2007_11_isla.jpgThe only time Paula Radcliffe seems to carry any body fat is when she's toting around her 9-month-old daughter around. Mothers, new and old alike, are still in awe over the British marathoner's ability to win the famed NYC marathon months after giving birth. The AP reports that she ran the 26.2 miles in 2 hours and 23 minutes (we've sat through football games this weekend that lasted longer) just 291 days after delivering little Isla. While running a marathon is an achievement for anyone, preggers or not, her accomplishment has stirred up debate on just how much exercise is safe for mommies-to-be.

Some docs feel that for ladies in tip-top shape to begin with, continuing their current level of activity into the early months of pregnancy should be fine as long as they cut back in the later stages and resume after giving birth. Those same docs ask that couch potatoes and weekend-warriors try not to engage in new strenuous work-out programs where they may overdo it as they feel the pregnancy pounds accumulating. (See more here.)

However, most physicians are not certain on how much exercise is unsafe, due to little research on the matter (pregnant women aren't necessarily the most willing test subjects). What is known is that women who've had cesarean sections usually take longer to recover and restart their usual workouts and should definitely wait until their incisions are healed before hitting the running trail. (Radcliffe happened to start running 12 days after giving birth.)

Strangely some of the physical changes involved with pregnancy, such as increased blood flow, may improve physical performance. But an enlarged belly can shift a woman's center of gravity and increased hormones swimming through the bloodstream may lead to looser and more easily injured ligaments and joints. Thus, the American College of Obstetrics and Gynecologists encourages more low impact exercises for the expectant, including swimming, walking, and yoga.