I play guitar and I should have my fingers directly above the frets when placing all four fingers down. But if I curl them just a bit, I cant spread the middle finger and ring finger AT ALL. They are touching, and apart from spreading them from my other hand, they just wont move. I'm sure this is somewhat common, but is there anything I can do about it ? I've read that walking around with something in between might help but can be really bad for your tendons. Thanks
That's just how the hand works, and you should not apply force to change it! The solution for reaching the required positions is to rotate the hand away a bit from a perfectly perpendicular position. Observe how violin players do it, and do it a bit like that. (Violin has no frets and therefore precise positioning is essential).
Here's an answer I gave to a very similar question sometime ago:
If your hand is curled too much then no, you won't be able to spread your fingers.
Quick test, no guitar required - hold your hand up vertically in front of your face, fingers & thumb straight up, palm facing you. Spread your fingers. Oppose your thumb as though you were going to grip something [like a guitar neck], then start to bend your fingers, keeping your thumb in the same position.
As you close up, you'll see that even though you can keep your knuckles apart, your finger-tips will eventually close in til they touch. At that point, with no external force, you're stuck.
Somewhere between those two extremes is where you need to be to play.
Dropping your elbow &/or lifting the guitar neck will make that middle ground easier to achieve.
Also note that if you twist your hand to the right, you can spread your fingers along the fretboard by straightening them to different degrees.
A combination of these two 'tricks' should help your reach.
If you play with your thumb hanging over the top of the fretboard, this will cure you of that too ;) You have to drop your thumb to the centre of the neck to do this.
Another 'fun' trick, not really related but which demonstrates how the tendons of your 2nd & ring fingers are intertwined…
Place both hands together in front of your face, fingertips touching to make a 'steeple' shape [Think Monty Burns' "Excellent" pose]
Bend your two 2nd [middle] fingers until the 2nd knuckles are touching, this will make a kind of 90° angle, pointing down. Keep the rest of your fingers steepled.
Tap your first [index] fingers together.
Tap your little fingers together.
Tap your ring fingers… nope, no can do.
Try experimenting with your left hand pulse+thumb. The more straight angled your pulse is, the easier your fingers can spread. But the thumb behind the guitar neck must find a good position to support the presure from your other 4 fingers at the oposite direction. Try playing without your thumb to feel how important it is