Effects of different movement strategies on forward reach distance

The functional reach test (FRT) is a reliable and frequently used test to measure dynamic balance ability clinically. However, it is not clear if reach strategy would affect the association between reach distance and dynamic balance. The purpose of this study was to investigate the extent to which reach distance reflected dynamic balance in different reaching strategies. Thirty-three healthy young adults performed the FRT that required subjects to stand with the feet shoulder width apart and one arm raised to 90°, and then reach forward as far as possible without moving the feet or losing balance. Two additional instructions were given to induce different strategies: keeping the raised arm at 90° throughout the test, and reaching toward a shoulder-height target. The kinematics was recorded using a Vicon motion system, and the hip, ankle and mixed strategies were identified. The results showed that subjects adopted different strategies during the FRT. Significant correlations were found between reach distance and center of mass displacement in the ankle, and mixed strategies. Reach distance, hip posterior displacement and angular displacement of the trunk, hip and ankle were significantly different between the hip and ankle strategies. These findings show that the extent to which reach distance reflected dynamic balance was affected by the reach strategy adopted. It is suggested that clinically, both reach distance and movement patterns should be given special attention when conducting the FRT.