of maximal value was very good; the Pearson correlation coefficient between initial test and retest (r = 0.98) was even slightly higher than in studies with older analogue instruments. The difference of maximal values [361 (SD 109) N, initial test and 368 (SD 110) N, retest] was insignificant. A moderate 12% long-term change in maximal value was statistically significant. Reproducibility of the power factor (integrated area of power with time) was also very good in this short test, correlating closely (r = 0.98-0.99) with the maximal value. Other indexes (grip rate, fatigue percentage and relaxation rate) were not stable enough to be practical. Endurance results were somewhat variable (r = 0.73), which implied in the main variable motivation. Only marked changes of over 50% in endurance were statistically significant. Endurance power increased significantly in the retest, which, in spite of an r-value of 0.82, would make its use in a follow-up study difficult. We found the computer-based handgrip test both precise and practical in assessing maximal voluntary strength; endurance was more difficult to reproduce.