# Predictive Modeling of VO2 max Based on 20 m Shuttle Run Test for Young Healthy People
## 2 Material and Methods  
### Participants  
The nature of the study was cross-sectional. It applied to a group of 1097 (aged 19.7 \(\pm\) 1.4) healthy students (487 males aged 20.0 \(\pm\) 1.6 and 610 females aged 19.5 \(\pm\) 1.3) studying in five large academic centres in Poland (Krosno State College, University of Rzeszow, Maria Curie Sklodowska University in Lublin, Cracow University of Technology and Poznani University of Life Sciences). The study group was selected in two stages. In the first stage, randomly selected students at the academic level of bachelor's studies participated in a 20 m SRT. Based on the median of the covered distance (sections): Me = 880 m for females (44 sections) and Me = 1520 m for males (76 sections) people who completed 20 m SRT below and above the median of the distance covered (sections) were selected for the second stage to ensure the highest possible differentiation of results. Finally, 154 women (aged 20.3 \(\pm\) 1.2) and 154 men (aged 20.8 \(\pm\) 1.8) participated in the last stage. They participated in a 20 m SRT and the VO2 max was identified using a portable gas analyser K4b2. Before the cardiac stress test, a skilled study team made anthropometric measurements. The body height was measured with a stadiometer (SECA 213 Hamburg, Germany) with an accuracy of up to 1 mm. Measurements of the waist circumference were carried out with non-elastic flexible tape according to two protocols: WHO (World Health Organization) STEPS protocol (approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest) and according to US NIH (United States National Institutes of Health) protocol (a measurement was made at the top of the iliac crest) [37]. The hip circumference measured around the widest portion of the buttocks. The body weight and body weight components (Fat--body fat percentage, FFM--fat free mass, TBW--total body water) were measured by means of Body Composition Analyzer Tanita TBF 300 (Tokyo, Japan). Table 1 presents used somatic indexes with equations. Generally, the measured anthropometric parameters (height and body weight, waist circumference, WHR--waist-hip ratio, WHtR--waist to height ratio, BMI--body mass index, BAI--body adiposity index) comply with the results for the mean values of the parameters in the population of Polish students presented in studies by other authors [38; 39].  
A description of the variables (e.g., VO2 max level, age, heart rate and anthropometric parameters) together with the basic statistics (mean value and standard deviation) is given in Table 2. The models were calculated on the basis of 23 independent variables (\(x_{0}\)-\(x_{22}\)) and one dependent variable (\(y\)). Independent variables include: gender (\(x_{1}\)), parameters of the 20 m shuttle run (\(x_{1}\)-\(x_{4}\)),age (\(x_{5}\)), anthropometric features (\(x_{6}\)-\(x_{10}\)), somatic indexes (\(x_{11}\)-\(x_{19}\)), and body components (\(x_{20}\)-\(x_{22}\)). The VO2 max result (\(y\)) obtained during the 20 m shuttle run test with a telemetry gas exchange system (Cosmed K4b2) was a dependent variable.