.AlexX said:Rik's answer is good in terms of what has been done from the academic side of this. There was also an anecdotal "chart" done by some Olympic Weightlifting coach who basically took a bunch of Weightlifters weights with how much they were lifting for their bodyweight (I'll post it if I find it). As body weight increased from the lowest weight classes in Olympic lifters so did the amount of weight lifted per pound of body weight. This kept increasing until 170-180 lbs. where it began to decrease again. So the greatest amount of weight lifted, pound for pound, was in the 170-180 weight class.
There is also a lot of other anecdotal evidence that supports the idea that 170-180 is where the largest strength (once again pound for pound) is for the average person. On average most top sprinters are around 180 lbs. When gymnasts were 5''7-5'8 quite a few of them weighed between 170-180 lbs. John Gill was 180 lbs.
That's interesting, I wonder if this weight depended on height or not. I.e. would a 5'4" person be most efficient at 155 or 175?