Physical strength is the most important thing in life. This is true whether we want it to be or not. As humanity has developed throughout history, physical strength has become less critical to our daily existence, but no less important to our lives. Our strength, more than any other thing we possess, still determines the quality and the quantity of our time here in these bodies. Whereas previously our physical strength determined how much food we ate and how warm and dry we stayed, it now merely determines how well we function in these new surroundings we have crafted for ourselves as our culture has accumulated. But we are still animals – our physical existence is, in the final analysis, the only one that actually matters. A weak man is not as happy as the same man would be if he were strong. This reality is offensive to some people who would like the intellectual or spiritual to take precedence. It is instructive to see what happens to these very people as their squat strength goes up.
As the nature of our culture has changed, our relationship with physical activity has changed along with it. We previously were physically strong as a function of our continued existence in a simple physical world. We were adapted to this existence well, since we had no other choice. Those whose strength was adequate to the task of staying alive continued doing so. This shaped our basic physiology, and that of all our vertebrate associates on the bushy little tree of life. It remains with us today. The relatively recent innovation known as the Division of Labor is not so remote that our genetic composition has had time to adapt again. Since most of us now have been freed from the necessity of personally obtaining our subsistence, physical activity is regarded as optional. Indeed it is, from the standpoint of immediate necessity, but the reality of millions of years of adaptation to a ruggedly physical existence will not just go away because desks were invented.
Like it or not, we remain the possessors of potentially strong muscle, bone, sinew, and nerve, and these hard-won commodities demand our attention. They were too long in the making to just be ignored, and we do so at our peril. They are the very components of our existence, the quality of which now depends on our conscious, directed effort at giving them the stimulus they need to stay in the condition that is normal to them. Exercise is that stimulus.
Over and above any considerations of performance for sports, exercise is the stimulus that returns our bodies to the conditions for which they were designed. Humans are not physically normal in the absence of hard physical effort. Exercise is not a thing we do to fix a problem -it is a thing we must do anyway, a thing without which there will always be problems. Exercise is the thing we must do to replicate the conditions under which our physiology was adapted, the conditions under which we are physically normal. In other words, exercise is substitute cave-man activity — the thing we need to make our bodies, and in fact our minds, normal in the 21st century. And merely normal, for most worthwhile humans, is not good enough.
Training for Strength is as old as civilization itself. The Greek tale of Milo serves to date the antiquity of an interest in physical development, and and understanding of the processes by which it is acquired. Milo is said to have lifted a calf every day, and grew stronger as the calf grew larger.
The progressive nature of strength development was known thousands of years ago, but only recently (in terms of the scope of history) has the problem of how best to facilitate progressive resistance training been tackled by technology… Properly performed, full-range-of-motion barbell exercises are essentially the functional expression of human skeletal and muscular anatomy under a load.
source: Starting Strength by Mark Rippetoe