Access to a gym in Paris near Luxembourg RER
My boutique hotel in the 6th Arr in Paris is about a 5 minute walk north of the Luxembourg RER station and has no workout room. I have spondylolisthesis which is a lower back condition. If possible in each of the 4 full days I'll be in Paris, I would like to go to a gym in the morning for an hour to do stretching and abdominal strength training exercises using a big rubber exercise ball, a table and access to a big gym mat. I can always shower in my hotel room; I just want a place to do my exercises and strength training near my hotel.
Does anybody have an recommendations and an idea of the cost per day? Thank you very much.