Experiences of stress may change the way a person thinks about everything, they way they behave and their pattern of physiological activities. The changes under certain circumstances can lead to the increase of risks associated with psychological, social and physical ill-health and at times behaviours that are inappropriate (Houdmont and Leka, 2010, p37).
Stress can be defined as the non-specific response by the body as a result of any demand made on it. Demand in this case is defined as a stressor which may arise from a stimulus or an event. Stressors come in many different ways and they range from time pressure, extreme pressure, and extreme temperature to physical assault. When an individual is exposed to such a stressor, a physiological stress response occurs. The response can be measured through observation by different measures such as dilated pupils, increased heart rate and increased blood pressure according to Hosek, Kavanagh and Miller (2006, p23).
Physiological manifestations of stress are identical regardless of the type of external demand but its effect on performance varies among individuals. The effect on performance ranges from physical impairments and cognitive reactions. Stress-performance relationship models indicate quite different scenarios. There is U-shaped and negative linear stress-relationship models. In the U-shaped model, performance improves when the stimulus reaches a moderate level and decreases when the stimulus levels increase beyond the moderate levels. Although this is the case, individual differences that exist may alter the shape of the curve. According to a research done, evidence showed that an inverted-U relationship exists in the industrial sector especially on job performance. In a negative linear relationship, stress regardless of the level reduces work performance through draining the person’s energy, time and concentration.