Kirk and Katie Mauthner, 40 page report

The ability of a belayer to apply enough gripping force to a rope to successfully arrest a falling rescue load is of prime importance when using any belay device that requires a positive gripping response on behalf of the belayer. Belays using figure 8 plates, slot type belay plates, the Münter hitch and others, all require different levels of belayer gripping ability for different levels of impact forces. The minimum levels of gripping abilities exhibited by the population raise serious concerns about the use of any such belay device in rope rescue work. To add to this concern is that the weaker grippers are not readily identifiable by obvious features such as their size. This report is the summary of over 300 tests conducted to assess human gripping ability as it specifically relates to rescue work.