When runners tire, they often overstride, which exaggerates their knee lift. But lifting your knees just tires out the quadriceps even more quickly, leading to sore thighs the next day. Your knees should primarily swing forward and back not pump up and down. If your knees are lifting up instead of swinging forward:
1. Reduce the length of your stride.
2. Keep your feet low to the ground.
3. Maintain a quick stride rate, just lightly touching the ground with each footfall.