Alif Febrianto: The Effect of Nutritional Status, Physical Activity, and Family Support on the Physical Fitness of Elementary School Students in Tongkuno District, Muna Regency, Southeast Sulawesi. Thesis. Yogyakarta: Master Program of Physical Education, Faculty of Sport and Health Sciences, Yogyakarta State University, 2026.

This study aims to determine: (1) the effect of nutritional status on physical fitness, (2) analyze the effect of physical activity on physical fitness, (3) examine family support in influencing physical fitness, and (4) the simultaneous influence of nutritional status, physical activity, and family support on the physical fitness of elementary School Students in Tongkuno District, Muna Regency.

This study uses a quantitative approach using a cross-sectional design. The population in this study were elementary School Students in Tongkuno District, Muna Regency. The sample used was 245 students selected using cluster sampling. Nutritional status was measured using the body mass index for age (BMI/A), physical activity was measured using the Physical Activity Questionnaire for Older Children (PAQ-C), family support was measured using a questionnaire based on Cohen, Wills, and House's social support theory, while physical fitness was measured using the Indonesian Student Fitness Test (TKSI). Data analysis was conducted descriptively and inferentially using multiple linear regression with the help of SPSS. 

The results of the study were as follows: (1) nutritional status had a positive and significant effect on students' physical fitness (β = 0.272; p = 0.000), (2) physical activity had a positive and significant effect on students' physical fitness (β = 1.423; p = 0.000), (3) family support had a positive but insignificant effect on students' physical fitness (β = 0.020; p = 0.370). (4) Simultaneously, nutritional status, physical activity, and family support significantly influenced students' physical fitness with an F-value of 75.805 and a significance level of 0.000.