During periods of prolonged physical or mental exertion, the nervous system is more active than normal and adrenaline production is raised. This leads to symptoms similar to those experienced in a flu-like illness, such as aches and pains, headache, sweating, feeling hot and cold, chest tightness and sore throat. If a person experiences these symptoms after activity, they may reduce or avoid activities, as they may believe that they are coming down with flu or a cold. Limiting activity can perpetuate the symptoms and lead to a further reduction of fitness and muscle strength.
