Khan told the Afrikaans daily Beeld that he had asked the Knights fitness expert Adrian le Roux to help him with his pre-season conditioning during the IPL in May.
Le Roux assisted the Proteas and the Indian national team and has become a close friend of Khan.
Khan has been hard at work in Bloemfontein, the home base of the Knights, for several days now, participating in training sessions ahead of a training camp in Port Elizabeth next week with the Warriors.
"I earlier started working on my fitness for the coming season in France. I have to return on September 27 to play for India A against the West Indies," Khan told the daily.
Khan last played for India against England in Kolkata in December 2012. The bowler was hopeful of convincing the Indians selectors that there was still a lot of cricket left in him despite being 35.
With 88 Tests behind him, Khan needs just five more wickets to reach the milestone of 300. Playing against South Africa, Khan twice took four wickets in an over
Image: Zaheer Khan
Photograph: Hamish Blair/Getty Images
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