Biomechanics of ice tool swinging movement. Section 3 : Biomechanics, Chapter 10 In: The Science of Climbing and Mountaineering
Résumé
Ice climbing is a recent competitive practice involving quadruped locomotion with ice tools in each hand and crampons on each foot. The progression resulted in contradictory actions: the climber has to determine the best target following by a swinging motion to anchor the axe combining accuracy and strength, so that the climber can pull on the axe to climb up the cliff. Finally, the axe is unanchored by the climber. These successive actions are numerously repeated during the progression conducting to fatigue conditions. Analyses of competitions indicated that performance is related to shorter times either for anchor or swing. The low expertise climbers spent more time in static conditions to find the target, using symmetric location of four supports conducting to greater fatigue. The biomechanical data suggested that experts adjust their movement to the kind of ice axe. They were characterised by high controlled coordination of the upper limb joints. The cocking phase appeared with a proximo - distal coordination associated to lower muscular co - activations. The strike phase is characterised by high joint moments with peak co - activations just before the impact stiffing the upper limb to transmit maximal force and velocity to the pick. The distal wrist joint controls the accuracy of the impact. The high co - activations of the digitorum muscles conditioned the strength of the hanging that appeared very important for transmission of force - velocity - accuracy actions from the upper limb joints to the axis. Fatigue affected more the grasping muscles then the muscles involved in the ballistic movement