其他摘要：Background It has been proved that physical activity has positive effects for all people. However, low activity is common among adolescents especially girl teenagers. The present study aimed to determine the condition of physical activity among girl adolescents by use of the stages of change derived from Trantheoretical model (TTM). Materials and Methods: This descriptive- analytical investigation was done (in 2016 and 2017 school year) in the first – round girl high school among 324 students studying in state schools of Shahrekord city (Western Iran). They were selected through clustering method. The data were collected by researcher-made questionnaires including demographic characteristics, knowledge construct and the stages of change (pre-contemplation, contemplation, preparation, action and maintenance). The collected data were analyzed by SPSS (version 18.0). Results The mean age of participants was 13.69+ 1.95 years old. The mean score of girls' knowledge about types of physical activity was 53.18± 21.82 (a total of 100 scores), which represents the average level of knowledge among them. The study of physical activity in students based on stages of change showed that 165 ones (43 %), 102 ones (26.6 %) and only 22 ones (5.7 %) of the studied students were in precontemplation, contemplation and maintenance stages, respectively. There was a significant relation between students' knowledge level and their mothers' age (P
