Relationship between Movements of the Foot and Electromyographic Activities of Lower Leg Muscles in Young Women

젊은 여성의 발동작과 몇몇 하퇴근 근전도와의 관계

As the crippled persons work mostly in a sitting position and would be engaged in a foot-pressing job, it is necessary to assess their degree of participation of important muscles in various modes of foot activities. In this regard, it deems to be urgent to establish the reference standards for healthy persons. The present study has been undertaken to determine the degree of participation of the M. tibialis anterior, M. gastrocnemius and M. soleus in heel pressing, foot-flat pressing and forefoot pressing motion under varying forces, and in order to compare the electrical activities of three muscles with each other, and to analyse the time sequence between force and appearance or disappearance of EMG recording. Sixty-three healthy young women ranging from age of 18 to 23 were examined. The results obtained were as follows: 1. Participation of three muscles in foot movement under varying forces: A) Both gastrocnemius muscles or left soleus muscle did not contribute to heel pressing motion. Activity of both tibialis anterior muscles was the greatest among three muscles at heel pressing motion and the degree of their activities was proportional to force. B) Activities of left tibialis anterior muscle and both gastrocnemius muscles were negligible under 3 kg force at foot-flat pressing movement. Left gastrocnemius muscle did not contribute to foot-flat pressing under 6 or 9 kg force. Although activities of both soleus muscles and both tibialis anterior muscles were small, the degree of their activities increased with force at foot-flat pressing movement. C) Activities of both tibialis anterior muscles were negligible under 3 kg force at forefoot pressing motion. Activity of both soleus muscles was the greatest among 3 muscles and the degree of their activities increased with force at forefoot pressing motion. Both tibialis anterior muscles participated in forefoot pressing motion with severe exertion. 2. Electrical activities by foot movement under varying forces : A) Electrical activities were prominent in both tibialis anterior muscles and the level of their activities was linear with force at heel pressing motion. The degree of participation of both soleus muscles was small at heel pressing motion. B) Electrical activity of tibialis anterior muscle was the greatest among 3 muscles at foot-flat pressing movement and was followed by that of soleus muscle. Level of electrical activities increased with force in left soleus muscle and right tibialis anterior muscle at foot-flat pressing movement. C) Electrical activity of both soleua muscles was the greatest among 3 muscles at forefoot pressing movement and that of tibialis anterior muscle was next to soleus muscle. Level of electrical activities was proportional to force in left tibialis anterior muscle, right gastrocnemius muscle and both soleus muscles at forefoot pressing movement. 3. Time between starting signal and initiation of contraction of heel pressing and forefoot pressing motion in 3 muscles was longer than that of foot-flat pressing movement. Time of relaxation in 3 muscles was longer than that of contraction under varying forces. EMG recording appeared before initiation of contraction in both tibialis anterior muscles at heel pressing motion and in both soleus muscles at forefoot pressing movement under varying forces. Time of initiation of contraction was similar in both sides of tibialis anterior muscles under varying forces and time of onset of contraction at foot-flat pressing motion was the shortest. 4. Forefoot pressing movement would be encouraged in paralysis of tibialis anterior muscle, while heel pressing motion would be encouraged in paralysis of triceps surae muscle.