Othman al-Busaidi gained his first international experience in 2011 when he finished fifth at the Asian Championships in Kobe with the Omani 4 x 400 meter relay in 3: 09.28 min. He then won the bronze medal behind the teams from Sudan and Saudi Arabia at the Arab Championships in al-Ain in 3: 08.82 minutes. In 2013 he took part in the Summer Universiade in Kazan for the first time , where he was disqualified in the 800-meter run in the first round and retired with the relay with 3: 19.50 minutes in the preliminary round. The following year he finished sixth with the relay at the Asian Games in Incheon in 3: 07.71 min and previously won the bronze medal behind the teams from Kazakhstan and at the Asian Indoor Championships in Hangzhou in a new national record time of 3: 13.49 min China. In 2015 he finished eighth in the 400-meter run at the Arab Championships in Manama in 47.98 s and then he reached fifth place in the relay at the Asian Championships in Wuhan in 3: 05.94 min. Then he got at the military world games in Mungyeon, South Korea over 400 meters to the semifinals, in which he was eliminated with 47.94 s and with the season he was seventh with 3: 10.24 min.
In 2017, at the Asian Championships in Bhubaneswar , he reached the semi-finals in the individual competition and was eliminated there with 47.74 s in the semi-finals, while he finished sixth in the relay in 3: 06.79 min. He was then at the Arab Championships in Radès in 47.64 s eighth over 400 meters and then retired at the Summer Universiade in Taipei with 47.20 s in the semifinals and was disqualified with the relay in the preliminary run. In 2019 he finished fifth in the individual competition at the Arab Championships in Cairo in 47.81 s and won the bronze medal behind the teams from Iraq and Algeria in 3: 11.82 min. At the end of October, he retired from the military world games in Wuhan with 47.10 seconds in the first round and finished seventh in the relay with 3: 10.52 minutes. In addition, this year he set a new indoor record in the 400-meter run in Tehran with 47.51 seconds .
Oman
