I found these lovely clubs in pictures of old time strongmen and decided to investigate. It appears that these fairly light clubs (only 2lbs each) were used in some sort of a combination flexibility and aerobics class. While many practice them alone at home, it was also popular to practice them in groups!
I have been doing some basic movements with them and while it does not feel tremendously taxing, it created a great deal of soreness in my shoulders and wrists. My wrists will need time to catch up to this type of flexibility and exertion but that does not bar the more 'locked' types of movements. These bend at the elbow when needed but most of the flexibility comes from the shoulder girdle. It seems to me that the shoulder girdle is the most intensely and completely worked area following an Indian club workout. Combined with kettlebells, these are the perfect upper body flexibility compliment.