NBC: Trans women retain athletic edge after a year of hormone therapy, study finds

A new study suggests transgender women maintain an athletic advantage over their cisgender peers even after a year on hormone therapy.

The results, published last month in the British Journal of Sports Medicine, could mean the current one-year waiting period for Olympic athletes who are transitioning is inadequate.

"For the Olympic level, the elite level, I'd say probably two years is more realistic than one year," said the study's lead author, Dr. Timothy Roberts, a pediatrician and the director of the adolescent medicine training program at Children's Mercy Hospital in Kansas City, Missouri. "At one year, the trans women on average still have an advantage over the cis women," he said, referring to cisgender, or nontransgender, women.

Roberts began investigating the athletic performance of transgender men and women while in the Air Force, working under co-author and physician Lt. Col. Joshua Smalley at a clinic coordinating care for airmen beginning or continuing their gender transition.

Active duty service members are required to take a physical readiness test every six to 12 months. Roberts, Smalley and another co-author, Dr. Dale Ahrendt, realized they had access to robust data on service members before, during and after they started hormone replacement treatment.

The three physicians conducted a retrospective review of medical records and fitness tests for 29 transgender men and 46 transgender women from 2013 to 2018. The Air Force's fitness assessment includes the number of pushups and situps performed in a minute, and the time required to run 1.5 miles.

They also had records on when the subjects started testosterone or estrogen, the type of hormone used and the number of days from when treatment began to when their hormone levels reached the normal adult range for a cisgender person.

For the first two years after starting hormones, the trans women in their review were able to do 10 percent more pushups and 6 percent more situps than their cisgender female counterparts. After two years, Roberts told NBC News, "they were fairly equivalent to the cisgender women."

Their running times declined as well, but two years on, trans women were still 12 percent faster on the 1.5 mile-run than their cisgender peers.

Unsurprisingly, testosterone affected the fitness scores of the transgender men they reviewed: Prior to starting hormones, they performed fewer pushups and had slower running times than the cisgender men in the control group. A year into treatment, though, those differences disappeared.

With situps, the trans men were comparable to the cisgender men before treatment and actually exceeded them after a year on testosterone.

The longest any participant was followed was two and a half years, according to Roberts.

He said he's not suggesting being in the military is the same as being an elite athlete, but, he added, "it's a comparable situation, where you have someone doing whatever they can to maintain or improve their abilities."

Joanna Harper, a medical physicist in Portland, Oregon, has conducted research into the effect of testosterone blockers on transgender women runners like herself.

In 2015, she published the first study of transgender women and athletic performance and found that trans women ran at least 10 percent slower after beginning hormones. And, relatively speaking, they did no better against cisgender female runners than they had previously done against cisgender men.

Harper said Roberts' methodology is solid, but she sees some limitations in the study. In an assessment shared with NBC News, she questioned the lack of data on participants' individual training habits. She also noted there was no coordination between when subjects started hormones and when they took their annual fitness test.

"The tests were placed into three bins," Harper said. "One bin of tests that took place in the first year after the start of hormone therapy, one bin of tests that took place between one to two years of hormone therapy, and a third bin that took place between two and two and a half years after the initiation of hormone therapy."

Lumping the data together could blur out changes that occurred within a 12-month period "and might distort the results notably," she theorized.

The fact that the trans women were still faster after two years could be due to differences in training intensity, she speculated. But the pushup and situp tests involve muscular strength, technique, muscular endurance and cardiovascular endurance, and "are probably good proxies for success in many team sports."

As the transgender community has become more visible, their place in athletic competitions has come under increased scrutiny.

In October, the World Rugby League became the first international sporting body to ban transgender women from playing in the women's division, citing "player welfare risks." Two months later, a group of 200 elite female athletes - including Billie Jean King, Megan Rapinoe and Candace Parker - signed a friend-of-the-court brief supporting the rights of trans women and girls to participate in female sports.

The brief was filed with the 9th U.S. Circuit Court of Appeals in response to Idaho's Fair... (Read more)

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