A little confusing, do you mean a uterine prolapse? You'd only have a vaginal vault prolapse after hysterectomy.
Assuming you've not had a hysterectomy then a pessary may not work that well for you. If a ring pessary is used it's likely the womb/cervix will drop through the middle of the ring, using a ring pessary for short periods isn't likely to cause you any harm but I'm not sure how effective they will be. Shelf or gel horn pessaries used for uterine prolapse are more secure but can be very difficult to get in and out. Have you tried using a large tampon instead, they can be very effective at providing gentle support during exercise.
These temporary supports are fine when prolapse symptoms are intermittent or linked to specific activities but when symptoms are more persistent as they eventually will be then do your research regarding operative repair, avoid hysterectomy and look carefully at Sacrohysteropexy. You'd be surprised how effective, simple and safe it is.