Motor hand strength is a composite measure of 2 tests: grip and pinch strength.

Grip and pinch strength are measured bilaterally using the Jamar hydraulic hand and pinch dynamometers (Lafayette Instruments, Lafayette, Indiana). Participants are asked to perform each test twice with each hand. The average of these 4 trials for each test represent the performance scores for grip and for pinch strength, in pounds of pressure.

The performance scores are then converted to a z-score, using the baseline mean and standard deviation of all study participants, with men and women scaled separately. The z-scores for grip strength and pinch strength are then averaged to yield a composite measure of hand strength.