Good paper, I skimmed it and it seemed very informative. One thing for most people who are reading is that at high intensities you are always using all 3 forms of energy production. It might help to think of it on a time scale. When you don't need energy quickly (now while reading/typing) you are getting your energy from the electron transport chain. As intensity increases you need energy quicker so you need to utilize more forms of energy production. At the highest intensity (which can only be kept up for around 20 seconds, as stated in the paper) you are using the fastest form (creatine/atp) along with glycolysis and electron transport chain. What dictates when to switch over and include another form of energy is the exercise intensity. Even during normal,low intensity, movements such as breathing I'm sure you are utlizing (albiet very small amounts) of creatine/atp.
