Seen on a website that women who masturbate by tightening & crossing legs will end up making vagina loose. is this true or internet myth?

Myth: Pelvic floor muscle exercises (aka Kegel exercises), whether associated with masturbation or not, are beneficial in general and recommended for women after childbirth and with aging to help maintain "good" vaginal tone and prevent urinary stress and urge incontinence. Vaginal childbirth, aging, estrogen deficiency, repeated activities associated with straining associated with loss of vaginal tone.