Yet tests showed that a gram of their muscle was less powerful than the same amount of tissue from someone who did not weight train.

Lead scientist Professor Hans Degens, from Manchester Metropolitan University, said: ”Most of us are impressed by the enormous muscle bulk of bodybuilders and think that these people must be extremely strong, like the ‘Incredible Hulk’.

”The surprising thing, however, was that a gram of muscle from bodybuilders produced less force than that from non-bodybuilders, and it thus seems that the ‘muscle quality’ is less in bodybuilders.

”It appears that excessive muscle growth may have detrimental effects on the quality of the muscle, and one may well be better off with normal-sized muscles than with metabolically expensive large muscles.”