The Effects of Foot Position on Electromyographic Activity of Knee Extensors in Standing

기립자세에서 발위치가 무릎 폄근의 등척성수축 근전도 활성도에 미치는 영향

  • Kim, Seng-Jung (Dept. of Physical Medicine & Rehabilitation, Samsung Medical Center) ;
  • Kwon, Oh-Yun (Dept. of Rehabilitation Therapy, College of Health Science, Yonsei University Institute of Health Science, Yonsei University) ;
  • Cho, Sang-Hyun (Dept. of Rehabilitation Therapy, College of Health Science, Yonsei University Institute of Health Science, Yonsei University) ;
  • Hwang, Ji-Hye (Dept. of Physical Medicine & Rehabilitation, Samsung Medical Center Sung Kyun Kwan University, College of Medicine)
  • 김성중 (삼성서울병원 물리치료실) ;
  • 권오윤 (연세대학교 보건과학대학 재활학과 및 보건과학연구소) ;
  • 조상현 (연세대학교 보건과학대학 재활학과 및 보건과학연구소) ;
  • 황지혜 (성균관대학교 삼성서울병원 재활의학교실)
  • Published : 2001.05.21

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-angles were within a normal range. They were asked to stand in five different foot positions ($40^{\circ}$ externally rotated, $30^{\circ}$ internally rotated, neutral, $20^{\circ}$ plantarflexed, and $10^{\circ}$ dorsiflexed foot position). The EMG activities of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis oblique (VMO) were recorded in standing by surface electrodes and normalized by 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 EMG activity 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 show significant differences in each foot position (p> .05). The results suggest that the quadriceps femoris may be effectively activated by performing MVC at an externally rotated foot position. Therefore, the externally rotated foot position can 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 foot position on muscle strength after MVC exercise of quadriceps femoris in standing.

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