Functional comparison of pronation and supination strengths.

Studies have shown that functional activities involving pronation and supination, such as turning a doorknob or a screwdriver, involve wrist positions of extension and/or ulnar deviation. Previous studies of isometric forearm pronation and supination strength have utilized a neutral wrist position, resulting in a possible underestimation of true functional strength. Twenty healthy subjects between the ages of 24 and 45 years were assessed for isometric pronation and supination strength using cylinder, screwdriver, and doorknob handle adaptations. Maximal strength in both pronation and supination was observed with the use of the doorknob handle. Although pronation strength was exceeded by supination strength within all three handle adaptations, the difference was statistically significant for the screwdriver and doorknob handles. The results suggest that in clinical and research-oriented testing of maximal forearm rotation strength, further consideration must be given to the terminal grip device and positioning of the wrist.