Moustafa “Big Mo” Ismail, 24, says his biceps are 78cm through sheer hard work, pumping iron twice a day, reports Ninemsn.

His biceps were awarded the accolade of being the biggest in the world by Guinness World Records last week but his unnatural proportions have raised doubt, so Ismail’s title is now being reviewed.

“Regarding the record for ‘Largest Biceps’, Guinness World Records is conducting new research with medical specialists to review this category and determine whether we may need to make any changes to the outcome of the record,” said Guinness World Records spokesman Chris Sheedy

Mr Sheedy said Guinness had not run tests on Ismail to determine if his muscles were achieved naturally because “our role, so far at least, is simply to record extremes”.

“One of the biggest issues for us is that the public naturally expects Guinness World Records to report all extremes,” he said.

“So the largest upper arm circumference on a human being is of interest biologically and we are expected to know who those arms belong to.

“Of course, at the time of measuring we believed Mo had not been utilising any performance enhancing drugs, and he still very publicly claims this to be the case.”