The term 'cause of back spasms' can be summarized by the crossword solution 'STRAIN'. STRAIN is a type of injury that occurs when muscles, tendons, or ligaments are stretched beyond their normal capacity. This can happen due to overuse, improper use, or sudden movements. Common causes of STRAIN include lifting heavy objects, repetitive motions, and poor posture. Back spasms can be caused by STRAIN, which can lead to pain and discomfort.