JAKARTA - Athletes declared the Asian Games' inaugural mixed 4x400m relay a fun - if chaotic - success on Tuesday, ahead of its planned introduction at the Tokyo 2020 Olympics.

Athletics bosses have introduced the concept - two men and two women on each team, running in whichever order they choose - as they seek ways to freshen up the sport and boost participation.

The eight teams in Jakarta tried out a range of combinations and strategies, as a bemused crowd struggled to figure out who was winning.

"First you feel like it's difficult because how can you run with girls?" said Abbas Abbas, of gold-winning Bahrain.

"But it's very nice especially when you trust your team. It's the first time I've raced with girls!"

The Asian Games race was the format's debut at a major multi-sports competition, ahead of scheduled appearances at next year's Doha world championships and the 2020 Tokyo Olympics.

IOC president Thomas Bach has promised the next Olympics will be "more youthful, more urban and include more women".

Mixed relay has been trialed at smaller events, including last year's Nitro Series in Melbourne.

Ultimately the countries that ran in a man-woman-woman-man order did best in Jakarta, with Bahrain and India pulling clear early on.

"We had two amazing girls. Very fast. Very strong. Like men. It was like we ran with four men!" said Abbas' teammate, Ali Khamis.

China's Yang Lei, whose team finished fourth, described the event as "chaos" after a gridlock emerged at the final baton handover, while Japan's Eri Utsunomiya - giggling at the confusion - said it was "fun ... just fun".