기립자세에서 발위치가 무릎 폄근의 등척성수축 근전도 활성도에 미치는 영향

Abstract

This study was designed to identify the effects of foot position on electromyographic (EMG)activity of the quadriceps femoris during maximum voluntary contraction (MVC) in standing. Twenty young adults who had not experienced any knee injuries were recruited. Their Q-angleswere within a normal range. They were asked to stand in five different foot positions (40°externally rotated, 30°internally rotated, neutral, 20°plantarflexed, and 10°dorsiflexedfoot position). The EMG activities of the vastus lateralis (VL), rectus femoris (RF), andvastus medialis oblique (VMO) were recorded in standing by surface electrodes and normalizedby MVC EMG values derived from manual muscle test. The normalized EMG activity levels (%MVC EMG)of muscles in the five foot positions were compared using repeated measures ANOVA. The EMGactivity levels of the VL, RF, and VMO were the highest when foot was externally rotated. The EMG activity levels of the VL and RF were significantly different among the foot positions(p<.05). However, EMG activity levels of the VL, RF, VMO, and VMO/VL ratio did not showsignificant differences in each foot position (p> .05). The results suggest that the quadriceps femoris may be effectively activated by performingMVC at an externally rotated foot position. Therefore, the externally rotated foot positioncan be considered as an effective foot position for quadriceps femoris strengthening exercise. Further studies are needed to identify whether there are differences in the effects of footposition on muscle strength after MVC exercise of quadriceps femoris in standing.