Treehugger report that "The punching bag is, in actuality, a very clever ad campaign by Adidas, installed in Shanghai. The slogan written on it, according to Micgadget, says, "Every year you have to wait on the platform for about 1,824 minutes. Don't waste your time, come and have some punch !"
We know there can be a lot of waiting on a Tube station platform. It might not a bad way to get some exercise or blow off some steam while waiting. Fun installations like these are definitely a way to get people to try to enjoy the daily commuting grind a little more. The recent slide installed in Overvecht is a great example of this.
However, there are obviously downsides to the punch bag idea. Dvice points out, "Now, I understand there are droves of stressed out workers going to work and returning home in China, like there are in every other major global city, but a subway station doesn't exactly seem like the best place to install a punching bag. One blown nerve and a person taking it out their virtual boss on the bag could end up accidentally injuring a bystander."