There is no 80/20 rule in running.
Running has no shortcut, no lifehack, no minimum effective dose.
Running performance is directly related to the number of miles ran.
Sure, there are optimized training plans. Rotating intervals, short runs and long runs creates better results than running medium length runs. The training plans still require weekly mileage goals.
The only way to prepare for a marathon is to run a lot of miles. Spending only 4 hours a week on running will not be enough. The body needs to learn how to run long distances. It takes miles and time to build the muscle and cardio necessary for long runs.
This is great news to me. To run well I have one simple decision to make.
Do I run a lot of miles this week?