Figure 3. The change in principal components (PCs) and performance. (A) Abrupt changes in the directions of the PCs. Each vector denotes the first or the second PC. Sudden changes in the directions of both the first and the second PCs occur around the age of 50. (B) Gradual decrease in performance. The coordinate of the end point of each vector consists of the mean values of average speed in three track events. Aging gradually diminishes the magnitude of the vector, but hardly changes its direction.