This study examined age-related changes in dynamic balance (DB) ability, and the relationship between DB ability and isometric knee extension strength (IKES). Subjects were 100 females who regularly performed some light gymnastic exercises at a gymnastics club once or twice a week. Subject ages ranged from 20 to 85 years old. The measured items were height, body weight (BW), IKES, and DB ability. Results were as follows: 1. The average DB ability tended to gradually decrease as the subjects got older. There were some significant differences in the average DB ability between the 20 to 29 and 60 to 69 age groups, and between the 20 to 29 and over 70 age groups. 2. It was shown that there was a significant negative correlation between age and DB ability (r=0.471, p<0.001). 3. There was a significant negative correlation between age and IKES/BW (r=0.579, p<0.001). 4. It was shown that there was a significant positive correlation between IKES/BW and DB ability (r=0.368, p<0.001). 5. There was a significant negative correlation between BMI and DB ability (r=0.370, p<0.001). This study showed that DB ability rapidly decreased over 60 years old, and also the value tended to be higher in persons with a higher knee extension strength and lower BMI. Therefore, it was suggested that it is important to increase the knee extension strength and maintain an appropriate BMI in order to maintain DB ability.