A movement index termed balance strategy vector (BSV) was developed as a research tool for studying human balance strategies during goal-directed motions. For a given motion (motion capture data), the BSV index quantitatively represents its balance strategy by computing how available body joint DoFs’ angular motions affect the formation of the wholebody center-of-mass trajectory. The index facilitates easy and intuitive understanding of balance strategies of various human motions and can assist scientific investigations on human balance strategies. As an example demonstrating the utility of the index, the index was used to explore balance strategies of free-style, sagittal-plane load lifting motions.