Pelvic floor muscles (PFM) do not like the pumping movement of horseback riding, but they are activated by sitting on a saddle chair.
According to EMG tests, reaching down (to a low shelf, printer etc.) from a two-part saddle chair, over the supporting leg, is good exercise for the pelvic floor muscles.
It is beneficial to make use of this phenomenon. Big risk factor for weak pelvic floor muscles and "gynecology descend” is the pressure in the stomach area.
Sitting with poor posture increases this pressure and sitting with good posture eliminates it.