To achieve a training effect, the body must be overloaded, that is, exposed to a physical stress which is greater than that encountered in everyday living. The response to this training stress is catabolism, the breakdown of metabolic fuels or tissues. When muscle is the tissue being studied, the phenomenon is called Exercise Induced Muscle Damage (EIMD). Following this catabolic response, the tissues react by adapting and becoming better suited to coping with the imposed stress; this adaptation is known as anabolism, and involves tissue growth. With training, the anabolic effect is excessive, causing the tissues to grow stronger, a process called supercompensation. Adaptation to exercise (a physical stress) can be understood through the principles of the general adaptation syndrome (GAS) first described by the Hungarian endocrinologist Hans Selye in the 1930s with reference to psychological stress. Plotting time against resistance to stress (Fig. 2.1a), the GAS consists of three phases. The first is the alarm phase as the body reacts by preparing its ‘fight or flight’ mechanisms, releasing hormones such as adrenalin and cortisol. Phase two is the resistance phase, when the body tries to cope with the imposed stress. The final phase is exhaustion, when the body has depleted its coping mechanisms and may suffer from pathologies such as high blood pressure or ulcers, for example.