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May 2017
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Effort and recovery play a key role in everyone’s life. In fact, everyday experiences seem to confirm that life takes place between the poles of sleep and wakefulness, activity and passivity and tension and relaxation. The various dimensions of a person’s psycho-physical state, such as excitement and inhibition, pleasure and aversion and tension and relaxation, can be reduced to two fundamental conditions: activation and relaxation. Activation and relaxation, from a phenomenological point of view, are considered distinct objects of research, even though they are believed to be the opposite poles at the ends of a continuum.


The methodological and theoretical development of psycho-physiology is closely related to the study of activation: the main aim of this discipline is to study the relationships between psychological states and physiological processes when excited. The theoretical meaning of activation has been developed through concepts of stress, arousal and emotion. 
In very few words, excessive activation is considered to be the main cause of psychosomatic illnesses related to stress. The body is equipped with complex, functional systems which adapt to variations of internal and external conditions so as to maintain a stable equilibrium (homeostasis). The state of activation occurs whenever the body finds itself threatened by something dangerous. From this point of view, activation is the general reaction of a system which must deal with changes to pre-existing conditions. Stress coincides with a state of maladaptive hyper-activation and, in fact, the negative connotation of stress, that we know of today, derives from the fact that a prolonged and/or excessive activated state naturally leads onto a phase of exhaustion or failure, often associated with a pathological condition of the body or mind.

There are two analytical levels of the psycho-physiology of activation:

  • physiological
  • psychological-behavioural.

Different activation processes can thus be described:

  • the process which regulates the sleep-awake cycle;
  • the process which regulates general activation (tonic);
  • the process which controls localised activation (phasic);
  • the process which picks out relevant information from irrelevant and distracting information (selective attention).

The neurophysiology of activation and stress

The response to psycho-physical activation is defined as a series of transformations (physiological and behavioural) which happens when one is being stimulation. The stimuli, which induce a state of stress (stressors), are encoded by different sensory organs which serve as transformers, changing physical events into electrical signals. The encoded information can then reach and activate the reticular formation of the brainstem.

This neural structure attributes the quantitative component of activation, which is determined by the stressor. The common excitatory action of this structure also reaches the so-called limbic system, the function of which is to attribute the qualitative and emotional component of the stimulus. Through this complex system, information about the stressor, which is characterised by a specific intensity and quality, is transmitted to the hypothalamus and the associated prefrontal cortex.
The hypothalamus is the centre of neurovegetative regulation (which regulates the heart muscle, the blood vessels, the gastrointestinal tract, the exocrine glands, and so on) and neuroendocrine regulation (which controls hormonal functions). The prefrontal cortex, on the other hand, controls somatic-motor responses, such as flight or attack reactions.

The physical signs of activation are:

  1. breathing fast
  2. increased consumption of oxygen
  3. increased heart rate
  4. reduction of cutaneous resistance (caused by an increase in perspiration)
  5. increased skeletal muscle tone
  6. peripheral vasoconstriction
  7. increased electroencephalogram desynchronisation (EEG), that is, increased frequencies and decreased amplitudes of brain waves.


Relaxation can, psycho-physiologically, be defined as:

  • the opposite, or absence of, activation;
  • the psyco-physiological state which lies at one end of the activation-deactivation continuum.

Therefore, relaxation cannot be considered to be (what it is called in activation research) a resting phase.

Instead, relaxation can be defined as a series of characteristic reactions which are registered on a physiological level, such as:

  1. breathing slower and regulating respiratory cycles
  2. reduction in oxygen consumption
  3. slower heart rate
  4. increased cutaneous resistance
  5. decreased skeletal muscle tone
  6. peripheral vasodilatation
  7. increase in EEG synchronisation, that is, there is an increased percentage of alpha waves.

The physiological feature of the reaction of relaxation fundamentally consists of a general lowering of the intensity of excitement of the sympathetic component of the automatic nervous system and an increase in the activity of the parasympathetic component, which can be seen via:

  • changes in autonomic functions (low blood pressure and heart rate, decreased pupil size, reduced sweating and increased motor and secretory activity in the gastrointestinal system).
  • central nervous system changes (increased synchronisation of the EEG and hypotonia of skeletal muscles).  
  • changes in behaviour, experiences and consciousness (inactivity, stupor and a hypnagogic state).

Complex, physiological reactions which occur during relaxation must not be confused with those of sleeping. The series of responses which make up a state of relaxation are the opposite to those that occur during reflex reactions, such as flight or attack reactions. Thus, relaxation can be recognised by a reduction in the sympathetic nervous system excitation.

On a psychological level, relaxation is manifested through:

  1. an individual feeling of tranquility and relaxation
  2. decreased alertness
  3. noticeable indifference to internal and external stimuli

Neurophysiology of relaxation

During a state of relaxation, there is a reduction in reticular formation activity and a balance between the reticular system (intensity) and the limbic system (emotional-quality).

Lastly, a state of relaxation does not involve reducing physiological functions, rather it involves maintaining the balance of the interactions of such functions.


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