Water SKi Binding Release Loads: Test Method and Results

Abstract

The existing technical literature is discussed along with injury data and a method for measuring the loads associated with release from water ski bindings. Numerous case studies of water skiing-related lower extremity injuries have been published. There do not appear to be any statistically valid epidemiological studies or studies of water ski injury risk factors. An analysis of the 1990 water skiing injury data contained in the U.S. Consumer Product Safety Commission's (CPSC) National Electronic Injury Surveillance System (NEISS) is presented. Nationwide estimates of the number of water skiing related injuries associated with various portions of the body are made. An injury mode breakdown for various structures of the lower extremity is presented. The injury incidence rate is approximately 0.203 injuries per 1000 skier days for all injuries, and 0.041 injuries per 1000 skier days for possibly orthopedic injuries of the lower extremity. A method for measuring the release loads of water ski bindings is described. A load cell that measures three orthogonal forces and three orthogonal moments is utilized. Human subjects remove their feet from the bindings in prescribed release modes while data are collected by an automated data acquisition system. Forward bending and torsional release loads were measured for various types of bindings, including no-wrap, low-wrap and high-wrap bindings. As expected, in those situations where an axial force pushes the foot down against the ski, none of the bindings releases the subject's foot under torsional loading. Torsional release torques for the various bindings vary with the amount of heel liftup. The release loads measured are discussed in the context of release requirements for snow ski bindings. In general, the torques required to release from water ski bindings are smaller than the release torques recommended by snow ski binding release standards.