There is an increase in blood supply as your body is working "overtime”. The blood supply has to increase because it has to go to the parts in your body which you are exercising the most e.g. If you are taking a run, the blood supply will increase because your legs will need more energy, therefore there will be more blood circulating your legs than normal because you are overworking them. Your muscles and all your body organs need more energy and oxygen; this is because your body is working more than usual. Your body needs to do many things such as sweat, which helps you cool down, and to get energy to all of your cells in your body to help you carry on exercising, if your body didn't do this, and then you wouldn't be able to carry on exercising. During acute exercise your muscle pliability increases which allows a greater range of movement which helps reduce injury. Acute Exercise will cause muscle fibre tears. This is generally known as micro- trauma. The myosin heads and the actin filaments will be pulled from the myofibrils. This damage will cause a release of chemicals that cause the soreness after your period of exercise. The chemicals released also stimulate repair and growth in the area to rebuild the tears in the muscle.
ATP is a molecule in the body that is used to break down energy. There are two main energy systems Aerobic and anaerobic. When energy is needed, ATP is broken down into ADP (Adenosine Diphosphate). This process breaks the high energy Phosphate and so releases energy for use in the body. The body must be able to adopt to the change in physical activity. The first system that we use is the ATP-PC system. This produces Phosphocreatine which is only used for short durations of up to 10 seconds. The system neither uses oxygen nor produces lactic acid and is thus said to be alactic anaerobic. This system is used for very short, powerful movements like a golf swing or a 100m sprint. Once all the energy production from the breakdown of ATP has been used we have a potential problem. We therefore require stores to be replaced in the form of an endothermic reaction, to resynthesise ATP. Once our CP stores are depleted the body resorts to stored glucose for ATP. The breakdown of glucose or glycogen in Lactic Acid system results in the production of lactate and hydrogen ions. The accumulation of hydrogen ions is the limiting factor causing fatigue in runs of 300 metres to 800 metres. After the entire PC is used up the body goes into the aerobic energy system. This system utilises proteins, fats and carbohydrate (glycogen) for the resynthesising ATP.
Before we start to exercise our heart rate increases slightly in anticipation of the activity ahead. It is mediated through the releases of neurotransmitters called epinephrine and norepinephrine also known as adrenaline and noradrenaline. This is known as the Anticipatory rate. After the initial response our heart rate increases in direct proportion to the exercise intensity until a maximum is reached. Systolic BP increases in direct proportion to increased exercise intensity. Diastolic BP changes little, if at all, during endurance exercise, regardless of intensity. Vasoconstriction and vasodilatation occur as the oxygenated blood needs to be diverted to the working muscles and reduce blood flow to less important systems e.g. Digestive System.
When you are exercising your respiratory system responses by your breathing rate increases and you start to breathe heavily, this happens because your muscles need more oxygen so you breathe deep and quicker so a supply of oxygen can get to the muscles, also when you finish exercise your breathing rate will decrease and start to recover. Another response from the respiratory system is the tidal volume, which increase as a response to exercise this is because the muscle needs an...