Paula Radcliffe, the British runner who holds the world record in the women’s marathon, ran throughout her pregnancy last year. She even ran the day before she gave birth, to a healthy baby who was named Isla, on Jan 17. And 12 days after Isla’s birth, she started running again.

Last week she won the New York City Marathon, her first marathon in two years. Her experience is unprecedented, says James Pivarnik, director of the Human Energy Research Laboratory at Michigan State University and one of the few scientists who have studied athletes during and after pregnancy.

“As far as I know, no one has ever done what she’s done,” Pivarnik said.

For the first five months she ran twice a day, 75 minutes in the morning and 30 to 45 minutes in the evening.

Then she cut back, running an hour in the morning and riding a stationary bike at night. She even did training regimens like hill repeats — repeatedly running up hills to build strength and endurance.

“People were looking at her as if she was crazy,” says Gary Lough, her husband and manager.

Radcliffe, 32, set the world record at the 2003 London Marathon with a time of 2 hours, 15 minutes, 25 seconds, a pace of barely 5 minutes per mile over the 26.2-mile course.

No rigorous studies have explored whether pregnancy improved or hindered the performances of elite athletes, before or after giving birth. Researchers and pregnant women are not inclined to conduct or participate in studies in which the women would exercise at various intensity levels and possibly endanger the babies.

All that is left are case histories and myths. For example, Ingrid Kristiansen won the Houston Marathon in 1983, five months after she gave birth to her first child. That led to hypotheses that pregnancy helps elite runners because of physiologic changes.

Blood volume increases by 60 per cent during pregnancy, which may suggest a woman would have so much extra blood after her baby is born that it would be the equivalent of blood doping — getting extra blood to carry oxygen to muscles. But Pivarnik noted that blood volume returns to normal within four to eight weeks after a woman gives birth.

Radcliffe said that when she became pregnant, she did not want to stop running. But Lough said Radcliffe’s doctor was concerned.

Lough said that when Radcliffe is racing, her heart rate often exceeds 180 for more than two hours. Keeping it below 160, Radcliffe said, meant running was much easier.

Twelve days after Isla was born, Radcliffe tried running again. “I felt a bit wobbly,” she said, “but I was glad to have my body back.”

The injuries she sustained after she resumed running deprived her of more than two months of training, but in the end, Radcliffe says, she was able to train enough to properly prepare for the New York marathon.

Radcliffe says these days she thinks she can run better than ever. Her endurance is better than before she was pregnant, she says, and her recovery from hard workouts has been faster.

NYT