Hello, i know this is old thread but i feel like i might have an answer for the original question. I was struggling with the same. I am having huge issues with my left forearm pain. I went to couple of guitar teacher, they gave me similar advices to the above ones. Still, the pain was always there. Regardless how less force i would use on my fingers/fretboard etc.. So in my case the problem with the left forearm was my posture.
I keep guitar on my left leg btw, not that it would matter. this would happen if i would keep guitar on left leg or right leg. no difference.
For me it was my shoulders. I am not sure if you are also sick like me ( bechterew disease/zzsk ), long story short i have big issues with my back etc. So it could be the case why it is not that natural posture for me while playing.
My left shoulder when playing would lean forward (in the direction of guitar) too much.
You know if you are young and they tell you : 'wyprostuj sie/shoulders back' , when your nose is diving the ground. You you have to move your shoulders all the way back, to have straight posture. i will post a picture with my 'bad posture', and the 'good posture' so maybe it would give you better view.
All i have to do, is to keep focusing on my left shoulder to move to the back. By doing so , the wrist changes a bit posture as well.
When i do this i can practice 10-30 mintues, and i dont feel any pain. when i will forget about it pain will be back in 5 mintues.
The above posture will generate pain.
The below posture will not generate pain
What i am essentialy doing is this:
Give it a try, and let me know if that also helps you.
I completely realize this thread is old ,but i was googling about this today and found this thread ;) so i thought i would update it with my findings. I literally discovered this today. I can not stress out how happy i am !!!
edited
