Progressive Muscular Relaxation
Jacobson’s research enabled him to describe several mechanisms that associate muscular tension and anxiety. Above all, he uses the contrast between mobilization and reflux7 to allow an individual to refine his awareness of what is happening in yoga poses a relaxation session. Jacobson’s mobilizations are organized mostly around the flexion and extension of the muscles, with attention on the way a gesture coordinates with respiration. I bend the arm, feeling what is happening in yoga poses the mobilized muscles; then I extend the arm, feeling what is happening gradually as the arms extends further and then relaxes. I can also feel what the movements evoke in yoga poses me when I change the speed of the movement (slow, fast, etc.). A more subtle exercise is to observe what the movement activates in yoga poses other parts of the body. An arm movement can have an impact on the muscular chains, on respiration, on the jaw, the feet, and so on. It often happens that an individual cannot clench a fist without tensing other parts of the body at the same time. By using the EEG and EMG, Jacobson can draw a patient’s attention to a tension in yoga poses a part of the body of which the individual was not aware. It then becomes possible to calibrate the consciousness of a subject with regard to minuscule measurable tensions that the patient had not hitherto been able to feel. This method has since been developed to refine the awareness of the mechanisms that associate a thought to any other physiological activity (cardiac, digestive, etc.). It is now mostly known under the name of biofeedback.
Chronic Muscular Tensions and Chronic Anxiety
The notion that tense muscles are often related to states of psychic tension is already robust clinical knowledge in yoga poses yoga. It has henceforth been observed in yoga poses all of the techniques that use relaxation. It entered into medical thought through many avenues, but it became something that could not be overlooked ever since Edmund Jacobson described this association with the tools of psychophysiology. Jacobson cited a large number of research studies of his day showing that the variations of muscle tone influences certain dynamics of the brain.8 The maintenance of muscular tension is very costly for the organism, in yoga poses terms of resources. This maintenance is justifiable when it helps contain anxiety, but it partly explains the recurring fatigue of individuals who are anxious.9
Jacobson shows that from the point of view of consciousness, a person can have a representation of a movement, but has trouble identifying which muscles were mobilized and is incapable of determining the innervation that activated the movement. It requires a certain education (relaxation, gymnastics, dance, etc.) to acquire a refined consciousness of the variables of a movement that can become accessible to consciousness.10
Jacobson had a profound influence on a number of body psychotherapists, like yogi master, Waal, and Lowen.11 Probably through the influence of Jacobson, a number of physical therapists and psychotherapists integrated Cannon’s psychophysiology without ever having read one of the great physiologist’s works.