"Performance will improve as arousal increases until it reaches a point where optimum performance is achieved, and arousal is at its optimum level. If arousal increases beyond this point, performance will begin to deteriorate." 

"The catastrophe theory suggests that because the athlete went beyond the optimal point, his dramatic decline in performance."

This shows a different view to the inverted-U theory which suggest that there is a gradual reduction in performance. The catastrophe theory can also be seen in Yerkes-Dodson law this would be interpreted in this law because if an athlete find a task easy once you have reached optimum levels of arousal they become demotivated to keep performing at that level at an easy task resulting in a complete collapse in performance as shown in the catastrophe theory.         

"Stress is defined as a substantial imbalance between demands [physical and/or psychological] and response capability, under conditions where failure to meet that demand has important consequences."

This shows that when individuals become stressed they have the inability to cope with the demands that they perceive to be too challenging for them to handle. From this it can be said that when an individual's anxiety levels become too great then they start to be unable to cope with the situation. An individual would become too nervous to be able to complete because that's a personality trait they have and they would be worrying about everything. This cognitive anxiety has become so great that it has lead to them becoming stressed as they are unable to cope with the demands that the situation shows. These demands are known as stressors. These stressors are how individuals perceive the threat of the demands Woods (1998) suggests that some of these stressors that we may perceive a threat are those which threaten our self-esteem, cause personal harm, creates uncertainty (fear of the unknown), creates frustration and creates pressure. These stressors can be internal stressors, external stressors, personal factors and occupational factors. Internal stressors come from within the athlete this is supported by Hathaway (n.d) says that:

"Internal stress is generated by your mind, both unconscious and conscious; it may be triggered by past experiences, present conditions, and expectations of future situations."

(Hathaway, n.d).

From experiences of internal stressors and athlete would start to have a pessimistic attitude, low self-esteem, lack of assertiveness and self-criticism (Len, 2009). This shows that an athlete that was once highly motivated for success and optimistic about achieving their goals, from suffering from stress is now demotivated and pessimistic. This is down to this athlete being unable to control their anxiety in stressful situation. When an athlete suffers from stress they would normally take themselves out of that environment for a couple of months as this would reduce their anxiety levels being away from the situations. Whereas external stressors are created by external situations (things in our environment) these can be the work you are doing as well as relationship that have the most impact of external stressors (Hathaway, n.d). Also Gill (2013) suggest that personal factors are people we spend our time with like family as well as being how financially secure and individual is, Gill (2013) also suggests that occupational factors are the jobs we do and the people we work with. Within sport these factor could be the people athletes work with like coaches or teammates as well as performing in a full stadium or venue, these could lead to stressors occurring.

From this there can be two types of stress, these two types of stress are eustress and distress. Singer (2013) suggests that negative stress is called distress and this comes from the feelings of your well-being threatened, whereas Perry (2012) suggest that eustress is good stress that brings positive aspect to ones life. This implies that there is a positive type of stress and a negative type of stress. Where the an athlete would use eustress to motivate themselves and improve performance, distress would decrease performance as this stress comes from high levels of anxiety which affects the arousal level of the athlete.         

The stress process is a sequences of events that will lead to a particular end, it consist of four interrelated stages which are shown in the image (left) (Weinberg and Gould 2011). in the first stage of this process there is some kind of demand placed upon an individual. This demand can either be physical or psychological, like when a parent puts pressure on a young athlete to win a race. The next stage is how an individual perceives the physical or psychological demands. this would be different in every athlete as not everyone's perception is the same. The third stage is based on how an individual responds the these demands looking at their arousal level of the body and anxiety, this could be faster heart rate, sweaty palms and feeling sick. The fourth stage looks at the athletes behaviour whilst under stress, whether they can cope or if the increase in anxiety affects their performance. It then goes back round in a cycle to the beginning stage (Weinberg and Gould, 2011). Fullerton (2010) suggest that athlete tend to suffer from more stress than non-athletes this is because athletes are required to balance part-time work, practice and games as well as family pressures.    

For an athlete being able to cope with stress is vital to performing to a high standard consistently. For an athlete to get the best results they need to try different coping mechanisms as by doing this they can get the one that works best for them. A coping strategy looks at how an athlete changes their behaviour, thoughts and emotions before competing. An athlete that was once uptight and nervous before an event that has changed their thought process for the start of an event and now doesn't think too much about what could happen could come across as more laid back and relaxed this is how they have coped with the stress involved in that environment. This athlete's coping strategy is to control their thought process better Staroversky (2012) suggest that you can also use attentional focus strategies, emotional strategies and behaviour strategies to help cope with stress.