How Pregnancy Affects Your Marathon Time

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A few years ago, Nike-sponsored runners Alysia Montaño and Kara Goucher publicly revealed the extent to which their salaries were reduced when they became pregnant. Allyson Felix followed up with the story of how Nike offered her a contract with a 70 percent reduction in salary after she became pregnant. “Getting pregnant,” former Nike runner Phoebe Wright said, “is the kiss of death for a female athlete.”

There are some basic questions about right and wrong here. But there are also some physiological questions. Is it correct to assume that once a woman becomes pregnant, her best athletic days are behind her? After all, some researchers consider it an arduous feat of endurance to carry a baby to term that runs counter to the ultimate human boundaries. Or, conversely, could it be that female athletes actually have a postpartum benefit? This is what other experts suggest, pointing to lasting changes in cardiovascular abilities such as the amount of blood the heart can pump and potential increases in pain tolerance.

What we need is data, and that’s what a new study in the European Journal of Sport Science supplies. A research team led by Nicolas Forstmann of the Institute for Research in Biomedicine and Epidemiology of Sport and the National Institute of Sport Science and Performance, in France, analyzes the career trajectories of the fastest female marathon runners in history — and concludes that birth doesn t really make a difference anyway.

The analysis included the 150 fastest female marathon runners of all time, based on the lists maintained by World Athletics. By searching official records, news reports and personal websites, they identified 37 of these runners who gave birth to children during their elite athletics careers, meaning they had at least one elite level achievement in the World Athletics Database at distances between 1,500 . meters and the marathon both before and after childbirth. Of these 37 athletes, 23 had one child during their careers, at an average age of 28.3; the other 14 had two children, at average ages of 24.7 and 32.6.

Overall, 26 of the 37 runners ran their fastest times (average 2:21) after their first child. If you put it in more detail, in the one-child group, eight runners ran their best time before children and 15 their best times thereafter. In the two-child group, three ran their best time before children, five between children and six after the second child. On the face of it, it looks pretty good.

The big confusion here is age. The athletes were absent from the World Athletics Database around birth for an average of 23 months, with a range from 9 months (wow!) To 94 months (also wow!). Time is waiting for no woman, so it’s hard to know if a post-pregnancy drop in performance because you’re a year or two older – or vice versa, for a relatively young mother, or a post-pregnancy increase in performance simply as a result of additional training and experience.

To take into account the effects of age, Forstmann and his colleagues use mathematical modeling to outline the typical career trajectory for female marathon runners. For the 37 women in the study, that ratio looks like the graph below, with a gradual increase in performance to a peak age of 31.7, followed by a gradual decrease in performance:

(Photo: European Journal of Sport Science)

The timing of pregnancy had no observable effect on this curve. Women who had their first child before the age of 31.7 tended to get better after pregnancy; those who gave birth after that age tended to get worse. Having children apparently has not fundamentally changed anyone’s trajectory.

However, there is a huge gap in the dataset. What about hypothetical runners whose careers have been derailed by pregnancy? Maybe they ran 2:21 pre-kid, and then never managed to return to world class level and so they disappeared completely from the World Athletics Database? They will not be included in the study at all as they have not returned to top level competition so we have no way of knowing if this is happening to anyone. It’s a totally made-up scenario, but it’s worth acknowledging that pregnancy and childbirth pose real challenges for elite-level training. Loose ligaments can alter running mechanics, torn abdominal muscles compromise stability, the metabolic demands of breastfeeding can leave you calorie-depleted and vulnerable to stress fractures. All of these issues are common among athletes who rush back to postpartum after full training. Patience – the kind you can only have when your employer does not link your next salary to your immediate return to competition – is key.

Despite that blind spot, I think the new data is reassuring. Women who are able to successfully return to training and competition after giving birth seem to be going pretty much where they left off, taking into account the passage of time. Since Montaño, Goucher and Felix spoke, Nike and other companies have made public commitments to protect athlete compensation during and after pregnancy. I suspect athletes are still nervous about telling their sponsors that they want a family, but hopefully this data will provide them with useful ammunition for the conversation.

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