They could certainly dig, till or clean out stalls. I don’t believe they just had a few days off every month. Too many chores to be done.
http://yahshammahlove.sabbatarian.com/content/Niddah.html
In ancient times a niddah was completely segregated, particularly in Erez Israel where the laws of purity were still in vogue from the time when the Temple existed. Excluded from her home, the niddah stayed in a special house known as “a house for uncleanness” (Nid. 7:4), she was called galmudah (”segregated,” RH 26a), and was not allowed to adorn herself until R. Akiva permitted her to do so, that she might not be repulsive to her husband (Sifra, ;ora, 9:12). No food was eaten with a niddah (Tosef., Shab. 1:14) nor did she attend to her household duties, until the stage was reached in which “during all the days of her menstruation she is to be segregated” (ARN A 1, 4).