# Predictive Modeling of VO2 max Based on 20 m Shuttle Run Test for Young Healthy People
## 4 Discussion
The model determined for males consisted of the following variables: distance (20 m SRT) (\(x_{1}\)), waist circumference (NIH protocol) (\(x_{9}\)), WHR (NIH protocol) (\(x_{14}\)), FFMI (\(x_{17}\)) and BSA (\(x_{19}\)). The obtained collection of predicators is not incidental and the significance of each variance for VO\({}_{2}\)max is reflected in the literature. Waist circumference and WHR are popular indicators used for the evaluation of cardiovascular diseases [71]. Waist circumference is also a predictor of visceral fat and indicator of central obesity [72]. There remains no uniformly accepted measurement protocol, resulting in a variety of techniques employed throughout the published literature [73; 74]. The most commonly used are four measurements of waist circumference defined by specific anatomic landmarks: (1) immediately below the lowest ribs, (2) at the narrowest waist, (3) the midpoint between the lowest rib and iliac crest, and (4) immediately above the iliac crest [75; 76]. Measurements made at the umbilicus are also commonly used in clinical and research settings [74]. Besides DXA and bioimpedance, different indicators based on anthropometric measurements are used for the evaluation of body fat content. The indicator that is often used in obesity studies is BMI [39; 71; 77]. However, it presents some limitations. It neither evaluates the content of adipose tissue and its distribution in the body nor does it differentiate body fat content depending on age, sex and ethnic origin [71; 78]. The identification of adipose tissue location is necessary to detect visceral (central) obesity, which increases the risk of cardiovascular diseases [79]. That is why the qualitative supplementation of the classical concept of BMI may help to create reference values for FFMI for a given age category [80]. BSA, a method for describing body size, is commonly used in medicine as a biometric unit [81; 82]. The use of a predictive model makes it possible to determine the level of CFR without using expensive equipment and specialized research teams. The prediction of the VO2 max parameter may be useful as an element of monitoring the health and physical performance of students of young healthy people. The strongest points of presented paper are:  
* a large research group representing the population,
* VO2 max measurements made using direct methods,
* the use of a large set of variables to determine the optimal predictors for VO2 max estimation,
* and obtaining a relatively small VO2 max estimation error. The limitations of the study are related to the using models in practice. VO2 max estimation by the proposed models should be performed for healthy people of the same age as the research group. **Author Contributions:** Conceptualization, K.P., Z.B., E.N.-B. and E.Z. ; Data Curation, Z.B., M.Z.-D. and K.S. ; Formal Analysis, K.P. and K.H.P. ; Funding Acquisition, E.N.-B. ; Investigation, Z.B., M.Z.-D., E.N.-B., M.H., K.S. and E.Z. ; Methodology, K.P., Z.B., K.H.P. and E.Z. ; Project Administration, E.N.-B. and M.H. ; Software, K.P. and B.D. ; Supervision, E.Z. ; Writing--Original Draft, K.P., Z.B., M.Z.-D., K.H.P. and E.Z. ; Writing--Review and Editing, K.P., M.Z.-D. and E.Z. **Funding:** This work has been supported by the Polish Ministry of Science and Higher Education within the research project \"Development of Academic Sport\" in the years 2016-2019, project No. N RSA4 01654  
**Conflicts of Interest:** The authors declare no conflict of interests. **Ethical Standards:** Written informed consent was obtained from all subjects. The project and used methods were approved by the Bioethics Committee of Rzeszow University, Poland, which noted the absence of any contraindications and ethical violations (Resolution No. 20/12/2015). The research was conducted according to the guidelines laid down in the Declaration of Helsinki.