Some advice from Simon Cowell: "If you buy an electric trail bike, read the manual before you ride it for the first time." The America's Got Talent creator tweeted the advice Sunday, the day after he broke part of his back testing the bike in the courtyard of his Malibu home. The 60-year-old was in surgery for five hours on Saturday and had a metal rod put in his back, the BBC reports. Cowell also tweeted a "massive thank you" to all the nurses and doctors who treated him at a Los Angeles facility, describing them as "some of the nicest people" he has ever met. Variety reports that Cowell will miss the first two live shows of America's Got Talent, which air this Tuesday and Wednesday. (More Simon Cowell stories.)