RAF flight sergeant Frans Bekker wanted to prove he ‘could still move’ when he tried to slide down the handrail at Holborn station.
But the 50-year-old lost control and wound up ploughing into three women, including Linda Soulsby.
Prosecuting lawyer John Swain told the jury at Westminster Magistrates Court: “Mr Bekker had hopped backwards onto the handrail of the escalator.
“He fell backwards into two women below him and a further woman, that being Ms Salisbury.
“They did not have a chance to brace themselves as they didn’t see it coming.”
Linda suffered a ’T12 transverse vertebral body fracture’ and was forced to wear a brace.
She has now been left with "an approximate 15 percent loss of vertebral body height”.
Christian Cormack, defending, said that Mr Bekker had been trying to show off to his table tennis teammates.
"He was mortified and has been since."
He will be sentenced on April 13.