In my opinion Charlie Francis is probably the best sprint coach that ever lived. The coach of Ben Johnson and other great athletes.
His short to long coaching methods and his uncomplicated approach have influenced coaches all around the world. Below is an extract from an article I read which jumped out and rang so true for me.
Another confirmation of his exceptional observational skills would be revealed in conversations with the athlete the next day. We would find out that the athlete had some muscle soreness or tightness in the exact area where Charlie Francis suspected the problem started – almost in a David Blaine-like exhibition of magic. This is a difficult concept for many coaches to grasp, particularly if they are stubborn about sticking to their training plans, regardless of what they see with their own eyes.
If an athlete is fatigued, no level of extra work is going to make them better. In many cases, it will make them worse.
Charlie had a firm grasp of the concept of stress and adaptation and how it related to the various athletes under his supervision. He was like an artist who knew exactly how much paint to leave on the canvas or how much stone to chip off a sculpture, when others would be slathering on the paint or taking a jackhammer to the work. However, like an artist, it takes a good amount of experience, discipline and self-security to determine the optimal amount of work on the day. While modern day coaches are hoping to rely on iPhone apps and other diagnostic technology to evaluate their athletes, Charlie simply relied on the powers of observation.
from Running Mechanics