When Martin got out of the coaching business because he was too busy with his own training, he passed several of his clients on to Daniels. Two of them lived in Santa Cruz, California. Daniels notes that the only time he saw them in person was for 15 minutes in the San Francisco airport while he was en route to Hawaii. Daniels normally works with elite athletes, but also enjoyed working with people of lesser talent, which he felt offered a different challenge. Daniels, who did his doctoral dissertation testing swift Olympians such as Jim Ryun, George Young and Bob Schul, stands among the top ranks of exercise scientists.
Some people try.
Their experience may be limited to their own case, and they're not observant of others. A coach can bring information from a great number of sources and explain why something works and why something else will not. It is then that they need someone to bounce ideas off, as well as someone to moderate the intensity of their efforts. First, you need to do more and more work for increasingly smaller gains in fitness. So the injury risk is very high, the burnout rate is very high.