New ExerGame project titled Hanging Off a Bar.

Hanging off a Bar tires one out on the hands, arms and stomach quite quickly. Luckily, from time to time, there is a raft in the form of a set of logs coming by in the river, and the player can jump on these to rest and recover, but not for too long, because the raft disappears in the waterfall behind, and the player has to jump back up. - from Exertion Interfaces

See a video and read about it here

Image from Exertion Interfaces website