PURPOSE The purpose of this study was: (1) To investigate the network evolution processes to understand research trends in physical activity of older adults and (2) To examine the contribution of keyword and keyword aggregation groups to the knowledge structure of physical activity of older adults. METHOD This study is conducted to search journal articles on NDSL site to identify research trends related to physical activity of older adults. To achieve this goal, we performed semantic network analysis on 1,170 papers of 162 international journals related the studies on physical activity of older adults, which were published between 1990 and 2019. The Net-Miner was employed to conduct the semantic network analysis. RESULT The results are as follows: First, there appeared little change in the research trend related the studies on physical activity of older adults. Although slight cyclical changes were found, there was no significant paradigm shift. Second, in the past 29 year, only a few key words in the study of physical activity of older adults have contributed to the formation of intellectual structure. These key words represent the research trend in the field of physical activity of older adults. CONCLUSION There has been no significant change in the physical activity research area of older adults over the last 29 years. A challenge to new research on physical activity of older adults is needed. In addition, a few core keywords are very important for research in the field of physical activity of older adults.