It depends on how I feel. I rarely have cramps, so that is not an issue. However, sometimes I can be very tired so I'll either take it easy, or not do anything at all. Other times, like recently, I've been rocking it out with Cathe
. I think any movement can only help my fitness, but if I'm tired I need to rest. That can help my overall fitness too.
ETA: I used to take a week off during that time of the month, as it usually coincided with my planned rest weeks anyway. Now that my cycle has not been as predictable, I just go with how my body feels.