HAH!!! Thats a hilarious rule.For the benefit of those who reported this post, were silently offended, etc., der_kluge was referencing one of the worst RPGs ever made, F.A.T.A.L., which actually included such a rule.
From the infamous RPGNet review:
It IS terrible though. Not realistic. Muscle mass generally correlates positively with intelligence. Albeit weakly. I suppose the idea is that being mentally retarded can cause bursts of strength where the brain doesnt restrain the body's full potential or some other anime logic.