Sun Yang of China reacts after the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Tao Xiyi)

Sun Yang of China reacts after the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Tao Xiyi)

Sun Yang of China reacts after the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Tao Xiyi)

Sun Yang of China reacts after the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Tao Xiyi)

Sun Yang (C) of China, Mack Horton (L) of Australia and Gabriele Detti of Italy pose during the medal ceremony for the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Bai Xuefei)

Sun Yang (C) of China, Mack Horton (L) of Australia and Gabriele Detti of Italy pose during the medal ceremony for the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Bai Xuefei)

Sun Yang of China reacts during the medal ceremony for the men's 400m freestyle final at the Gwangju 2019 FINA World Championships in Gwangju, South Korea, July 21, 2019. (Xinhua/Bai Xuefei)