The complex peripheral structures serving speech may be divided into three main functional groups: those of breathing, voice and articulation. It is possible to study the muscular movements within each of these groups and the various possible combinations of movements between them. Normal speech displays exquisite harmony within the separate groups and in their combinations, while certain types of abnormal speech, notably stuttering, show a disharmony in the combination of the three primary groups of muscles and also within each group.
Halle,1 Ten Cate,2 Gutzmann,3 Fletcher4 and others have studied spasms in the breathing musculature of the stutterer, and all agree that tonic and clonic spasms occur in all cases. Halle and Ten Cate were among the earliest investigators in this field, and both recorded various disturbances and abnormalities in breathing. Fletcher made an intensive study of the temporal relationships between thoracic and abdominal breathing. Gutzmann
TRAVIS LE. STUDIES IN STUTTERINGI. DYSINTEGRATION OF THE BREATHING MOVEMENTS DURING STUTTERING. Arch NeurPsych. 1927;18(5):673-690. doi:10.1001/archneurpsyc.1927.02210050005002