I can run a 5K in 17 minutes.
But today’s 15K was at 6:00/km.
Most of my training is slow — on purpose.
Slow long runs build your aerobic base, improve endurance, help recovery, and reduce injury risk. They’re what allow you to actually handle hard sessions.
I wouldn’t be running sub-20 (or 17) minute 5Ks without years of easy miles.
Run slow to run fast.