Research article

Effects of hand position on maximum grip strength and discomfort

Kong Y. Song Y. Jung M. Lee I.
Ergonomics Australia – HFESA 2011 Conference Edition, 2011 11:44.

Abstract

Background: Maximum grip strength can be used in designing work methods or workstations ergonomically. Though there is a standard protocol for measuring maximum grip strength, workers usually assume different upper-limb postures from the standard posture. It is known that grip strength can be affected by different postures. In many work conditions, the hand position can be determined as the ratio of the full reach distance of the worker. The grip strength data at various hand positions could be used practically in designing work methods or workstations. Aims: The objective of this study was to measure grip strength and perceived discomfort at different hand positions and to investigate the effects of shoulder angle and reach distance on grip strength. Method: Maximum grip strength and discomfort were measured in 58 male volunteers at 15 different hand positions in standing posture. The hand position was defined by five hand directions (i.e. 0°, 45°, 90°, 130°, and 180°) of the shoulder flexion angle, and three hand-shoulder distances (i.e. 100%, 75%, and 50%) of arm reach. After gripping maximum strength, the subjects rated their perceived discomfort using a visual analog scale (VAS). Results: Analysis of variance on grip strength and discomfort rating showed significant effects of hand-shoulder distance, hand direction and their interaction (p<0.05). No significant interaction effect of grip strength between hand-shoulder distance and hand direction was shown (p>0.05), while there was a significant interaction effect of discomfort and hand direction and hand-shoulder distance (p<0.05). Conclusions: This study showed different effects on grip strength when individuals use different hand positions in order to grip. It is recommended that hand position should be over 75% of arm reach and in the reach direction of between 45° and 135° of the shoulder angle for optimum grip strength and comfort.

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