The Kenyan David Rudisha, who lit up the London Olympics with a bravura display of front running which brought him a gold medal and 800m world record, has pulled out of the world championships with a quad strain.

Rudisha, the world and Olympic champion and the only person to run under 1min 41sec for the 800m, said he was disappointed and saddened by the news, which was confirmed by an MRI scan on Monday revealing a grade‑one tear.

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“I was trying to engage more speed,” he said. “In the process I put my muscle under [more] intense stress than when doing normal mileage. I damaged my quad and this saddens and disappoints me a lot.”

The announcement of Rudisha’s withdrawal came as the first wave of Kenya’s team headed out to London for the championships which begin on Friday.

“We thought it was going to take a few days before recovery,” said Rudisha, who had been desperate to return to the stadium where he became a global star at London 2012. “But it’s taken longer than expected. When we went for an MRI scan they found that fluid was coming out of the muscle.”

The 28-year-old, who missed out on the 2013 championships with a serious knee injury before reclaiming his 800m crown two years ago in Beijing, insisted he would be back competing this year and said he wanted to challenge for the world title again in 2019.

“I have been advised that I should take it easy,” he said. “If I push it with that pain, it could damage me further – it is not the right thing to do or I would run the risk of missing the complete year. I have accepted my fate with a very heavy heart and would like to wish the team well. I will still come back stronger and even challenge for the title in the next world championships.”

David Rudisha MBS (@rudishadavid) Its sad and disappointing to announce my no show in the forthcoming #london2017 WC due to a quad muscle strain. pic.twitter.com/bdM0Zi4QCd

The Kenyan Emmanuel Korir, who has run 1min 43.10sec this season, and Botswana’s Nijel Amos – who took silver behind Rudisha at London 2012 – will be the favourites for gold in his absence.

Meanwhile Sebastian Coe, president of the International Association of Athletics Federations, has confirmed Russia will remain banned from international athletics for the foreseeable future. Coe, speaking following an IAAF council meeting in London, said: “Russia is moving in the right direction but the discussion we are having is about the speed of the process.”

Nineteen Russians will compete as neutral athletes at the world championships, after being approved by a special IAAF panel. Rune Andersen, head of the IAAF task force investigating Russia, admitted a number of conditions still needed to be met before the country was allowed back into the international fold.

“The main issue is that no meaningful testing is being conducted,” he said. “The Russian Anti-Doping Agency is still not World Anti-Doping Agency code-compliant. It has started testing but prior to being suspended they did 18,000-19,000 tests a year, now it is a few thousand. We are also working with the Russians on changing their culture. And they need to be able to suspend banned coaches – that still isn’t happening yet.”

Andersen’s comments came on the day when the IAAF’s Athletics Integrity Unit announced that 600 blood tests will be taken before the championships, with another 600 urine tests taken during the competition. That figure is 205 tests fewer than were carried out two years ago in Beijing but its chair, David Howman, insisted the organisation’s anti-doping programme was stronger than ever before.

“This is a very comprehensive intelligence-based anti-doping programme,” Howman said. “What is key to this programme is the significant work that has been done by the unit and its partners in the 10 months leading up to the championships to ensure that athletes competing in London have been part of a robust testing programme.”

The blood samples will be used to build biological passport profiles and detect prohibitive substances such as human growth hormone. The urine tests will be done on site in order to detect a wide range of substances including EPO and steroids.

The Athletics Integrity Unit also confirmed that over the past 10 months it had carried out 2,000 out-of-competition blood tests and about 3,000 urine tests.