The "pain-gate" theory says that the touch and pressure from cupping stimulate large nerve fibers, which results in the blocking of pain signals to the brain sent by other nerves. The gate control system is in our spinal cords. So, activating these nerve fibers can block pain transmission.
Does it work? One 2023 review of existing studies found that cupping seemed effective for managing chronic pain, knee osteoarthritis, low back pain, neck pain, and chronic back pain.