Trunk extension is a term used to describe the act of extending one's trunk, or torso, in order to increase flexibility and range of motion. It is commonly used in physical therapy and exercise programs to improve posture, balance, and coordination. LIMB is a four-letter word that refers to any of the appendages of the body, such as arms, legs, and fingers. Trunk extension exercises involve stretching and strengthening the muscles of the torso, which can help improve overall body strength and flexibility.