What causes the breathing rate to increase?

usually any type of physical activity...such as lifting weights or running and jogging..if you want a more scientific response then here it is....a heightened breathing rate is caused when the body detects that you are doing something (lets say you just started running) you will breath normally for a little bit but then your body starts using more and more oxygen to keep your arms and legs going...and your brain detects this and in creases your breathing rate as to get more oxygen into your blood stream to power your body more efficiently...i hope that answered your question..if not then comment back