The silver medalist wept as she recounted her ordeal at a press conference.
Guevara, a silver medalist in the 400-meter race in Athens in 2004, wept as she recounted her ordeal at a press conference, removing sunglasses to show her blackened right eye nearly shut.
The leftist politician denounced the attack as "an act of cowardice" and pleaded for an end to violence in Mexico.
"No to violence against women. This is an act of violence against my gender, against me," she said, flanked by Senate colleagues at the upper chamber.
Guevara, 39, said she was on a highway heading back to Mexico City on Sunday when she overtook a sport utility vehicle, which then struck her bike.
Guevara, who had a passenger on her motorcycle, said she had a shouting match with the driver when four men got out of the SUV and attacked her.
"I fell to the ground and the four began to kick me. One of the first blows is the one in my face. I went into a fetal position to try to protect myself," she said.
She was hurt to the degree that she needed surgery to put a plate on the right side of her face. She also had a fracture in her chest area.
She posted a picture of her facial injuries on Twitter.
The woman who was riding with her was also assaulted by the men, but not as severely.
The Senate called on authorities to find the assailants.
"I feared for my life," Guevara said, adding that she would post more pictures of her injuries every day.
Mexico is struggling to contain violence against women in some areas of the country. A "gender alert" was issued in the State of Mexico, which surrounds the capital, due to a wave of killings targeting women.
An average of six women are killed every day in Mexico, according to UN figures.