Exercise: Why Starting Up Is the Hard Part

Runners will tell you, the first half mile is like running through the flames of hell. Swimmers will tell you, the first five laps are like swimming in Jello. Soccer players will tell you, for the first five minutes on the field, there just isn’t enough oxygen to fill your lungs. Then, something happens, and the pain turns to pleasure. What exactly is happens inside that body is nicely explained in this Washington Post piece by Howard Schneider.
"As movement increases," Schneider writes, "capillaries leading to the muscles start to open
and carry the blood where it is suddenly demanded. Your heart begins
not just beating faster to accommodate, but also increasing — perhaps
as much as doubling — the amount of blood it pushes out with each
beat. The muscles become a sort of pump to help this happen: The
contractions that lead to motion also help push blood back to the heart
through the veins."
That’s the big picture. Schneider also drills down to the high school chemistry component: "The substance that allows your muscles to contract is called adenosine
triphosphate, or ATP. Your body has several ways to synthesize it using
such materials as creatine, lactic acid, glycogen and a bunch of
enzymes, all present in the body. A couple of those methods can be
tapped quickly to support an increase in activity — when you pop up
the stairs from the company lunchroom, for example, or run a sprint." But, Schneider says,"those initial energy sources can keep pace for only the
first few minutes. After that, the body turns to its real energy
powerhouse: aerobic glycolysis, a process in which glucose (the basic
sugar that the body uses for fuel) is broken down with the aid of
oxygen to produce ATP. It’s a very productive system, by some estimates
yielding 30 or more molecules of ATP for each molecule of glucose.
That’s why it can sustain all those crazy bouts on the elliptical, not
to mention a marathon run."
Read more about what’s so hard about the hardest part of exercising, in the Washington Post.