Does posture affect the game?
Assuming you are talking about yourself while playing a video game in question and not your player model in the game (crouching, fashion trend, etc.), then my experiences, seems to affect the posture score. I always travel during I play; postures promote different intensities of play. When I slouched back, I find my fingers are less dexterior and my reactions are slower, which causes a relatively low score, which is even lower if I decide to stop. Sitting with my hands in front of me, I can play freely with nothing except my Mad Skillz. My tendons are loose and flexible, allowing a maximum range of motion. I hope I answered your (very vague) question.
Awesome Video Game Music 101: The Posture you do not despise (Eternal Sonata)