How to play static dominant and functional dominant chords?

How come when I play barre chords on guitar, the lower part of my thumb hurts?

• when im playing barre chords the lower part of my thumb hurts like the muscle part of my palm I know it has something to do with me pressing my thumb down on the neck of the guitar. I know how to play barre chords i can play them and switch'em up and everything without struggling at all whatsoever. But when im doing non-stop barre chords for like ten minutes like just practice them my thumb hurts really bad in complete agony where i cant take it and cant even do power chords without keeping my thumb up where im not even putting any pressure down i tryed tunning my guitar down 2 steps where the strings are loose (but with my gauge strings not too loose) and after a lttle bit my thumb starts to hurt still I also tried using an electric guitar and still the same I asked another guitarist who has played only acoustic and been playing since he was in the 3rd grade and he didn't even know anything that would help. I also looked onher forums and other poeple people are having the same exact ploblem but the only answers they get is stuff like check your techniqe, its because its an acoustc the strings are raised up higher, you just need to practice, i dont know what to do im pretty sure I dont need to just practice getting the muscle in my stronger because by the time i would be done i'd be able to break peoples arm with just my thumb and I dont think im doing anything wrong with my "technique" im holding my thumb down on the back of the neck and im barring with my index finger though after my thumb starts hurting it kinda feels like I was put'n some real pressur on the neck but i dont think I was doing that,that much can anyone figure this out its not the first time i've had this problem

• Answer:

  Then you're doing it wrong! You shouldn't be putting any significant pressure on your thumb. You're not trying to push the fretboard into your fingers with your thumb. You're supposed to push the strings down with your fingers. It takes time to develop those muscles in your hands, but in the mean time you can't try to take some cheap way out and use your thumb. You can cause yourself significant injury like that.