In addition to training, get educated about healthy eating, says Lisa Dorfman, director of sports nutrition and performance at the University of Miami.
"Women coming out of their college years have erratic eating habits," she says. "They grab ice cream after being at the club, but ignore fruits, veggies and whole grains. Good eating habits support running and prevent injuries."
In Your 30s
This decade is a study in contrasts. At 30, a woman is often at her physical peak, but by 40, her aerobic capacity and muscle mass declines. Ball State University researchers found athletes who train vigorously often don't experience significant drop-offs in performance until they reach their middle 40s or early 50s. By logging miles, pushing the pace and adding cross-training, a woman in her 30s can be competitive, especially at longer distances.
"Women who had 5k PRs in their 20s," Hinton says, "can now look to 10k and longer races to perform their best." Why? Thank the "10-year rule," says Dr. David Brock, assistant professor of exercise and movement science at the University of Vermont.
"It's not that women in their 30s necessarily do better at longer distances," he says. "You reach your peak potential about 10 years after you start running, no matter what decade you start. If everything else is relatively equal, a 30-year-old woman who has been training for 10 years will do better in a race than a 22-year-old training for two years."
By the late 30s, it's harder to recover from a long run or race. That's because muscles store glycogen, the fuel your body uses during exercise, so when you lose muscle mass with age, you also lose some of your glycogen reserves. This means it takes longer to replenish them after a hard effort.
The best way to refuel: Eat carbohydrates such as fruits, vegetables, yogurt, whole grains or beans.
"Women this age lose track of what they're eating because they're so busy," says Dorfman. "It's important to eat healthy on a regular schedule."
Don't neglect strength training even if you're busy juggling a career, family and workouts.
"Good strength-building moves include lunges, squats, crunches, leg lifts and biceps curls," says Hinton. "If time is tight, be creative: Add 30 minutes of strength training two to three times a week while you're watching TV."
In Your 40s
By the time you're a masters runner (40 and older), your aerobic capacity, muscle mass and ability to recover decline, but all of these variables can be mitigated. The bottom line: Keep running and you'll get solid race results.
Your resting heart rate doesn't change as you age, but your heart doesn't pump as fast as it once did. "Get out of your comfort zone to improve your aerobic capacity," says Dr. Stephen Pribut, clinical assistant professor of surgery at George Washington University Medical Center.