Abstract: Agility is a form of human movement and plays an important role in the matches of team sports, racket sports and combat sports. However, agreement has not yet been reached onthe definition and testing of agility in sport science. We reviewed the literatures involving definition and testing of agility in sport. Based on the current knowledge in the literatures, we proposed a more comprehensive definition and pointed out several challenges faced by the existing agility tests. Agilityis defined as the ability to quickly, accurately and efficiently change and adjust the movement mode (i.e., changing motion) or state (i.e., changing direction or speed) according to the aims (either pre-planned or unplanned) during the human movement. Although most of tests in the literatures had good reliability and validity, there were four major challenges including lack of gold standard test, overweighted running in straight line during the test, limited attentions on the quality of motion, as well as difficulty in comparison between different tests. The future researches about agility could be promoted from the following aspects: to use the wearable devices for quantification of agility, to investigate the influencing factors of agility and develop corresponding training methods, to examine the effect of agility training on improving performance and reducing the risk of injury, to explore the sensitive period of agility development.

Key words: agility, change of direction, cognition, testing, physical fitness, ability, movement