I also held several masters running titles.
Intervals and other types of speed work are essential to improve running speed.
Again, racing for me was about energy management.
There's always the feeling of getting stronger. I think that's what keeps me going.
You have to know your body. It's part of the beauty of the training process, and once you've determined how much your body and mind can take, you can then begin to reach your potential.
I started in law school in '71 and graduated in '74. So I was training for the Olympics, running or averaging around 20 miles a day and going to law school full time.