Background: Muscle explosive power as a component of physical fitness is an important factor that supports athletic performance in most sports. jump height and vertical jump performance in assessing explosive muscle power are influenced by various factors, including physiological, biomechanical, and anthropometric factors. Body mass index, muscle mass, and fat mass are important anthropometric factors in supporting jumping performance.Objective: To analyze the relationship between body mass index and muscle mass with legs muscle explosive power in first-year medical students of Diponegoro University.Methods: This study is an observational analytic study with a cross-sectional design. The subjects consist of 60 males and 108 females in first-year medical students of Diponegoro University who met the criteria. Body mass index and muscle mass were measured by Omron bioelectrical impedance analyzer, and muscle explosive power was measured by vertical jump test. Data were analyzed with the Kolmogorov Smirnov normality test and Spearman correlation test.Results: The average value of body mass index was 21.760±2.7734, muscle mass was 29.468±4.3283, and muscle explosive power was 29.468±4.3283. Muscle mass was positively correlated with legs muscle explosive power (p=0.00, R= 0.583) and negatively correlated between body mass index and legs muscle explosive power but it was not statistically significant (p=0.823 dan R=- 0.017) in first-year medical students of Diponegoro University.Conclusion: Muscle mass was positively correlated with legs muscle explosive power and body mass index showed no significant correlation with muscle explosive power. Keywords: body mass index, muscle explosive power, muscle mass, vertical jump test

Background: Overweight and obesity are two health conditions that contribute to the impaired quality of life. Two parameters of obesity also indicating body composition, body mass index (BMI) and waist circumference (WC), have been used as simple tools to assess abdominal visceral fats. The correlation between both measurements and visceral fats remains unclear.Objective: The study aims at demonstrating that body mass index and waist circumference may reflect visceral fats using bioelectrical impedance analysis in adolescents.Methods: First-year students of the Faculty of Medicine Diponegoro University participated in the study. This cross-sectional study measured BMI, WC, mid-arm circumference (MAC), and visceral fat (VF) of 130 participants. BMI, WC, MAC, and VF were assessed using Omron digital scale, measuring tape, and body impedance analysis, respectively. Spearman test was used for the bivariate analysis while multiple regression was employed to perform multivariate analysis. Significant results were determined if p value <0.05 for the bivariates.Results: The correlation between body mass index and visceral fats showed a strong value with r: 0.794 and p-value=<0.001. The correlation between mid-arm circumference and visceral fats showed r= 0.713 and p value=<0.001. Meanwhile the correlation between waist circumference and visceral fats showed r= 0.655 and p value=<0.001. BMI and WC showed the greatest correlation to VF. The comparison between genders resulted in men having stronger relationships between BMI and VF, and WC and VF.Conclusion: BMI and waist circumference are strongly related to visceral fats based on BIA in medical students.