Everyone has to cope with stress in life. Stress is something one cannot avoid whether it is positive, negative, mental, physical or emotional. It is important to note that stress depends on many variables and can affect each individual in a different way. Athletic performance is improved by stress; performance is usually very weak without intensity. This has been proven in many ways such as with the inverted U theory, the zone of optimal functioning and the catastrophe theory. .
Although we do not all respond to stress in the same way, our bodies all undergo certain physical changes. These changes take place in order for our body to prepare for a flight or fight response. More blood is made available for our large muscles by shutting down the digestive system. This can cause nausea due to stomach acid build up. Blood is diverted from the surface, which explains why if you get cut during a game you often do not bleed until afterwards. Under stress the body produces adrenaline and other enzymes such as horadrenaline, epinephrine (heart stimulus) and cortisol, which provide powerful, quick busts of energy that sometimes results in superhuman feats. .
The "Inverted-U Theory" presented by Yerkes-Dodson in 1908 states that with the increase in intensity or stress results in matching improvement in performance. After a certain point, the body can no longer handle any more stress, and it begins to hinder performance. This is shown with and inverted-U shaped function relating stress and performance. Too much or too little stress will hinder performance. For optimal performance, you need mid-level stress. Tool little stress calms the athlete down and causes and lethargic affect on the athlete. Too much stress will hinder concentration and cause unforced errors in performance. This graph stretches, compresses and shifts depending on the sport. Less stress is optimal for tasks that require a lot of concentration and more fine tuned motion such as golfing or pitching.