Sen. Bernie Sanders may have to prepare to take hits from sources other than his 2020 rivals after getting a shot from a speed bag over the weekend.

The Vermont independent paid a visit to the Muhammad Ali Center in Louisville Sunday. Vice DC Correspondent Elizabeth Landers reported that Sanders joked to his staff that he may need to take out his "damn aggression" on the speed bag display.

However, when Sanders took a swing at the speed bag, he didn't expect the bag to swing back.

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The video prompted strong reactions on Twitter.

"This wouldn’t exactly strike fear in the minds of our adversaries. Imagine this guy sitting across the table negotiating with world leaders?" Donald Trump Jr. tweeted.

"Speed bag meet wind bag," Fox News host Laura Ingraham quipped.

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Perhaps boxing isn't his sport, but Sanders recently displayed his softball skills during a ball game with his campaign staff earlier this month in Iowa. He was also filmed shooting hoops in a New Hampshire high school gymnasium the night he defeated Hillary Clinton in that state's 2016 presidential primary.