Relaxation

Physical Characteristics

While the stress response is characterized by the fight-or-flight mode of the body because of an activation of the sympathetic nervous system, during relaxation states, the sympathetic nervous system is damped and as a consequence the parasympathetic nervous system exerts more influence on the body systems (rest-and-digest mode). The assumption that sympathetic and parasympathetic nervous systems always act antagonistically is an oversimplification; in fact, both systems are connected through a fine-tuned mutual interaction.

Neuromuscular changes. The relaxation response of the neuromuscular system is mirrored by a reduction of muscular tension and a decrease of motor reflex functioning. Electromyographical methods (EMG) may be used to measure muscle tone. Muscular tension is controlled from supraspinal centers, or neurons located in the brain stem. That means that top-down processes such as perception and thoughts are closely linked to the neuromuscular system, which explains why mental strain/stress becomes manifest in muscular tension and hardening.

Cardiovascular changes. Cardiovascular changes of the relaxation response include vasodilatation, as well as a minor/slight reduction of heart rate and blood pressure. In addition, heart rate variability (HRV) has recently become an important parameter in monitoring vegetative states.

Peripheral vasodilatation leads to a better blood supply of the skin, which is usually accompanied by a sense of warmth. In autogenic training, an autosuggestion-based relaxation technique, this effect is applied in one of the classical exercises (warmth in the limbs).

Effects of popular relaxation techniques (e.g., autogenic training, meditation, and biofeedback) on heart rate and blood pressure are heterogeneous, and thus neither of them seems to be an appropriate parameter to measure the relaxation response.

The heartbeat of a healthy subject does not work exactly as a metronome. In fact, slight [Page 948]variations of the heart beat (because of a variety of mechanisms that influence the autorhythmicity of specialized cells in the myocardium) are a sign of health, or “heartiness.” These physiological fluctuations of the heartbeat are called heart rate variability (HRV). Decreased HRV can be understood as a marker of vulnerability to stress, reflected in impaired cardiovascular regulation.

Respiratory changes. Accelerated and shallow breathing (hyperventilation) are typical stress symptoms. In contrast, regular and deep respiration is a sign for a relaxed state. Accordingly, many relaxation methods such as autogenic training, progressive relaxation, or meditation make use of breathing exercises. In particular, abdominal breathing is a common and effective practice to become quiet and calm and reduce stress. In music therapy, the entrainment between respiratory rate and music is commonly used, for example, when working with comatose patients.

...