There was a study done, where riders tended to adjust their stirrup leathers to a shorter length when they switched to using flexible stirrups, and even more so with stirrups that were both flexible and rotatable. This is in contrast to the longer length they were accustomed to with traditional stirrups—the kind that don't bend or rotate known as fillis stirrups. It seems that the additional movement allowed by the flexible and rotatable stirrups encourages riders to shorten the leathers for a better fit and greater control compared to the static nature of traditional stirrups.