17. I use the bathroom right before I start, so why do I have to pee mid-run?The urge to detour into the bushes can happen for a couple reasons, says Craig Comiter, M.D., associate professor of urology at Stanford Medical School: As your heart pumps blood more rapidly around your body, your kidneys may produce more urine, especially if you were well-hydrated prior to your run and you drink during it. You may also be dehydrated, and the concentrated urine in your bladder may give you that gotta-go feeling; or, due to a slightly weak sphincter combined with the jostling of running, a bit of urine may leak through the bladder and stimulate the urethra, making you wish you could cross your legs while running. (Pregnancy causes the need for more pitstops, too.)
Running Rx: Take a pee break, says Dr. Comiter. If it happens a lot, schedule a pit stop at a urologist's office.
18. Why do I feel like a genius after a run?Perhaps the biggest benefit of a great 10K is that, post-run, you're sure you could score 1,600 on the SATs (2,400 if you're under 25)—or at least improve. "Running increases levels of positive neurotransmitters, like endorphins; norepinephrine, which is responsible for alertness; and serotonin, which helps regulate mood," says Fitzgerald. "Plus, running puts the brain in an 'alpha-wave' state, which is associated with feelings of calmness and well-being." A handful of studies have documented that moving your feet correlates with improving your brain; two conducted at the University of Illinois found that 30 minutes of exercise resulted in up to a 10 percent improvement in cognition, or being more effective in processing a problem or situation. Maybe that stellar score isn't out of reach.
Running Rx: If you really have to ask, maybe you should go for a run.
19. Why does my nose run as fast as my feet?Don't chalk it up to empathy. A runny nose, a condition called exercise-induced rhinitis, is most likely due to the increased air flow; as your breathing rate increases, your nose kicks into hyperactivity. "Cool and dry air—or both—have been shown to increase secretions, similar to what we see in exercise-induced asthma," says James Sublett, M.D., allergist and professor at the University of Louisville School of Medicine in Kentucky. If you're self-conscious about your drippy schnoz, know you're not alone: A 2006 study, published in the Annals of Allergy, Asthma & Immunology, surveyed 164 exercisers and found that 40 percent had a runny nose while exercising inside, and 56 percent had one outside.
Running Rx: If your runny nose is a serious issue—it continues to run long after your workout and into your very important presentation—you might consider taking an antihistamine, such as Claritin or Zyrtec, or using an over-the-counter saline nasal spray prior to your run. Otherwise, stuff your pockets with tissues, and perfect your farmer's blow.
20. At the end of a long run or race, why do I question the meaning of life?I had a client who told me at the end of a marathon, she could see the Virgin Mary," says Manuel Villacorta, M.S., R.D. "She felt like she was dying." One of the prominent symptoms of hypoglycemia, or low blood sugar, is angry, depressing thoughts. When your body isn't receiving the glucose it needs to perform, your brain, the air-traffic controller of your body, springs into action, sending messages—Why are you out here anyway, stupid?—for it to shut down and self-preserve.
Running Rx: The day before a long run, eat three nutritionally sound meals and make sure your body's fuel tank is topped off before you head out. During the run, take in about 30 grams of carbs every 30 to 40 minutes. Before you head out, line up your answers to the inevitable questions (or at least draw up your will).race.