Final answer:
In Pierce Brown's 'Red Rising,' Darrow uses the Stim Chair to work out during the Carving, a transformative process.
Step-by-step explanation:
The question refers to the science fiction novel Red Rising by Pierce Brown. In the novel, the character Darrow undergoes a process called the Carving. The machine he uses to work out and enhance his physique during this process is the Stim Chair. The Stim Chair is a device that stimulates the muscles for growth and development. It is designed to accelerate physical conditioning, helping Darrow transform into a Gold, one of the ruling class in the society depicted in the book.