Grace Padilla, 36, of Los Angeles, took eight years off to finish college and have two kids. "When I returned to running in 2003, I was so hungry for it," she says. "The first time back on the track was painful, but the body remembers how to run fast, and the mind remembers how to deal with the pain."
Natural strength peaks in this decade. "Over time, runners' bodies learn how to build and efficiently recruit the key running muscles," says Tim Noakes, M.D., a sports-medicine specialist and author of Lore of Running. That means that in distances of 10K and longer, you can clock consistent times until you're 35, regardless of how you train.
"After that, you can't rely on your age to predict your speed," says Hirofumi Tanaka, Ph.D., associate professor of kinesiology and health education at the University of Texas at Austin. "The amount and intensity of your training becomes very important." If you're a marathoner, you've found your tribe at the races: The average age of U.S. marathoners is 38. No doubt, a set training schedule adds structure to your otherwise chaotic life. But there's another good reason 30-somethings gather to run
That roll that's hanging over your running shorts? Sorry, but you can't blame it on your slowing metabolism. More likely, it's too many trips to the drive-thru and too few around the track. Yes, metabolism slows a bit naturally—you need, on average, about 120 daily calories less at age 35 than you did at 25. But what really causes it to slam on the brakes is less lean body mass (you're not strength training) and less activity (you've cut your mileage). Adding a tempo run and some resistance training on top of your regular runs would be ideal. You could also incrementally up your mileage to maintain your weight. Researchers from the University of California at Berkeley followed 5,000 male runners under the age of 50. The average 6' tall runner gained 3.3 pounds per decade. To offset the gain, the researchers recommend running 1.4 more miles weekly per year. If increasing your mileage isn't an option (or appealing), cross-train more or eat less.
Sure, you're changing a diaper with one hand and firing off e-mails with the other, but unless you also want to add nursing an injury to your to-do list, don't neglect strength training. Not only does it prevent sprains and strains by building up connective tissues around your joints, but resistance training also increases your running economy (by lowering the amount of oxygen you need to attain a certain speed). Don't worry — you don't need to join a gym. Just do two sets of 12 lunges, squats, calf raises, hamstring curls (with a stability ball), core work (plank position and sit-ups on a stability ball) and push-ups two or three times a week. On your runs, make the most of your limited time by periodically pushing the pace—do some pickups or a mile or two of tempo work.
To prevent the need to upsize your shorts, reevaluate your calorie needs. Find your ideal number by multiplying your weight by 10, add the number of calories you burn running (a 150-pound person burns, hourly, about 600 calories for a 10-minute mile pace, 670 for a nine-minute mile, 750 for an eight-minute mile), then add 10 percent of that figure to get your grand total for the day. On days when you don't run, subtract 300 to 500 calories from your daily total (unless you are burning an equivalent amount of calories cross-training), says nutritionist Lisa Dorfman. She also warns not to skip meals: "Doing so slows your metabolism, which makes it more difficult to manage your weight."
Grace Padilla, 36, Los Angeles
Running since: age 12
Résumé: competed in 1996 Olympic Trials exhibition event; trains with The Janes, an elite racing club; ran a 17:16 5K at 35 What I've learned "Running changed my life. It gave me a reason to go to college, developed who I am as a person, and continues to make me strong. I don't have the time to make it a first priority — I'm a first-grade teacher and single mom. But running gives my life balance and my body energy. I want to be a good role model, to girls in particular. I tell them, 'Boys aren't necessarily faster than girls. I can beat a lot of men.'"
What works for me: "No matter how drained I feel after work, I know a run will make me feel better. My mind becomes happy, and my body feels great."