As structures made of metal get smaller — as their dimensions approach the micrometer scale (millionths of a meter) or less — they get stronger. Scientists discovered this phenomenon 50 years ago while measuring the strength of tin "whiskers" a few micrometers in diameter and a few millimeters in length. Many theories have been proposed to explain why smaller is stronger, but only recently has it become possible to see and record what's actually happening in tiny structures under stress.

Read on the post is very detailed ... Does this apply to humans too?

Smaller is Stronger -- Now Scientists Know Why