Characteristics of EMG Median Frequency and Torque in Relation to Low Back Angle During Isometric Back Extension Exercise

등척성 운동 시 요추의 각도에 따른 중앙주파수와 토크의 특성

  • Park, Kyoung-Hee (Dept. of Rehabilitation Therapy, College of Health Science, Yonsei University) ;
  • Kwon, Oh-Yun (Dept. of Rehabilitation Therapy, College of Health Science, Yonsei University) ;
  • Jang, Kuen (Dept. of Biomedical Engineering, College of Health Science, Yonsei University Institute of Biomedical Engineering, Yonsei University) ;
  • Kang, Sung-Jae (Dept. of Biomedical Engineering, College of Health Science, Yonsei University Institute of Biomedical Engineering, Yonsei University) ;
  • Kim, Young-Ho (Dept. of Biomedical Engineering, College of Health Science, Yonsei University Institute of Biomedical Engineering, Yonsei University)
  • 박경희 (연세대학교 보건과학대학 재활학과) ;
  • 권오윤 (연세대학교 보건과학대학 재활학과) ;
  • 장근 (연세대학교 보건과학대학 의공학과 및 의공학 연구소) ;
  • 강성재 (연세대학교 보건과학대학 의공학과 및 의공학 연구소) ;
  • 김영호 (연세대학교 보건과학대학 의공학과 및 의공학 연구소)
  • Published : 2001.05.21

Abstract

Fatigue is the decline in force produced as a result of prolonged muscle activity. Localized muscle fatigue can be identified by a shift toward low in the frequency components of the EMG signal, typically represented by a fall in the median frequency. Previous studies show that a shortened muscle develops a higher fatigue than elongated muscles. The purpose of this study was to investigate the time-related change of median frequency and torque during maximal isometric back extension exercises at different exercise angles ($0^{\circ}$, $12^{\circ}$, $36^{\circ}$, $72^{\circ}$). Twenty healthy subjects (mean age = $24.35{\pm}2.70$) were evaluated in this study. Median frequency was extracted from the EMG signals by fast Fourier transform (FFT). Initial median frequency and the slope of median frequency change over time were computed from linear regression analysis. Pearson's product moment correlation was used to quantify the relationship between slope of median frequency and torque. The results were as follows: 1) Significant differences in y-intercepts of torque regression equation with respect to exercise angle were shown. However, there were no differences in the slopes of the median frequency and torque, and y intercept of the median frequency among exercise angles. 2) There was no significant correlation between slope of median frequency and torque. 3) But there was moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slope of median frequency and torque. But results showed that median frequency and torque shift were highly correlated in all subjects.

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