Michael Jackson's legendary dance moves revolutionized the music industry, and even nine years after his death, doctors are still trying to figure out how the King of Pop was able to do what he did.Neurosurgeons at the Postgraduate Institute of Medical Education and Research in Chandigarh, India, published a study in the Journal of Neurosurgery that took a look at the iconic lean that Jackson debuted in his 1988 "Smooth Criminal" music video.Jackson accomplished the gravity-defying move by leaning his body forward to a perfect 45 degree angle, while keeping it completely straight. "Most trained dancers with strong core strength will reach a maximum of 25 to 30 degrees of forward bending while performing this action," neurosurgeon Manjul Tripath said. "MJ pulled off a gravity-defying 45 degree move that seems unearthly to any witness."The Secrets of a Smooth CriminalSo how exactly was the King of Pop able to pull it off? Researchers discovered that the secret is in his strong core and fancy shoes.According to the BBC, Tripath explained that most people who attempt the lean find most of the strain is in the Achilles tendon of each ankle, rather than the erector spinae muscles of the back. However, researchers found that a strong, athletic core from strengthened spinal and lower-limb muscles help the dancer successfully do this move."The chances of injury to the ankle are significant," Tripath warned. "You need strong core muscles and good support around the ankle. It's not a simple trick."Jackson also got an upper hand on his fellow dancers by patenting and designing a one-of-a-kind shoe that would assist him in pulling off the move. According to Complex, the shoes had a specially-designed heel peg that would protrude and connect to the stage, allowing Jackson to shift his balance and perform the lean. The patent was first created in 1993, but expired in 2005. The revolutionary shoes were reportedly auctioned off for $600,000 in 2009. MJ's talent, however, is priceless.