Grip Force Safety Margin in Rock Climbers

Abstract

When holding an object, grip force (Gf) is larger than the smallest force needed to prevent slipping (Gmin). The unnecessary grip force is termed safety margin (SM = Gf - Gmin). Because some hand injuries in rock climbing are largely encouraged by excessive grip force, safety margin was examined in a set of expert climbers, and compared to a set of non-climbers. Subjects were asked to hold a heavy or a light object during either a short or a long duration. We focused on the relative safety margin (RSM = 100 × SM/Gmin) adopted at the initiation of each trial. With the heavy object, climbers and non-climbers had similar RSMs (155 versus 148 %). With the light object, higher RSMs were reached, albeit smaller in climbers as compared to non-climbers (232 versus 386 %). Surprisingly, all subjects exhibited larger RSMs at the initiation of a long trial (246 versus 215 %). We conclude that expertise in rock climbing is not accompanied by key changes in RSMs that increase the likelihood of hand injuries. On the other hand, the fact that grip force is so crudely optimized at large load, especially when planning to sustain a hold, does promote the risk of hand injury in climbers.

grip force - rock climbing - hand injury - endurance - safety margin

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1 As opposed to endurance studies, in which subjects had to maintain a given level of force [[14], [19]], a crucial difference is that here, the level of grip force was not explicitly imposed; as long as Gf was superior to Gmin, subjects were free to adjust their grip force.