Why do my stomach muscles go crazy when stuttering?

Why do my stomach muscles go crazy when stuttering? I went to physiotherapy a few days ago. I was laying on my back, and when I was making small talk with the therapist, I realized my stomach would fidget like crazy while and right before I stutter. It felt like I was sporadically pulling in and pushing out my stomach. Not sure if anyone else has experienced this, but I was wondering if learning to manage this might help with my stutter. Thanks!