Martyn Lee, 46, went berserk when Caroline Livesey undertook him and then swerved in front of his van to avoid a dog, which had run into the road.
The plumber had to overtake Iron Man competitor Ms Livesey by driving into the opposite carriageway, the court heard.
He then drove ahead, pulled over his silver Ford Transit, jumped out and knocked the 38-year-old down. Ms Livesey fractured her spine and suffered cuts and bruises to her lower back and head during the attack near Harrogate at about 1pm on May 11th this year.
The court heard that since the crash the keen sportswoman has been left in fear every time she rides her bike.
The driver went berserk after being undertaken by a female triathlete
Ms Livesey, pictured, fractured her spine and suffered cuts and bruises to her lower back and head during the attack
Prosecutor Shawn Morales told York crown court: "The defendant had been driving along when the complainant, who was at the left side of the road, had moved over to the right to avoid hitting a dog.
"As she pulled across the road, the defendant had to then drive into the middle of both carriageways to narrowly miss Mrs Livesey.
"The complainant said the defendant then drove past her shouting something about 'undertaking' referring to a previous incident of driving down the inside lane.
"Further down the road he had stopped and, as the complainant went past, he rugby tackled her from the bike and she hit the back of her head on the road surface. After the incident, he told her, 'To be honest, I thought you were a bloke'.
The court heard that since the crash the keen sportswoman has been left in fear every time she rides her bike
After he knocked the victim off her bike he told her: "I thought you were a bloke"
Prior to the crash Ms Livesey was described as 'semi-pro' and at the point of gaining a qualification for a triathlete spot at the 2017 world championships.
A month earlier she had secured a top 10 finish in a gruelling North America iron man challenge, which included a 3.8 mile swim, 117 mile bike ride and a marathon.
In a victim impact statement, Mrs Livesey, of Harrogate, North Yorkshire, said: "I no longer feel safe when on my bike and have ridden my bike in fear for months.
"I have lost earnings - I lost out in prize money for qualification to these events and I am still in part-time employment."
Mrs Livesey also had her £340 iPhone and £209 helmet camera broken.
The court heard Lee had been targeted by a social media hate campaign, which lost him plumbing business.
The plumber was angry when he had to overtake Iron Man competitor Ms Livesey by driving into the opposite carriageway, York Crown Court heard
Defending Lee, Ayisha Smart, said: "He says that he merely pulled over further up the road to try and speak to the victim, but the build up of stress he was under at work let his anger get the better of him.
"This is the defendant's first blemish on a record of 46 years.
"He has given a guilty plea at the first opportunity, the same plea given to police officers at the scene of the incident. "
Lee, from Lofthouse, near Harrogate, admitted assault occasioning actual bodily harm at an earlier magistrate hearing.
His sentencing was delayed until January 9, after Recorder Nicholas Barker told him he must prove he can work to pay the compensation to Ms Livesey or face a possible prison sentence.
"The charges do pass the custody threshold, but it would depend on the defendant's ability to work," he said.