July 20, 2011
What makes a female athlete different from a male athlete? Watching Abby Wambach leap above defenders in a World Cup soccer game to head the ball decisively into the net, or seeing her teammate Megan Rapinoe streak a pass down the pitch, the answer might seem to be: not much. As a group, female athletes, like their male counterparts, display coordination, strength, grace, speed, stamina and a bracing competitiveness.
But there is a signal difference between adult men and women, on the field and off. Women menstruate. And menstruation, with its accompanying fluctuating levels of the female sex hormone estrogen, can have a considerable effect on how a woman’s body responds to the demands of exercise and competition, as a range of provocative new science makes clear.
Consider the results of a series of experiments published last month involving female rowers in Europe. Some of the women were competitive athletes, others hobbyists. Some were using oral contraceptives, which lower production of the body’s own estrogen while maintaining consistent levels of a synthetic variety; others were not. All of the women came into the lab multiple times throughout the month, including on days when their estrogen levels were at their peak and ebb, to complete a fitness test on a computerized rowing machine. Each time, their heart rates, oxygen consumption, power output, blood lactate levels and other measures of endurance, strength and general fitness were measured.
Those measurements, as it turned out, never varied, no matter where a woman was in her menstrual cycle. She could row just as long and powerfully whether her estrogen levels were high, low or in between; whether she used contraceptives; and whether she was an experienced, competitive athlete or a rowing duffer.
These findings are important, because many people, including coaches and athletes, have long contended that women’s endurance and overall performance may flag at certain times during the month — although there is disagreement about when those times are. And many female athletes have been told, or have chosen, to start or discontinue using birth control pills to manipulate their hormone levels.