Throughout this book stress is mentioned or described in relationship to other topics in focus. Stress is likely to influence every client you work with to some degree, and can also be a factor in your health and happiness as a therapist. It is essential that every massage therapist understand stress in order to recognize the benefit of massage and the impact that massage can have on various conditions and diseases, on general health, and on a person’s sense of wellness.

Stress Defined

In the broadest sense, stress is defined as any event that threatens homeostasis and causes the body to adapt. With this broad meaning in mind we understand that stress is caused by any change in external temperature, water intake, physical exertion like that during aerobic exercise, changes to diet, or even positive excitement like that experienced at a sporting event. Physiologists point out that while the reaction of the body to exposure to cold temperature is different from it’s reaction to fighting an infection, and different from it’s reaction to an event that causes anxiety and fear, in one respect all of these types of stress are the same. They all cause the secretion of cortisol by the adrenal cortex to increase. Therefore, physiologists define stress as any event that causes increased cortisol secretion.¹⁷¹

This topic is more specifically interested in stress caused by an event that triggers the flight-or-fight response. The flight-or-fight response is a full-body reaction mediated by the sympathetic nervous system as an inborn, automatic reflex to any perceived danger. It has protected mankind throughout evolutionary history by rapidly preparing the body to respond to a life-threatening event (i.e. animal attack). The problem is that the body can’t differentiate between a hypothetical threat that might be caused by something like an unpaid bill, and a genuine threat where immediate action is required to survive. It is possible for the flight-or-fight response to be triggered multiple times in a day by non-life-threatening events such as sitting in traffic, being late for a job interview, worries about finances, or relationship issues. Furthermore, people are socialized to behave a certain way. You might get the full-body adrenalin rush of the flight-or-fight response when a coworker challenges you at work, but you would be unlikely to act on it. You wouldn’t run away or beat him up. Instead you suppress your physical and emotional responses with muscular, mental, and emotional tension to avoid the embarrassment of acting in a socially unacceptable way.

Stress that triggers the flight-or-fight response could be further broken down based on the origin of the stress or on it’s duration. Stress can be mentally based (i.e., negative speculation about the reaction of your boss to a complaint filed by a customer), emotionally based (i.e., grief over the death of a loved one), or physically based (i.e., pain from a soft-tissue injury can trigger the flight-or-fight response). It can be short-lived lasting a few minutes to a few hours (i.e., You mistake your father standing in a darkened kitchen for an intruder), or chronic (i.e., you are under constant pressure at work and do your best each day to suppress it).

The regular activation of the flight-or-fight response can lead to elevated levels of stress-related chemicals like epinephrine (adrenaline) and cortisol in the bloodstream that remain for prolonged periods of time (sometimes referred to as adrenaline and cortisol poisoning). In this situation, these chemicals become destructive to the body, and lead to stress-related disorders like high blood pressure, heart diseases, ulcers, impaired immunity, and even psychological changes in personality and behavior (i.e., increased aggression or defensive behavior).

<cb4-5><Concept Brief 4-5: Stress>

The Anatomy and Chemistry of Stress

The flight-or-fight response is mediated by the sympathetic division of the autonomic nervous system, which you will remember from anatomy and physiology classes is the part of the nervous system that cannot be controlled voluntarily but operates automatically. It controls smooth muscle, cardiac muscle, and certain glands. It is regulated by the cerebral cortex, hypothalamus, and medulla oblongata and broken into the sympathetic and parasympathetic divisions. The sympathetic division of the autonomic nervous system refers to the part of the nervous system that activates arousal responses during emergency situations or any state of high excitement including non-emergency situations such as might be experienced at a sporting event or during elation or joy states. The parasympathetic division of the autonomic nervous system refers to the part of the nervous system responsible for restoring the body’s resources during non-emergency states of rest (relaxation response).

The Limbic System and Stress

The limbic system consists of the hypothalamus, thalamus, hippocampus, and portions of the cerebrum. This group of structures that encircle the brain stem function in the emotional aspects of behavior related to survival. The thalamus serves as a relay station for sensory information (with the exception of smell) traveling to the cerebral cortex. It also interprets sensory impulses related to pain, temperature, light touch, and pressure. It provides some function related to processing emotion and memory. The hypothalamus is involved in homeostatic regulation of the autonomic nervous system related to body temperature, water balance, appetite, sleep, and key emotions like fear and pleasure. It receives impulses from sound, taste, smell, and from neurons monitoring the internal environment of the body. It is the primary connection between the nervous system and endocrine system. A stressor causes a cascade of rapid physiological reactions that facilitate the flight-or-fight response.

Physiological Reactions in the Flight-or-Fight Response

When a threat is perceived by the limbic system it stimulates the hypothalamus causing the hypothalamus to release corticotrophin-releasing hormone (CRH) into the blood stream. CRH reaches the anterior pituitary gland and causes it to secrete adrenocorticotrophic hormone (ACTH) into the blood stream. ACTH circulates to the adrenal glands and causes them to release epinephrine (adrenaline) and cortisol into the blood stream, which then circulate throughout the body to stimulate a range of responses in different body tissues. It is interesting to note that current research has discovered that ACTH not only stimulates the secretion of cortisol but also is a peptide related to learning and memory. We can speculate that ACTH served an evolutionary purpose in helping early humans learn to avoid danger. <fig4-9>

Cortisol is a hormone that promotes the breakdown of proteins to form glucose to fuel muscles. The action to mobilize fuels has some important implications for health. For example, a person who is sick or undergoes surgery catabolizes (breaks down) considerable amounts of body protein, while a child exposed to prolonged and severe stress experiences retarded growth. Cortisol enhances vascular reactivity, decreases white blood cell accumulation and fibroblasts in an area of injury to reduce inflammation, and has a powerful anti-allergenic action. Cortisol can also reduce the number of circulating lymphocytes in the blood stream. It decreases both antibody production and the activity of T cells explaining why people are more prone to colds when they are stressed.

Epinephrine plays a central role in the sensation of physical and mental energy associated with the flight-or-fight response. It sharpens the senses, increases the speed of reflexes, and boosts muscular strength. It triggers many of the responses that rapidly prepare the body for a threat like increased heart rate. The flight-or-fight response produces a range of rapid changes in the body to ensure the body can respond to a threat.

• The pupils of the eyes dilate to let in more light to sharpen vision.
• The rate of the beat and the force of the heart’s contractions increase, while blood pressure rises. This ensures that blood is pumped effectively to large muscle groups and to the brain so that the body can respond with maximum effort.
• The blood vessels of the skin and viscera constrict to ensure adequate blood flow for skeletal muscles, the heart, and the lungs. Blood to the hands and feet is restricted to ensure that large quantities of blood would not be lost in the event these extremities were severely injured fighting or fleeing.
• Rapid breathing occurs and the bronchioles dilate to allow for the faster movement of air in and out of the lungs.
• Blood sugar levels increase as glycogen in the liver is converted to glucose to supply the body’s energy needs.
• Muscle tone increases and the body’s reflexes become hair-triggered allowing quicker responses.
• Non-essential processes such as the muscular movements of the gastrointestinal track and digestive secretions are slowed or halted.
• Perspiration increases to cool the body, which becomes hotter due to a rise in metabolic processes.

When the body is in a state of homeostasis the sympathetic nervous system counteracts the effects of the parasympathetic nervous system just enough to carry out normal processes requiring energy. When the body experiences chronic stress the sympathetic system dominates the parasympathetic system contributing to or causing many diseases and conditions (Fig.4-10). <fig4-10>

<cb4-6><Concept Brief 4-6: Flight-or-Fight Response