70 Chapter 4: Stress Management and Sleep Individual Zones of Optimal Functioning (IZOF). The individualized zones of optimal functioning (IZOF) is yet another theory, currently growing in popularity. This theory tries to describe the relationship between stress and performance and suggests that each person has a unique zone of optimal stress, rather than a specific point as suggested in the inverted-U model (Hanin et al., 1986). Additionally, this optimal zone of stress doesn’t always occur at the midpoint of the stress continuum but rather varies from person to person. The IZOF theory is illustrated in Figure 4.3. Figure 4.3. Relationship Between Stress and Performance According to the IZOF Theory Stress Response There are three stages to the stress response: alarm, resistance, and exhaustion (Selye, 1974). The first stage of the stress response is called the alarm stage or the fight-or-flight stage. In the alarm stage, the hypothalamus stimulates both the pituitary gland and sympathetic nervous system (part of the nervous system responsible for providing a rapid and involuntary response to dangerous or stressful situations). The pituitary gland responds by releasing adrenocorticotrophic hormone (ACTH), which in turn stimulates the adrenal glands. The adrenal glands respond by releasing the hormones cortisol, epinephrine, and norepinephrine into the blood. Collectively, these hormones and the sympathetic nervous system produce a heightened state of physical awareness. Some of the physiological responses to stress include increases in blood pressure, heart rate, respiratory rate, blood flow to the muscle as well as activation of the sweat glands (Johnson & Morris, 2012). These responses are depicted in Figure 4.4.
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