Wayde van Niekerk has changed coach as he steps up preparations for his 400 metres Olympic title defence in Tokyo.
The South African broke the men's 400m world record on his way to Olympic gold at Rio 2016.
Van Niekerk is aiming to beat his own time of 43.03secs to triumph again at Tokyo 2020.
To do so, Van Niekerk has parted ways with long-term coach "Tannie" Ans Botha and travelled to the United States to train under renowned sprint mentor Lance Brauman.
"I’ve spent most of my career under the guidance of 'Tannie' Ans Botha at my home base in Bloemfontein and I can’t express the gratitude I have for everything she has done to help me get to this point in my career," Van Niekerk said.
"As much as I have enjoyed my experience with Tannie Ans and her group, I am hoping to break my world record and to do that I need to ensure I am training alongside the world’s best sprinters.
"So I feel a temporary move to the United States will be in my best interests for the immediate future.
"I look forward to working with my new coach and training partners, and I hope to continue carrying the South African flag with pride at international level."
Van Niekerk's training partners at his new base in Florida will include America's 200m world champion Noah Lyles and women's 400m Olympic champion, Bahamian athlete Shaunae Miller-Uibo.
The 28-year-old has been recovering from an anterior cruciate ligament injury picked up in 2017, and suffered another setback earlier last year when he tested positive for COVID-19.
He returned to international competition in September, winning the men’s one-lap race at a European Tour meeting in Switzerland in 45.58.
Van Niekerk is a two-time world champion in the 400m, triumphing in 2015 and 2017, and also earned a world silver medal in the 200m at the latter competition in London.
He is set to compete at his second Olympic Games at Tokyo 2020, postponed to July 23 to August 8 2021 due to the coronavirus pandemic.
Van Niekerk acted as a flagbearer for South Africa at the Rio 2016 Opening Ceremony.