MUSCLE-ACTIVITY PATTERNS OF ELITE DOWNHILL SKI RACERS DURING LANDING

The purpose of this study was to examine motion and muscle activity in downhill skiing in order to estimate muscular involvement during the landing phase and its potential effect on ACL injury. Specially develo ped 8-channel portable electromyography registration was conducted dur ing three jumps on the Russi jump of the 1994 Olympic downhill slope, and six control jumps were carried out in the laboratory. The results reveal that the skier adapts to the expected loading of the knee, poss ibly by using a learned motor control pattern. It is still not clear, however, how important muscular adaptation to expected forces is. The complex functional EMG pattern that skiers use while landing indicates that ACL rupture caused during a backward fall in downhill skiing mig ht be due to a combination of the boot-top-induced anterior shear, the force generated in the ACL by forceful knee hyperflexion supported by the high bending moment generated by a stiff spoiler, and the possibl e absence of a significant protecting hamstrings force during maximum loading.