ELECTROMYOGRAPHIC ACTIVITY IN EXPERT DOWNHILL SKIERS USING FUNCTIONALKNEE BRACES AFTER ANTERIOR CRUCIATE LIGAMENT INJURIES

We studied six expert downhill skiers who had sustained anterior cruci ate ligament injuries and had different degrees of knee instability. T he aim was to measure possible changes in electromyographic activity r ecorded from lower extremity muscles during downhill skiing in a slalo m course without and with a custom-made brace applied to the injured k nee, Surface electrodes were used with an eight-channel telemetric ele ctromyographic system to collect recordings from the vastus medialis, biceps femoris, semimembranosus, semitendinosus, and gastrocnemius med ialis muscles from both legs. Without the brace, the electromyographic activity level of all muscles increased during knee flexion. The bice ps femoris muscle was the most activated and reached 50% to 75% of the maximal peak amplitude. With the brace, the electromyographic activit y increased in midphase during the upward push for the weight transfer and the peak activity occurred closer to knee flexion in midphase. Al so, the uninjured knee was influenced by the brace on the injured leg, a decrease in electromyographic activity was seen in midphase. Spearm an's rank correlation revealed a significant correlation between an in crease in biceps femoris activity of the injured leg and increasing kn ee instability. We suggest that the brace caused an increased afferent input from proprioceptors, resulting in an adaptation of motor contro l patterns secondarily modifying electromyographic activity and timing .