The short-term reliability of grip strength measurement and the effects of posture and grip span.

PURPOSE: Because of the difficulty in verifying the reliability and validity of grip strength there is still no consensus regarding its measurement, particularly short-term reliability. The present study was conducted to investigate the short-term reliability of grip strength measurement and the effects of posture and grip span. METHODS: One hundred healthy subjects (50 men, 50 women; mean age, 38.2 y; range, 22-58 y) were evaluated. Grip strength was measured twice as a single set by using a dynamometer and the mean value for each hand was recorded. First 3 sets of measurements were performed using 2 different approaches: (1) continuous measurement without rest and (2) interval measurement with a 1-minute rest after each set. Next 1 set of measurements was performed with 3 types of grip span: standard grip span (which was measured as one half the distance between the index finger tip and the metacarpophalangeal joint flexion crease at the base of the thumb), +10% of the standard grip span, and -10% of the standard grip span. Finally 1 set of measurements was performed in 3 postures: standing, sitting, and supine. RESULTS: During continuous measurement the grip strength decreased gradually as the number of sets increased. During interval measurement, however, there was no change among sets for both genders and each hand. On the basis of this result subsequent studies were performed using interval measurement. There was no significant difference in maximum grip strength between the standard and +10% of standard grip span measurements; however, the -10% of standard model gave the minimum grip strength in both genders. With regard to posture the minimum grip strength in both genders was obtained when the subject was supine, with no difference between standing and sitting. CONCLUSIONS: Our study showed that interval measurement with a 1-minute rest after each set yielded a constant value; therefore, we advocate this approach for rapid evaluation of grip strength under different conditions. In addition the influence of grip span and posture should be considered to maximize data accuracy.