THE DIFFERENCE IS IN THE ORICULO-VENTRICULAR APPERATURE. In the 60's runners ran with a lot more heart than runners run with today. We chased records. We did not WAIT until the final lap and then unlease a kick. I think when America went metric it hurt us a lot. The records, the how-to was all in miles. Switching to metric created a whole new set of records to run but no history to go with it. We lost our role models in the process.
There was a big feeling in the 60 of running for a cause greater than self. We ran to create greatness in other people. We role modeled the 70s & 80s. Now runners are more concerned with getting hurt than getting worthy of being the kind of person that could lead others. We are a nation of sheep!
Most of the great runners who came out of that era were actually wimpy. They were LESS than other people and through track found a way to try and become normal. In the process of becoming as good as others they excelled past everyone. Less is actually more.
Finally, we KNOW too much now days. We have books and sports reporters to tell us what can not be done. We have training methods to follow that will guarantee our mediocracy. We KNOW too much. If we could go back to the 50s and 60s and still have to chop wood every morning and feed the livestock maybe someone would come up mentally tough enough to get to the top. But so far few have shown any true courage. The books don't teach that.
Try go
www.gerrylindgren.com
and read that book. You will get a clear idea of what we lack now-a-days.