"... We are so inactive these days and have been since the industrial revolution really kicked into gear," McAllister replied. These people were much more robus

"... We are so inactive these days and have been since the industrial revolution really kicked into gear," McAllister replied. These people were much more robust than we were. ... Generalisation but I tend to agree as I go off and do my 970/1000Km pt this year in an experiment in failure. I want to see how hard I can repeatedly push myself before I crack, 10Km at a time. Haven't yet. The insights have some implications for motivation, completion of tasks and failure. "... The human body is very plastic and it responds to stress. We have lost 40 percent of the shafts of our long bones because we have much less of a muscular load placed upon them these days. 'We are simply not exposed to the same loads or challenges that people were in the ancient past and even in the recent past so our bodies haven't developed. Even the level of training that we do, our elite athletes, doesn't come close to replicating that. ..." The question is do you want to? I know people in trades, hard manual labour do this kind of level of exercise and work. The mulsular-skeltal system simply wears out. You're fitter but more worn out.