So, closely following our article The Live Longer Plan, which examined how the body uses different types of fuel to create energy and therefore the best way to fuel in order to become keto-adapted, we now look at the HUGE impact that physical activity/exercise has on how this happens.
Three Ways to Go
The body is able to use one of three different energy systems during exercise.
If we exercise extremely vigorously for a few seconds, such as breaking into a sprint or if our fight or flight response is triggered, we don’t use ATP from cellular respiration. Instead, we rely on producing ATP, the universal fuel, from creatine phosphate of which we have very limited reserves in our muscles. This is called the phosphagen, creatine phosphate or phosphocreatine system.
Its plusses are that it makes energy instantly. Its downside is it doesn’t make very much. That’s why nearly everyone can do three or four press-ups, but some struggle to do more. So while it can be used very effectively to get Mark Cavendish across the finish line in first place in his sprint in a Tour de France leg, we originally developed the phosphagen system to protect us from sabre-toothed tigers.