George Hackenschmidt ran pain-free into his 80s. Squatting through a full range of motion builds the knees — the fix for runner knee pain and a core Running Ability target.
Three simple parameters: lift the heels off the ground, squat through a full range of motion, weight held behind your back — which shows you have full control.
Tested on the creator and many runners: 8 reps with 25% body weight loaded behind your back. Most runners can't do it yet — but you can build to it with pain-free training.