My left hand middle finger tends to bend down (almost tucking itself under the bottom edge of the neck) as I play, especially when I am playing power chords and moving quickly across the fretboard. I feel that it is due to the increased pressure that I am applying with my other fingers to keep a clean tone while playing the chords across the fretboard. I know I should keep my left hand as relaxed as possible while playing and it seems like every other guitarist does it so naturally, but no matter how hard I try, my middle finger keeps bending down. I have noticed that this creates a lot of tension in my left hand, especially at the joints of my other fingers. It also causes my forearm to get fatigued after a couple of minutes of playing which prevents me from fingering the chords cleanly. I have no problem keeping my hand/fingers relaxed while playing open chords or individual notes.

I have tried playing songs slower so I can focus on my left hand positioning, but my finger starts bending down as soon as I speed back up. I have also tried to concentrate on keeping my middle finger straight as I am playing fast, but that makes my technique even worse because I am focusing relaxing my finger rather than applying appropriate pressure to the other strings; it also makes my forearm fatigue even faster since the struggle between flexing and extending my finger is using opposing muscle groups.

Does anyone know of any exercises that I can practice to help train my middle finger to remain straight while playing at faster speeds? Should I just go back to playing everything slow until my fingers get used to applying pressure to the strings without my middle finger bending?

Thanks!