What are possible reasons that my fibromyalgia flares up when i'm in a car?

Greater Muscle Spasm: Fibromyalgia pain worsens w. auto trips, as mechanical jostling causes strain of chronically spastic torso, back, & pelvic muscles. In my opinion, chronic muscle spasms are compensatory efforts to maintain rigidity of an unstable musculoskeletal system; secondary to sacroiliac joint ligament laxity from trauma, childbirths, or genetically-potentiated Hypermobility Syndrome. Gravity Rules.