Characteristics of Median Frequency According to the Load During Fatiguing Isometric Exercise

등척성 운동시 운동강도에 따른 중앙주파수의 특성

  • Lee, Su-Young (Dept. of Rehabilitation Therapy, The Graduate School Yonsei University) ;
  • Shin, Hwa-Kyung (Dept. of Rehabilitation Therapy, The Graduate School Yonsei University) ;
  • Cho, Sang-Hyun (Dept. of Physical Therapy, College of Health Science, Yonsei University, Institute of Health Science, Yonsei University)
  • 이수영 (연세대학교 대학원 재활학과) ;
  • 신화경 (연세대학교 대학원 재활학과) ;
  • 조상현 (연세대학교 보건과학대학 물리치료학과 및 보건과학연구소)
  • Published : 2003.09.17


Median frequency can be regarded as a valid indicator of local muscle fatigue. As local muscle fatigue develops, the muscle fiber conduction velocity decreases, the fast twitch fibers are recruited less, and consequently the median frequency shifts toward the lower frequency area. The aim of this study was to test the characteristics of the median frequency according to exercise load (30% and 60% of MVC on the biceps brachii, 40% and 80% of MVC on the vastus lateralis) during the fatiguing isometric exercise. Thirteen healthy male volunteer students of Yonsei University were recruited. After the testing maximal voluntary isometric contraction, three variables (initial median frequency, regression slope, fatigue index) from the regression line of MDF data were measured in each exercise load. The results showed that the regression slope and fatigue index were significantly different for the biceps brachii, but not for the vastus lateralis initial MDF was not significant difference according to the exercise load on both muscles. The regression slope and fatigue index could monitor physiologic muscle change during fatiguing isometric exercise. The results showed that two MDF variables reflect the local muscle fatigue according to the exercise load.