It stimulates the central nervous system by blocking the signals in your brain that stop you from feeling sleepy. Your heart beat will increase, the body’s airways will increase allowing more oxygen and blood to be transported. This results in an improvement in energy levels, mental alertness, reactionary times and reasoning skills.
In the work place people may use caffeine to combat feeling physically and mentally tired. Athletes doing training may use caffeine to stimulate their mental and emotional state to allow them to become more motivated to train harder and get better results.
Yes, too much of one thing can be a bad thing. Taking more caffeine can lead to an addiction, which can lead to mood swings, an increase in heart rate, insomnia and anxiety. According to the Mayo Clinic, 400 milligrams of coffee is safe for most adults.
If you are going to used caffeine to aid your training be smart about it, do your homework and get advice from a health professional. If you are an international athlete, make sure the caffeine based pre-workout does not contain substances that would be considered illegal that will lead to a positive drug test.
Not all coffees are created equal, unless you know what amount of caffeine is in your coffee, you are better off using a caffeine based pre-workout supplement.