Efficiency and economy is vital to your ultimate success as a runner, so it's worth spending some time examining these two elements a bit more closely. The women of the Kikuyu tribe in Kenya provide an execllent lesson of optimal body position and movement that can be applied to athletes who wish to improve their running efficiency and economy, and get faster.
What Is the Energy Cost of Running?
We know that the energy cost of running is clearly connected to the generation of muscular force into the ground, as reported in the journal, Nature. In fact, we discuss this almost daily in our lab at Pursuit Athletic Performance. Think of it this way: It's what is often known or referred to as the "bouncy ball" effect. If I were to take a bouncy ball and throw it to the ground, the harder I throw it, the faster it will come off the ground and the farther it will travel back into the air. The bottom line: Assuming a runner is carrying "X" percent body mass, energy expenditure to run at any pace would be roughly equal to "X."
The energy cost of running is impacted by the way we run. One way to think about running mechanics is to see that when we run, we basically turn our bodies into an upside down, or inverted, pendulum. In case you have forgotten high school physics, Robert Kunzig describes a pendulum in "The Physics of...Walking," which appeared in Discover magazine, as:
"a device that transforms kinetic energy of motion into gravitational potential energy and back. As it moves through the bottom of its arc, the pendulum's velocity and thus its kinetic energy—mass X velocity squared divided by 2, or mv2/2—reach a maximum. At the top of its arc, the pendulum slows to a stop, but at that point the potential energy—mass X gravity x height—is at its peak. As the pendulum falls back down, potential energy is converted back to kinetic energy. In a good pendulum the conversion is close to 100 percent, with only a bit of energy lost to the friction of moving through the air and that of the bearing from which it is hung. One nudge, and a pendulum keeps swinging a long time."
What does this have to do with how efficient and economical we are as runners, and these women of the Kikuyu tribe in Kenya?
What Runners Can Learn From the Kikuyu
Let's take a quick look at who these women are, and why what they can do is so important for runners. The Kikuyu women are well known for the unique way they carry heavy loads on their heads and back as they amble over the roads and trails of their northern central Kenyan countryside. They carry their loads by strapping the sack that hangs on their backs across their foreheads. Incredibly, they often end up with permanent changes to the front of their skull due to the load inherent in carrying those sacks.