Calum, who finished in third place on the 15th series of the reality show almost two weeks ago, teased fans with the shirtless photo posted to Twitter.
He said: "Literally first day back in gym after a month in CBB house, it's needed and can't wait to crack on."
Calum made it to the final of CBB, losing out to runner-up Katie Hopkins and winner Katie Price.
Following his exit, Calum revealed he declared himself as single to land a spot on the show. However, during his stint in the house, Calum cryptically admitted to Cami Li that he was taken, and as previously revealed, his secret love is model and former Made In Chelsea star Ianthe Rose Cochrane-Stack.
And, despite Calum being involved in what has been dubbed 'the most controversial CBB series ever', he admitted to fans last night: "Funnily enough I miss that place #CBB."
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