**2.5 Leg power testing**

Leg muscle power, a component of muscle fitness was assessed using a vertical jump (VJ) field test. The test was conducted indoors on a flat floor with a smooth wall using the countermovement jump (CMJ) protocol. Participants were instructed to rub chalk on the fingertips of the dominant hand and had a couple of practice sessions and then took their turns for the test. In the CMJ protocol, a participant stood with the dominant shoulder about 15 cm from the wall with both feet flat on the floor, reached as high as possible with the dominant hand, and made a chalk mark on the wall. He/she lowered the dominant hand, performed a countermovement by flexing the knees and hips, moving the trunk forward and downward and swinging the arms backward, and jumped with a swiping motion as high as possible making a second

mark on the wall. The score was the vertical distance between the two chalk marks. Participants' scores were converted into VJP values using a regression equation [15]. Each participant was given two trials and the best recorded to the nearest centimeter. Detailed description of the protocol is available elsewhere [16]. Participants were categorized into high and low groups using their sex-specific VJP receiver operating characteristic (ROC) cut-off values.

### **2.6 Blood pressure measurement**

Blood pressure of participants was assessed in the morning while they occupied a sitting position after 10 minutes of rest with an oscillometric device. (HEM-705 CP, Omron Tokyo, Japan). The resting systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored on each participant's right arm using appropriate cuff sizes. Measurements were taken 3 times at 2-min intervals, and the average was recorded. Specific details of the BP protocol have been previously described [7]. The cut-off points for HTN (95th percentile for age and sex) in this study were based on the standards of the fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents 2004 [17].

### **2.7 Data analysis**

Data were checked for normality before analyses with the Kolmogorov–Smirnov test. Complete data for all variables were available for 2047 out of 2100 adolescents, with a compliance rate of 97.5%. Descriptive statistics were presented as means ± SDs, frequencies, and percentage distributions. Student's t-test was used to compare the means of both genders on all study variables. Zero-order correlation coefficients were calculated to assess the relationships among BMI, VJP, and BP of participants. Multiple linear regression analyses were conducted to determine the independent and combined associations of BMI, VJP, and resting BP. All analyses were adjusted for biological maturation. Biological maturation was estimated from height and chronological age using the regression equation of Moore and Co-workers [18]. The equation estimates maturity offset (MO) directly. Then, age at peak height velocity (APHV) was estimated as the difference between chronological age and MO. The independent association of BMI and VJP with BP was further examined using binary logistics regression models. Separate analyses were conducted for girls and boys. Odd ratios (95%CI) of being hypertensive were calculated between BMI and VJP categories. The amount of variation in BP explained by the model was determined using the Cox and Snell R square and Nergelkerke R square [14]. Models were adjusted for MO as a potential confounding variable. The predictive capacities of the independent variables for the risk of BP were determined through the ROC analysis with 95% confidence intervals (95%CI). Threshold values for identifying risk of HTN were determined through area under curve (AUC) values, sensitivity, and specificity. A diagnostic test with AUC equal to 1 is perfectly accurate and another with a value of 0.5 has no discriminatory power. Tests with the AUC of 0.9–1.0 = highly accurate; 0.7–0.9 = moderate; and < 0.7 = less accurate [19]. All analyses were conducted using the statistical package for the social sciences (SPSS Version 20, IBM corporation, Armonk, NY, USA).

*Association of Fatness and Leg Power with Blood Pressure in Adolescents DOI: http://dx.doi.org/10.5772/intechopen.106279*
