My introduction to running was by way of a Couch – 5K plan I found on the Internet, followed up with a beginner's marathon plan by the great Hal Higdon.
Soon after that I came across Matt Fitzgerald and his 80/20 plan. Slowing down sounded like a good idea, so I went with that. It was through Matt that I discovered Dr. Stephen Seiler, credited with formulating 80/20 training. At some point I learned that Joe Friel was another Seiler fan. He was the one who said that too often athletes make their easy days hard and their hard days easy.
Then came the debate about what constitutes a hard workout. In one of his YouTube posts, the highly respected Ironman athlete and coach Mark Allen made it clear that to be low intensity a workout – in particular, a long bike ride – must never include any high intensity efforts. His position was that the body remembers the effort, and when the time comes to respond to the training stimulus it gives priority to high intensity effort. If you slip into zone 3 or 4, the impact of that five hour zone 2 ride will be greatly diminished.
I cannot find anyone who agrees with that. In fact, what I often hear is the exact opposite, especially for age-groupers with limited training time. If you can’t take the time to do a long, easy four hour ride, but can do two hours, then add some intensity somewhere in there. Not a lot. Keep most of it easy. Don’t ride the whole thing at the limit, just a little. For swimming, which places so much less pounding stress on the body, include some intensity in almost every swim. Maybe hold onto one long swim per week at a really easy pace. Running is tricky because of the significantly higher risk of injury. In triathlon training we can shift some of the aerobic development to the bike, so the weekly mileage we expect from pure runners is not only unnecessary, but dangerous.