Relationship between joint motion and acceleration

Abstract. [Purpose] The purpose of this study was to clarify the relationship between acceleration and joint movement by synchronizing accelerometers and a three-dimensional motion analysis system, and to show the util-ity of an accelerometer as a postural control assessment tool. [Subjects and Methods] Head, lumbar, shank accelera-tions and various joint angles during single-leg standing were measured of 20 healthy males. Root mean squares of acceleration and joint angle were calculated. Fast Fourier transform analysis was performed for head, lumbar, and shank accelerations, and the median frequencies were calculated. Then, principal component analysis was performed for the median frequency of each acceleration. Stepwise multiple regression analysis was also used to examine the relationship between joint angle and acceleration. [Results] The score of the first principal component was highest for shank acceleration, while that of the second principal component was highest for lumbar and head accelerations. In multiple regression analysis, hip flexion/extension and adduction/abduction were identified as variables associated with head acceleration. [Conclusion] We were able to confirm the aggregation of acceleration into two components, which we interpreted as postural control strategies using primarily the ankle and hip joints. Furthermore, though multiple regression analysis, we were able to clarify the joint movement indicated by accelera-tion of each segment