Active Voice: Sex Differences in the Marathon – Nature or Nurture? By Sandra Hunter, Ph.D., FACSM Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM. Sandra Hunter, Ph.D., FACSM, is Associate Professor in the Exercise Science Program, Department of Physical Therapy at Marquette University in Milwaukee. Her research focus includes understanding the mechanisms for sex and age differences in motor control and neuromuscular fatigue and the added impact of psychological stress. In the April 2011 issue of Medicine & Science in Sports & Exercise® (MSSE), Hunter and co-authors published a related research paper entitled “Is There a Sex Difference in the Age of Elite Marathon Runners?” In 1992, a controversial article in Nature projected, based on improvements in running times from previous decades, that women would outrun men in the marathon by 1998. This did not occur because the physiological differences between elite men and women runners still exist. Men, on average, have less body fat, larger hearts and greater hemoglobin concentration than women, facilitating larger maximal oxygen consumption and faster marathon times (for more, see article by Michael Joyner). In a recent article in MSSE, we highlighted the sex differences in the age and performance of elite marathon runners. The findings offer a glimpse into sex differences in physiology and other sociological factors that affect performance. In our study, we compared the ages and running times of the first five men and women finishers from each of the seven premiere marathons that constitute the World Marathon Majors Series. Men were 10-12 percent faster than women. This sex difference has remained constant over the last few decades and primarily reflects differences in physiology between men and women. Interestingly, the age at which men and women were winning these marathons was relatively similar, at ~29 years, with a 20-year age range for both sexes. Hence, the 17-year age gap between the male (21 years) and female (38 years) gold medalists in the 2008 Beijing Olympics marathon is likely an anomaly rather than the norm. One of the most intriguing findings was that the sex difference in running velocity progressively increased between first and fifth place. This widening in the sex difference could result from a lack of depth in women runners compared with men. It may also reflect a larger issue of participation in physical activity among men and women within society. That is, historically men have had more opportunities than women to participate in sports. Women, for example, were first permitted to participate in the marathon in the late 70s. The first women’s Olympic marathon in 1984 (Los Angeles) is etched in the minds of many. Today, participation rates in running events remain lower for women than for men. As we noted in our recent article, the ratio of women to men runners in marathon events has progressively increased over the last 30 years, but there is still a larger pool of male competitors. Lower participation rates of women appear to be accompanied by a larger sex difference in performance than can be explained physiologically and likely represents sociological factors that still linger. The sex bias in participation in physical activity is also evident in the general population. Men are widely reported to be more active than women. Although more opportunities are available for women now, there are still sociological forces at work that translate into less active women. These issues deserve attention. Interestingly, I watch my daughter participating in the rigors of gymnastics with a room full of other girls. In this example, the tables are turned; girls outnumber boys five-to-one. It is clear the sex bias in participation can be sport-specific. Regardless, it remains that for whatever sociological reason(s), women do not participate in physical activity or running events at the same rate as men. It may even explain the increased sex difference in performance among higher-level athletes.