The online feud between Twitter’s owner, Elon Musk, and Meta’s founder, Mark Zuckerberg, over their competing social media platforms, is escalating, with both men posturing online ahead of a potential cage match.

Mr. Zuckerberg on Tuesday posted a photo of himself training with the Ultimate Fighting Championship middleweight champion, Israel Adesanya, and featherweight champion, Alexander Volkansovski.

The photos came after Mr. Musk resorted to personal insults against Mr. Zuckerberg over the weekend, calling him a cuckold and proposing that the men compare the size of their genitals instead of fighting in a cage match.

Mr. Musk also suggested that the fight, which had previously been floated as a charity event, should be for temporary control of each other’s platforms.

“I have a proposal for Mr. Zuckerberg,” Mr. Musk said. “Winner of our fight gets ownership of the other person’s social media platform for 24 HOURS.”

Mr. Zuckerberg’s training photos appear to have come as a response to Mr. Musk posting training photos of his own earlier this month. The photo features Mr. Musk, a UFC hall of famer, Georges St-Pierre, podcaster Lex Fridman, and a jiu-jitsu instructor, John Danaher.

The dueling training photos, alongside photos from Mr. Musk’s vacation last year, have drawn widespread comparisons between the two men’s physiques.

Mr. Zuckerberg’s more athletic build, combined with the fact that he has more training in martial arts than Mr. Musk and is more than a decade younger, suggests that Mr. Zuckerberg could have an advantage in any physical contest.

After posing for the photo, Mr. St-Pierre said in an interview with the Sports Network that “I’m with Elon,” before adding that he hopes that the two do not end up fighting each other.

“We trained together and what I can say is that he is much stronger than the average man and he is very tough,” Mr. St-Pierre said. “He has a judo background.”

The 42-year-old fighter became involved in the spat between the billionaires after offering to help Mr. Musk as a training partner in a tweet shortly after the feud erupted.

“Even though I think he could do it, I hope this thing gets resolved in a different way,” Mr. St-Pierre said. “If he decided to get himself ready for something like this, that means he’s going to have to take time out of his schedule to do it.”

The president of the UFC, Dana White, has also hinted that plans for the cage match might already be in the works, telling the Sports Network that the men “100 percent” want to fight and that “I’ll announce it when we’re ready.”

In the background of the online back and forth between Messrs. Zuckerberg and Musk, Twitter is threatening to take legal action against Meta, complaining that Meta hired former Twitter employees that Mr. Musk fired when he took over the company.

In the week since Meta’s Threads launched officially, the social media platform has already amassed more than 100 million users. Twitter, for comparison, has about 450 million monthly users.

Neither the Ultimate Fighting Network nor Meta immediately responded to a request for comment. Twitter responded with a poop emoji.