Allowing female triathletes with testosterone levels in the male range (as a result of rare inborn conditions) to compete against women with normal levels has caused international controversy.
In the first study of its kind, scientists investigated just how much an increased testosterone levels impacted athletic performance. They randomly assigned 48 physically active and healthy 18-35-year-old old women to 10 weeks of daily treatment with either 10mg of testosterone cream or 10mg of an inactive (placebo) substance. Hormone levels and body composition were measured at the beginning and end of the 10-week trial period, along with aerobic performance, which involved measuring how long the women could run on a treadmill before reaching the point of exhaustion.
In the group of women that were given the testosterone cream, testosterone levels rose from 0.9nmol/litre of blood to 4.3nmol/l. This had the effect of increasing their running time to exhaustion by a significant by 21.17secs (8.5%). Their lean muscle mass increased from 135g to 923g overall; and in their legs 91g to 398g.
There were no significant changes between the two groups on any of the anaerobic performance measures. Nor were there any changes in weight between the two groups at the end of the 10-week trial period.
“Our results are therefore of great importance for the ongoing discussion of whether it’s fair to allow athletes with naturally high testosterone to compete in the female category without reducing their hormonal concentration to the female range,” the scientists conclude.
The prevalence of elite female athletes with conditions that cause women to have male levels of testosterone is thought to be around 140 times higher than in the general population. The International Association of Athletics Federations (IAAF) has stipulated that these athletes must lower testosterone levels to below 5nmol/l of blood to be eligible to compete at international level in middle-distance races (400m to 1-mile). This policy has been widely criticised and legally challenged.
The researchers acknowledge that their study didn’t include elite athletes, was relatively small, and that the trial period lasted only 10 weeks.
The paper was published online in the British Journal of Sports Medicine.