Explainer-How will swimming's new transgender rules work?

Swimming's world governing body FINA has voted to restrict the participation of transgender athletes in elite women's competitions and create a working group to establish an "open" category for them in some events as part of its new policy.

Here is an explanation of what the policy is and FINA's reasoning behind the change:

WHAT IS THE REASON FOR THE NEW POLICY?

FINA officials said the aim of the policy was to ensure fair competition in women's races.

FINA cited scientific evidence that males who transition to being women (transgender women) retain physical advantages despite undergoing hormone therapy and testosterone reduction as part of their treatment.

"By 14 years or older, the difference between boys and girls is substantial. That's due to the advantages experienced due to the physiological adaptations in testosterone and the possession of the Y chromosome," said Dr Sandra Hunter, an exercise physiologist who was part of FINA's panel looking into the issue.

"Some of these physical advantages are structural in origin such as height, limb length, heart size, lung size and they will be retained, even with the suppression or reduction of testosterone that occurs in the transition from male to female."

WHAT IS THE BIG CHANGE?

The new eligibility policy for FINA competitions states that male-to-female transgender swimmers (transgender women) are eligible to compete in women's competitions only if "they can establish to FINA's comfortable satisfaction that they have not experienced any part of male puberty beyond Tanner Stage 2 (of puberty) or before age 12, whichever is later".

WHAT IS 'TANNER STAGE 2'?

Typically boys will begin puberty at ages 11-12 and complete the process by 16-17. Tanner Stage Two is the second of five stages