" In conclusion, human bodies were not engineered like the Brooklyn Bridge but instead evolved to grow by interacting with their environment. Because of millions of generations of natural selection on these interactions, every body needs appropriate, sufficient stresses to tune its capacities. The old adage “no strain, no gain” is profoundly true. Allowing our children to ignore this adage leads to a pernicious feedback loop in which problems like osteoporosis become more prevalent, especially as people live longer. Maybe "

― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease