During a womens menstrual cycle, the man or women may suggest to the other they 'go off-road'.
This means to engage in anal sex in order to avoid having sex via the vagina during her period (bloody mess).
Many couples enjoy this alternative with the aid of a water-based lubricant.
If you want to be more romantic you can always ask in French would you like to "aller tout-terrain"?
Off-road season is a chance to explore another side of your sex life. Enjoyment for the man and the woman.