10/05/2011 10:50 am ET | Updated Dec 05, 2011

A Runner's High

Susan can run four laps on a track (one mile) in four minutes and 30 seconds. What is her average velocity?

"Six meters per second!" Wrong.

The correct response? Zero.

Our teacher explains, with a gleefully sardonic smile, the vector nature of velocity. "Susan could have run the mile in three minutes flat, or two, or one, for all we care. Her velocity is still zero; she's not getting anywhere."

My friend Cassidy and I exchange alarmed glances. As high school runners, we cannot allow Mr. Barrows' blasphemous propaganda to endure. That would be tantamount to playing Judas to our sport. Instead, we refuse to accept that 10 miles around White Rock Lake, uphill sprints at Flagpole, and five-mile BAEs all boil down to zero frickin' meters per second.

We are Highland Park girls cross country. 138 strong, we roam the hallways proudly with our 32-ounce Camelbaks. We've developed a set of defining marks: tan lines comparable to Blue Bell's Great Divide, a helpless inability to sit still in class (because dammit! we need to pee), and an appetite equivalent to a that of a grizzly bear post-hibernation.

Our workouts are kind of like a pizza dish. 10-mile Tuesdays form the trusty old sourdough crust, the fundamental aerobic endurance onto which all other ingredients are piled. On the other side of the pie, the garnishes: mushrooms, pepperoni, sausage, pineapple and ham, bell peppers. These are the "fine-tuning" uphill repeats, core work, and starting sprints. In between, you'll find tomato sauce (recovery Thursday -- a buffer against the loud flavor of the toppings) and, mostly importantly, the cheese -- the "best aerobic effort" run. These are training segments that usually span five miles, covered at a tempo right under the threshold of race pace. A pizza is not a pizza without the cheese; a runner is not a runner without the BAE run.

"Ann, why in the world would you choose cross country?" my non-runner friends ask, "It sounds like corporal punishment more than anything else." And sometimes I agree with them. Recall the entire month of August. My recreation of choice required that I meet with the team at four in the afternoon every day to train. The mercury read 108, 106, 109, 110, 104 ... Meanwhile, the rest of the sane human population found solace in its plasma-screened igloos.

So why does Susan choose to compound physical exertion with climatic brutality when Don and Sally are perfectly content with vegetating in front of the latest episodes? For one, there's nothing like the rush at the finish of a hard workout. It's a state of light-headed, clear-lunged euphoria that engenders goofy behavior (read: Lady Gaga impressions, curly fries stuck up nostrils, Oreo cookies slingshot through car windows).

Everyone knows about the runner's high. It's caused by the production of a fatty acid called anandamine, which functions similarly to the THC found in marijuana. The lipid component relieves pain, stimulates pleasure, and leads to "an openness to experience," "increased appreciation of nature" and a "boost in empathy." Futhermore, anandamine works as a part of a biochemical chain, triggering the production of those notorious endogenous opiates known as endorphins, which pretty much have a dance party in the runner's prefrontal cortex so she isn't a miserable wreck as she's surging that last 400 meters.

Basically, we are in so much physical pain that our bodies must compensate by excreting specific hormones that, in addition to blocking out the bodily torment, conveniently leaves us giddy like a five-year-old. Alas, my faith in science is again restored. Physics, move out -- biology's stealing the show.