Measuring grip strength in older adults: comparing the grip-ball with the Jamar dynamometer

Decreased grip strength is a predictor of adverse outcomes in older adults. A Grip-ball was developed that can be used for home-based self-monitoring of grip strength to detect decline at an early stage. The purpose of this study was to evaluate the reliability and validity of measurements obtained with the Grip-ball in older adults.

Forty nursing home patients and 59 community-dwelling older adults 60 years or older were invited to participate in this study. Grip strength in both hands was measured 3 consecutive times during a single visit using the Grip-ball and the Jamar dynamometer. Test-retest reliability was described using intraclass correlation coefficients. Concurrent validity was evaluated by calculating Pearson correlations between the mean Grip-ball and Jamar dynamometer measurements and between the highest measurements out of 3 trials. Known-groups validity was studied using t tests.

Eighty eight participants (33 men) with a mean age of 75 (SD = 6.8) years were included. Intraclass correlation coefficients for the Grip-ball were 0.97 and 0.96 for the left and right hands, respectively (P < .001), and those for the Jamar dynamometer were 0.97 and 0.98 for the left and right hands, respectively (P < .001). Pearson correlations between the mean scores of the Grip-ball and the Jamar dynamometer were 0.71 (P < .001) and 0.76 (P < .001) for the left and right hands, respectively. Pearson correlations between the highest scores out of 3 trials were 0.69 (P < .001) and 0.78 (P < .001) for the left and right hands, respectively. The t tests revealed that both the Grip-ball and the Jamar dynamometer detected grip strength differences between men and women but not between nursing home patients and community-dwelling older adults. Grip-ball measurements did not confirm higher grip strength of the dominant hand whereas the Jamar dynamometer did.

The Grip-ball provides reliable grip strength estimates in older adults. Correlations found between the Grip-ball and Jamar dynamometer measurements suggest acceptable concurrent validity. The Grip-ball seems capable of detecting "larger" grip strength differences but might have difficulty detecting "smaller" differences that were detected by the Jamar dynamometer. The Grip-ball could be used in practice to enable home-based self-monitoring of grip strength in older adults. However, for implementation of the Grip-ball as a screening and monitoring device in practice, it is important to gain insight into intersession reliability during home-based use of the Grip-ball and clinical relevance of changes in grip strength.