February 2007 - A study by researchers from the University of California at San Francisco and McMaster University in Ontario
published in Human Factors has measured carpal tunnel pressure to help establish how much the wrist can be flexed safely if nerve damage
associated with carpal tunnel syndrome is to be avoided.
Researchers explain that the wrist is vulnerable in any work involving the hands; repeated bending and flexing can lead to carpal tunnel syndrome. They measured pressure placed on the nerve in the carpal tunnel in various wrist positions in 37 healthy men and women aged between 22 and 50. They found that bent or flexed (non-neutral) positions increased pressure on the nerve and concluded that injury is likely when sustained pressure reaches 30mmHG.
To maintain safer pressure levels, they recommend that postures do not exceed the following: 32.7 degrees for sustained wrist extension (bending the hand back), 48.6 degrees for wrist flexion (bending the wrist toward the palm), 14.5 degrees for ulnar deviation (sideways toward the small finger), and 21.8 degrees for radial deviation (sideways toward the thumb).
Researchers suggest that these findings could form the basis of simple guidelines to improve equipment design, identify high-risk activities and help workers avoid nerve damage.