Relationship between the angle of the coronoid process of the mandible and the electromyographic activity of the temporal muscle in skeletal Class I and III individuals.

The aim of the present study was to verify the relationship between the angle of the coronoid process of the mandible in the latero-lateral direction and electromyographic activity of the anterior part of the temporal muscle in skeletal Class I and III individuals. Forty-five volunteers were assessed subdivided into two groups, according to angle ANB, in Class I and III. Two radiographic examinations were performed, one lateral cephalogram to measure angle ANB and one frontal cephalogram to measure the angle of the coronoid process. The electromyographic examination of the volunteers' temporal muscles was performed. Statistical analysis of the data showed that the relationship between the angle of the coronoid process and the skeletal class was negative for both classes analysed. The relationship between electromyographic activity of the temporal muscle and angle of the coronoid process was negative for Class I individuals. In the Class III group, smaller angles of the coronoid process were related to higher values of electromyographic activity of the temporal muscle. There was no statistically significant difference between the electromyographic activity of the temporal muscle in skeletal Class I and III individuals. Based on the results obtained, it was concluded that there was no influence of the skeletal classes analysed on the angle of the coronoid; the angle of the coronoid process may be influenced by the electromyographic activity of the temporal muscle in the Class III group; the electromyographic activity of the temporal muscle is not influenced by the skeletal class in Class III individuals.

Electromyographic study of the sternocleidomastoid muscle in head movements.

The function of the sternocleidomastoid muscle in head movements of 30 young individuals (19-28 years old, both sexes) was studied electromyographically using a TECA TE-4 electromyograph and Beckman surface electrodes. Action potentials were found in the following head movements: free heterolateral rotation; free homolateral inclination; free and counter-resistance protraction; free and counter-resistance flexion and free extension. These movements were performed with the subjects seated and in supine position.

Participation of the sternocleidomastoid muscle on deep inspiration in man. An electromyographic study.

The sternocleidomastoid muscle (SCM), which is responsible for the mechanical action in the majority of the head movements, is also considered an accessory muscle for respiration. Its action in the inspiratory movements was studied electromyographically in 30 healthy young adults by considering the types of respiration, the different forms of deep inspiration, the breathing effort and the body position of these subjects. A prominent activity was found in those subjects whose respiration was of the costal type when they breathed rapidly and roughly and during the breathing effort. An outstanding difference of the action potentials of the SCM muscle was not observed during variation of the body positions.