When i play solos or some relatively fast lines I feel a pain on my right arm. More precisely it's around the brachialis m. This happens both when i play standing or sitting. In the latter case, changing position from standard (guitar sitting on the right leg) to classical position helps mitigating the pain. I don't know if a poor picking technique can justify the pain; maybe my right arm is too much tight when I play. Don't know if you have experienced this or have some tips to fix the pain/playing.