treadmill

treadmill   

1 [ a piece of exercise equipment that has a large belt around a set of wheels, that you can walk or run on while staying in the same place 

2 [ work or a way of life that seems very boring because you  

 always have to do the same things
the treadmill of working

3 [ a mill worked in the past by prisoners treading on steps fixed to a very

in the office 

 large wheel