10. Why do my bending knees sound like Rice Krispies when I walk down the stairs?Snap, crackle, pop? Crepitus, the medical term, happens when cartilage, the connective tissue between bones, starts to age, says James Wyrick, M.D., orthopedic surgeon and associate professor at the University of Cincinnati in Ohio. We all start life with quiet, smooth cartilage between our kneecaps and thigh bones, but over time, it becomes gray and old and doesn't regenerate; most people older than age 30 have some mild crepitus. Weak quads or a tight IT band can pull the kneecaps out of alignment and exacerbate the wear and tear.
Your knees pipe up when they bend past 30 degrees because the kneecap tracks into a groove in your femur—that is, cartilage-weak bone grinds into cartilage-weak bone. "The intensity of the pressure and the different contact points in the groove make the noise," says Dicharry.
Running Rx: "Cracking knees may lead to problems down the line, like arthritis," says Dicharry. Minimize that chance by strengthening the muscles that control the hips and knees, and keep your lower half in alignment, such as clamshells for the hip; squats for the knees (runnersworld.com/kneestrength).
11. Why is it easier for me to run in the morning and so hard to rally at the end of the day—or vice versa?Your natural bird persona—lark or owl—is partly determined by genetics. Housed in the hypothalamus, the portion of the brain that also controls sex drive and appetite, your biological clock is difficult to alter. If your forebears coherently discussed the Middle East situation at 7 a.m., you're likely to feel sharp before the sun comes up, too. If they thought 9 p.m. was the perfect time for dinner, you probably are happy staying up late. "Natural morning people seem to hit their lowest body temperature earlier in the night than evening people do," says Chris Kline, an exercise physiology researcher at the University of South Carolina who specializes in sleep research. "Their body temperature is warmer when they wake up, so they're much more ready to go."
But even early birds aren't primed to perform at sunrise. "Typically, aerobic capacity is slightly lower in the morning because of a lower core temperature and lower levels of hormones that affect performance," says Matt Fitzgerald, co-author of The Runner's Body: How the Latest Science Can Help You Run Stronger, Longer, and Faster. In the late afternoon, the body is naturally the strongest and most flexible it'll be all day, plus your aerobic capacity is at its highest.
"Emotional moods and motivation have been shown to peak in the late afternoon," says Kline. "Nobody really knows why, but people are typically more willing to push themselves harder in the afternoon."Double your pleasure: Why running twice a day makes you fit and fast.
Running Rx: If you want to hit the track at 6 a.m.—and not hit anybody there over the head with a coffee cup—expose yourself to light, the easiest way to wake up your body, as soon as the alarm goes off. Also, realize that as you age, you naturally become more of a lark. Want to extend your staying power? Exercise either outside, if the sun is still out, or in a bright room two to four hours before bed. "It's tough to fight biological tendency," says Ronald Kramer, M.D., medical director of the Colorado Neurological Institute Sleep Disorders Center in Englewood, Colorado. "The important thing is to exercise, any time of day."
12. Why am I so sore after a marathon, when I've done 22-mile training runs?Did you do your training runs with crowds yelling at you and competitors around you unconsciously prompting you to run faster? Thought not. Whether you're a 2:30 or a 5:30 marathoner, your race-day pace tends to be at least a smidge—and possibly lots—faster than training days. That's the difference, says Dr. Bright, between being pleasantly and painfully sore. "You accumulate lactic acid in your muscles by pushing the pace, which brings on premature fatigue," says Dr. Bright. "Plus, the extra mileage—very few people do a 26-mile training run—causes more micro tears in your muscles, and it's likely your muscles haven't totally healed from your training. Race day, they get even more beat up." The combination nets marathonitis, an acute condition that demands stairs be taken backward and the size of a stride be cut in half.
Running Rx: A huge fan of ice baths, Dr. Bright recommends the anti-inflammatory plunge, post-race, for at least five to 10 minutes. Don't bother taking NSAIDs like ibuprofen. "The newer studies show they really don't do that much for inflammation," says Dr. Bright. "And they can potentially put your kidneys at risk."