Homeostasis is the process by which the internal environment of the body is kept relatively stable despite changes in the environment. Your body is able to adapt to several different conditions. When exercising you become a little bit acidic because lactic acid accumulates in your tissues (especially muscles) due to glucose metabolism (to produce energy), because of this, your breathing becomes faster to eliminate CO2 which also causes acidity. Your heart rate increases in order to pump more oxygenated blood around the body. Another factor is heat, because your body uses energy up, body temperature is increasing and overheating is prevented through sweating which cools your body down. When you sweat, you lose some water, this signal is received by the brain's thirst centre and so it makes you feel thirsty and want to drink.
The blood glucose level will increase during exercise if there is not enough insulin. Muscles hold enough energy for a short amount of exercise. After that, they rely on increased blood supply to deliver oxygen, blood sugar and other nutrients to maintain more energy. Your body burns the sugar in your blood, and then tries to regain more from your liver to supply stored glucose to keep up with energy levels. As you warm up, your muscles start to try finding nutrients to make energy. Glucose carried in your blood and delivered to the muscles is an energy supply, as are free fatty acids, a type of lipid carried in blood that provide energy when glucose is low. Using energy during exercise helps balance high blood sugar and provide fuel at the same time. As blood flow to your muscles increases, the energy supplies increase as well.
During exercise, the muscle cells respire more than they do at rest. This means, oxygen and glucose must be delivered to them more quickly and waste carbon dioxide must be removed more quickly. This is achieved by increasing the breathing rate