Chess is a game that requires critical thinking, analytical skills, and strategy making. It is not just a leisure activity, but also a mental training exercise that can improve cognitive abilities. However, if you are looking for synonyms for the phrase "chess as mental training," terms like "brain workout," "intellectual exercise," "mind games," "cerebral exercise," or "mental gymnasium" might be useful. These phrases also imply that chess is more than a simple game, but a way to sharpen your thinking skills, boost concentration and memory power, and promote problem-solving abilities. Therefore, if you want to improve your mental agility, consider playing chess or other cognitive activities that challenge your brain.