Laboratory and Field Testing of Alpine and Alpine Touring Ski Equipment Retention and Release Characteristics

Thesis (Ph.D.)--University of Washington, 2016-12Releasable alpine ski bindings were developed and standardized in the 1970s to mitigate the risk of twisting and binding fractures of the tibia-fibula, but they have not been effective at mitigating knee injuries. They have two primary functions: 1) Retention – keep the ski attached to the skiers boot if the loads on the tibia are not dangerous and 2) Release – release the ski from the skiers boot before the loads on the tibia become injurious. Alpine touring is a subset of alpine skiing in which skiers use specialized alpine touring (AT) bindings to ascend non-maintained trails and ski down them. The proliferation of AT bindings has exploded in the last 10 years and the changes and innovations to this sector of the binding market have far outpaced the international standards organization ability to define standardized boot-binding interface geometry or AT boot-binding performance. The relative risk of injury when using AT equipment has not been explored. To address these issues, the objective of this research is quantify the performance of alpine and AT boot-binding systems using standardized laboratory test methods and field measurements to evaluate the risk skiers of lower leg and ACL injuries. Laboratory measurements were performed to compare the retention and release characteristics of alpine boot-binding systems to AT boot-binding systems. When AT boots were mixed with alpine bindings, the release characteristics were altered to the degree that using such a combination would increase the risk of a lower leg injury to skiers. When testing AT bindings with AT boots from different ski boot manufacturers, significant variation in the release characteristics was measured. Anecdotally, many skiers dis-trust the retention function of AT bindings because of this variability in performance, and some manually lock out the release mechanism of the binding, exposing themselves to a high risk of a lower leg injury. In order to improve the performance of AT boot-binding systems, it is necessary to quantify the performance requirements of these systems, defined as the loads they must transmit from the ski to the skier. To this end, field measurements of the loads transmitted through the binding to the skier were performed. The loads at the boot-top and the knee were estimated for male and female skiers using alpine and AT bindings. As a whole, AT and Alpine bindings transfer the same net loads to skiers. However, The toe piece of AT bindings transfers most of the load to the skiers but has a very limited ability to absorb energy, exposing a potential weakness for retention performance. Male and female skiers generate loads that reach the release envelope of the binding. However, females generate significantly greater adduction loads at the knee, a known risk factor for ACL injuries. The lateral force at the binding toe piece was well correlated with knee loads in females but not males, indicating that a binding design could incorporate more sophisticated mechanisms at the toe to reduce peak knee loads in females. Interventions designed for female skiers may not prove beneficial for male skiers