Are you a treadmill maniac? Personally I only choose to run when chased by viscous dogs. I especially hate running on a belt in a box like the dog Astro from the Jetsons.
It’s just NOT my thing. If I’m going to run I need some padding or the next day my knees will feel like someone was beating them with a ball peen hammer.
If possible try a Concept 2 Rowing machine, or something similar next time you’re at the gym instead of a treadmill.
But whatever equipment you’re on, are you actually exercising or are you trying to read a book? Get rid of the damn book. Focus on your pace and your heart rate. Start running in 30 second intervals where you go all out for 30 seconds and then slow down, but keep moving, for up to 1 minute.
When you’re recovered, no more than 60 seconds (not even 61 seconds), go back to your all-out sprint for another 30 seconds. Repeat this process 8 times. Be sure to spend a few minutes warming up and cooling down a slower pace.
Only do this if you’re in relatively good shape already. Otherwise you should start with 10-15 minutes of slower paced training on the treadmill.