Mo Farah announced Friday he was targeting a return to the track to compete in the 10,000 metres at next year's Olympic Games.
The Briton has won double gold at each of the last two Olympics, taking the 5,000m and 10,000m crowns in London and Rio, but switched to the marathon in 2017.
Farah, 36, won the Chicago Marathon in 2018 but has decided to return to the track, admitting the marathon had been "a learning curve".
"The big news is I'm back on the track in the 10,000m in Tokyo next year," he said on his YouTube channel.
"I hope I haven't lost my speed but I'll train hard for it and see what I can do."
"(But) next year I've decided, Tokyo 2020, I'm gonna be back on the track. I'm really excited to be competing back on the track and give it a go in the 10,000m."