Functional fitness age (FFA), which we previously described, is a measure of functional age that reflects a person's overall physical ability to complete daily tasks such as preparing meals and performing various household chores. The purpose of this study was to validate FFA in two elderly populations: 1) older subjects from different communities, and 2) older subjects participating in an exercise intervention program. FFA was calculated from 4 performance tests: performing arm curls; moving beans with chopsticks; demonstrating functional reach; and sitting and walking around two cones. The first study group was selected from 4 different communities (N=127), and was subdivided into a less active group (N=87) and an active group (N=40). The results of the 4 tests for the less active group were not significantly different from those for the original validation group used in developing the FFA equation. The FFA of the less active group (71.1+/-7.7 yrs) was not different from their chronological age (70.4+/-6.6 yrs). In the active group, except for the arm curls, test scores were significantly higher than those of the original validation group. The FFA of the active group (66.2+/-5.1 yrs) was significantly younger than their chronological age (70.9+/-4.2 yrs). Another group of 14 older women (79.5+/-3.9 yrs) was recruited for pre- and post-training testing. After the 3-month exercise program, they showed significant improvements in sitting and walking around two cones and functional reach; their FFA decreased significantly from 81.5+/-5.0 yrs to 78.3+/-4.5 yrs. The control group selected from the same community (N=16, 79.8+/-5.3 yrs) showed no significant changes in the 4 performance tests, and their FFA remained unchanged. These results indicate that our FFA is highly cross-validated for different Japanese communities, and is sensitive to changes associated with participation in an exercise intervention program.