Punching bag
From Memory Alpha, the free Star Trek reference
A punching bag was a sturdy bag designed to be repeatedly punched for use in physical exercise or stress relief. Boxers commonly used punching bags for training.
Captain Benjamin Sisko used a punching bag (held by Jadzia Dax) to relieve some stress after Starfleet took him off of the Michael Eddington assignment – the first time in his career he had been taken off of an assignment. (DS9: "For the Uniform")
