Originally Posted by: osmanitellezBasically the guitar tends to move a lot when changing chords, specially between bar chords and open chords. It happens even more when standing but sitting as well.[/quote][p]Three things will fix this: good posture, a properly adjusted strap, good technique.
[quote=osmanitellez]I am trying to figure out what keeps the guitar still and in place as we change chords, looking into my physicallity and tension.
Use less tension, stay more relaxed. Also, use minimal motion. The wider, bigger, stronger your motions are while changing chords or strumming the more you are likely to move the guitar around too much. Too much motion & tension also hinders your ability to get to the next motion (note, chord, change, strum, etc.) on time.
Hope this helps!