Coach Christensen describes the approach needed to successfully develop the 400 meter runner moving up to the 800 meter event, aka the Type 1 800 Meter Runner.
Is it important as a middle-distance runner (specifically 800m
Interval Workouts: 4 Interval Training Workouts for Runners
Technique: Analysis of Usain Bolt's Running Technique
Middle Distance Training Guide
800 Meters
5 Running Workouts to Get Faster — Runstreet
Records Fell at the Track Worlds. A Trend? Not So Fast. - The New York Times
400 Meter Training Workouts for Sprinters
The 800 Meter Runner: Speed (Type 1) - Complete Track and Field