Being a swashbuckling leading man in Hollywood is tough work, which is why Clark Gable here, regularly engaged in physical training throughout his acting career. Not only that, but the posture, and body control developed from this training increased screen presence – Gable was one of the most popular actors of his time. The wall pulleys are likely from The Narragansett Machine Company.
This shot was taken in the Paramount studios gymnasium, circa 1937 (which was a barn on one of the back lots.) Steve McQueen was famously photographed training in the very same gym a few decades later.