Former Boston firefighter Albert Arroyo was acquitted of fraud charges by a federal jury yesterday. The charges were brought against Arroyo for engaging in a bodybuilding competition and other strenuous activity while on disability leave for work-related injuries.

The not guilty verdict on two counts of mail fraud shook Arroyo, who quivered with emotion, bowed his head, and burst into tears, reported the Boston Globe.

“We’re extremely gratified that the jury was able to consider all of the evidence and put aside the public outcry,” said Timothy Watkins, Arroyo’s attorney, after the verdict was read in US District Court in Boston. “The public didn’t know the facts. The system worked.”

In a statement, US Attorney Carmen M. Ortiz said the verdict was a “disappointment.”

“Taxpayers expect an honest day’s work for a fair day’s pay from every public servant,” she said. “We will continue to investigate and prosecute allegations of these types of frauds.”

Arroyo was fired for refusing to return to work as a fire inspector after officials leant that he was competing as a bodybuilder.

“Mr. Arroyo was terminated from the city of Boston,” said Dot Joyce, a spokeswoman for Mayor Thomas M. Menino. “He was terminated because the city of Boston contends he was able to do the duties assigned to him. He was ordered to return to work and refused. He no longer works for the city of Boston.”

Eugenia M. Carris, Assistant US Attorney, told the jury that Arroyo knew how to abuse the system and used his knowledge of how to file false disability claims in a scheme to defraud the city.

On the other hand, Watkins, a public defender, argued in his closing that prosecutors had failed to prove their “theory of calculated fraud and manipulation beyond a reasonable doubt.”

Carris had reminded jurors that Arroyo had complained his back problems were so bad he had trouble lifting a piece of paper. At the same time, she noted, he was working out twice a day, at times using dumbbells to squat more than 200 pounds.

Carris said that after his injury in 2000, he was returned to full duty, but he was accommodated and given a relatively light job as an inspector in the fire prevention office. At a time before his 2008 injury, he had claimed to be in physical therapy when he was actually training for bodybuilding competitions, allowing him to leave work early twice a week, she said. She noted he said he couldn’t sit for longer than a half hour without back pain, while he made repeated trips to New York to buy vitamin supplements.

Lastly, she said Arroyo gave inconsistent accounts of his March 2008 fall at a vacant firehouse in Jamaica Plain, the alleged injury he used to seek disability. She said he told some people he slipped while going down the stairs, while telling others he fell while going up the stairs.

“He needed something new to happen, the kind that gets you the most money and tax benefits,” she said.

Arroyo was a firefighter for two decades when he applied for accidental disability retirement. He was caught on video flexing his muscles in a strenuous routine at a bodybuilding completion in Marlborough, six weeks later.

Arroyo could have faced up to 20 years in prison for each count of mail fraud.