In 1987, Michael Jackson seemingly defied gravity in the video of his song Smooth Criminal, when he leant 45° forward, his spine straight, with only his feet preventing him from falling over. Three decades later, three neurosurgeons from the Postgraduate Institute of Medical Education and Research (PGIMER) in Chandigarh have deciphered the biomechanics that enabled Jackson to perform a move that not many other dancers could be expected to match.
With a mix of two factors, the doctors reported. One was a specially designed shoe, patented by Jackson’s team, that balance him in that position by hitching him to the stage. Two, the sheer strength in Jackson’s tendons. Otherwise, the doctors believe, even the strongest and best-trained dancers can go up to a maximum of only 25° to 30° while bending forward.
When a person stands with his or her back straight, the centre of gravity is in front of the second sacral vertebra (lower part of the spine). When the person bends forward with the back straight, the hip joints act as a fulcrum, on which the body moves forward. The muscles of the back support the spine and act as a cable while the body makes its movements. This helps in maintaining balance without the body falling forward.
“However, when the fulcrum for forwarding bending is shifted to the ankle joints, the erector spinae (muscles supporting the back and vertebral column) lose their ability to maintain the centre of gravity, and strain is shifted to the Achilles tendon,” the doctors said in the study.
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In Jackson’s case, the authors said, his special shoes “had a slot in the heel”. “The triangular slot could engage a hitch member (a metallic peg, which emerged from the stage floor at just the right time), allowing the dancer to obtain the right amount of extra support to be able to lean forward beyond physiological limits,” the study says.
Yet, even with the special footwear, the move would be possible only with “athletic core strength from strengthened spinal muscles and lower-limb antigravity muscles”. Dr Tripathi told The Indian Express from the UK that they have concluded that the secret lies “in the inventiveness and core muscle strength”.
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