Joanna Harper in Lausanne, Switzerland this week. (SEBASTIENAGNETTI/For The Washington Post)

Joanna Harper is a medical physicist at Providence Portland Medical Center in Oregon.

I was 150 meters from the finish of the eight-kilometer national Masters Championships in Brea, Calif., when I switched on what passes for a kick in a 58-year-old woman like me. Up ahead I saw Suzanne Cordes, a 55-year-old Bay Area runner and personal trainer who is ranked internationally in World Masters Athletics. I’d never beaten her in a race.

With mere meters left, I caught up to Suzanne. And then I edged past her into the finish chute. I clocked in at 36:14, she at 36:18. I was still bent over from the exertion of the sprint when she walked by and affectionately squeezed my hand. It was a small gesture but a meaningful one. That moment, in February, stood out because it was so different from the reception I often receive as a transgender athlete.

I started hormone therapy in the summer of 2004, and I’ve raced as a woman since the spring of 2005. Although the International Association of Athletics Federations (IAAF), the world track and field association, allows it, and some of my fellow runners have been accepting, other runners are notably chilly toward me. Or they tell me that it’s fine for me to race — as long as I don’t beat them.

Such comments leave me feeling in­cred­ibly defensive. How slow would I need to be for them to be happy? I could point out that the five women in my age group who ran faster than me at the masters in February have the advantage of living in sunny California, while I have to train through the rain of a Portland winter. Or I could acknowledge that Cordes was at a disadvantage, having just come back from an injury. But for some people, no variable matters as much as gender assigned at birth. They can’t get past the idea that I’m a man trying to profit in a woman’s sport.

The pushback I’ve experienced has been mild compared with that faced by Renée Richards, probably the best-known transgender athlete, who had to sue the U.S. Tennis Association in the 1970s to play as a woman at the U.S. Open. Or, to take a more recent example, consider the vitriol launched at mixed martial arts fighter Fallon Fox since she came out as transgender in 2013. She was called a “lying, sick, sociopathic, disgusting freak” by fellow MMA fighter Matt Mitrione. One of Fox’s opponents played Aerosmith’s “Dude Looks Like a Lady” as her entrance music. Another complained that Fox should be barred from competition because of her “advantage.” (That fighter, Ashlee Evans-Smith, was suspended in February after testing positive for an illegal diuretic.)

All successful athletes have advantages over less-successful athletes — just ask anyone who has had to guard LeBron James. The question is whether trans women can compete equitably against other women. And in many sports, the evidence supports an emphatic yes.

One indication of fairness is that fears of trans women dominating in women’s sports have never been realized. Richards was knocked out in the first round at the U.S. Open. Golfer Mianne Bagger may have seemed like a giant-killer when she was winning Australian national amateur titles, but once she began to play against the pros in the Ladies European Tour, she was quickly relegated to also-ran status. Similarly, while Fox’s 5-1 professional fight record may seem gaudy, she toils in MMA’s minor leagues and, as so often happens when fighters are elevated, she would be promptly dispatched if she competed in the top-tier Ultimate Fighting Championship.

Science provides a clear explanation for why, in many sports, trans women don’t maintain any athletic advantage. Hormone therapy for trans women typically involves a testosterone-blocking drug plus an estrogen supplement. As their testosterone levels approach female norms, trans women see a decrease in muscle mass, bone density and the proportion of oxygen-carrying red cells in their blood. The estrogen, meanwhile, boosts fat storage, especially around the hips. Together, these changes lead to a loss of speed, strength and endurance — all key components of athleticism.

I understood that this would happen to me, too. But I was surprised how fast it happened. Within three weeks of starting hormone therapy in August 2004, I was markedly slower. I didn’t feel any different while I was running. But I could no longer match my previous times. By 2005, when I was racing in the women’s category, the difference was astounding. I finished one 10K in 42:01 — almost a full five minutes slower than I’d run the same course two years earlier as a man.

Interestingly, when I looked up my times in USA Track & Field’s age-grading tables — used to compare runners of all ages and both sexes — I found that I was just as competitive as a 48-year-old woman as I had been as a 46-year-old man.

I was curious whether my experience was typical. There had never been any studies of transgender athletes, only of transgender women generally. So over the next seven years, I collected almost 200 race times from eight distance runners who were transgender women (including myself as runner No. 6).

My research, published last month in the Journal of Sporting Cultures and Identities, found that collectively, the eight subjects got much slower after their gender transitions and put up nearly identical age-graded scores as men and as women, meaning they were equally — but no more — competitive in their new gender category. (The outlier was a runner who had raced recreationally as a 19-year-old male and became serious about the sport — doubling her training load and shedding 22 pounds — years later as a female.)

To be clear: This study speaks only to distance running. Trans women who are sprinters may maintain something of an advantage over other female runners in that they tend to carry more muscle mass, potentially allowing for increased speed over short distances. (Whereas extra muscle mass is a disadvantage in distance running.) And since gender transition doesn’t affect height, it would make sense that transgender women would have advantages over other women in sports such as basketball, where size is so important, and disadvantages in sports such as gymnastics, where greater size is an impediment.

Still, my results help support the rules of the IAAF, which allows anyone who is legally and hormonally female to compete in women’s events. They also offer an endorsement of NCAA rules, in place since 2011, that allow trans women to compete as female athletes a year after beginning testosterone suppression. And they suggest that the International Olympic Committee may want to modify its rules requiring that trans women undergo surgery and two subsequent years of hormone treatment before they can compete. As it stands, a transgender woman may be eligible to compete against other women in the IAAF-sponsored world championships but not in the 2016 Olympics. (Trans men — who don’t tend to prompt the same anxieties about dominating their sports — only have to file a therapeutic-use exemption with the IOC or the IAAF to cover their testosterone shots.)

I hope the mounting evidence, coupled with exposure to trans women athletes, will go some way toward changing hearts and minds. The rules established by different leagues are unnecessarily inconsistent, and prejudice persists at all levels of sport — from elite leagues down to high school teams.

All athletes who devote their time to getting better, stronger, faster should understand that it’s not easy to voluntarily give up strength and speed, to accept that you’ll never again match your personal best. But that’s one sacrifice transgender women make in order to live as the people they feel they are. And a hand squeeze of acknowledgment can go a long way.

jmharps57@gmail.com

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