I've heard it theorized by the bro scientists that we have an internal meter that holds potential "energy" for all physical activity, and that meter must be exhausted, or at least reduced, on a daily basis. For the modern man, this is commonly done by walking, running, yoga, lifting weights, manual labour, etc.
For most of history, the practice of exhausting your "activity meter" was not a decision of deliberate intention but rather a decision of necessity and survival. (Ie. chasing food for hours or days, running from predators, etc.)
The theory goes on to suggest that the consequences of failing to exhaust your activity meter through physical expenditure is an emotional outburst. If the meter overflows without access to the proper channels it will inevitably be expressed as an emotional meltdown over trivial problems. (Ie. road rage, long line at the store, etc.)
In North America in 2017, our lives are ruled by cutting edge technology while our bodies are stuck running on operating systems from thousands of years ago. Our suburban version of stalking prey for 3 days is running 10k's in fluorescent orange and Katy Perry in both ears.
#ExerciseLikeCaveMen #StrongBodyStrongMind #TheModernMan