Development of Nomogram to Predict the Best Military Category Using Physical Fitness Variables: A Model Development in Navy Trainees

Background: Physical readiness plays an important role in a navy student’s life. Objectives: The current study aimed at building a valid and accurate statistical model using the physical readiness variables to predict the best military category for the students of the NEDAJA and putting the complex concepts of this model to a practical tool such as nomogram. Methods: The current cross sectional study included all the navy students (Islamic Republic of Iran Navy) studying from 2011 to 2012 in the Imam Khomeini Naval University of Noshahr. Out of 733 students in the university, 260 were randomly selected and measured in terms of physical readiness variables. The number of subjects in each group was calculated using binary logistic regression. The Stata/MP ‘nomolog’ command was used to develop nomogram after building the finalized model by logit prediction command (binary logistic regression model). Results: The mean age of the subjects was 21.2 ± 2.1 years; 59 out of 171 participants (34.5%) in navigation, 78 (45.6%) in marine, 26 (15.2%) in sea scouts, 50 (29.2%) in electronics, and 59 (34.5%) in mechanics categories met the inclusion criteria. The nomogram was developed according to the inclusion criteria for each model. After matching the values of independent variables by the appropriate score, the probability, which responds to the total points, is figured out. The benefit of a nomogram maps the measure of associations into easy scores on a scale from 0 to 100 in a user-friendly figure. The total points collected by the various independent variables correspond to the predicted probability for a student. Conclusions: A nomogram was developed to predict the best military category for the Iranian navy students, using the variables from the physical readiness. It showed excellent discriminating and predicting ability with high accuracy. To the authors’ best knowledge it was the first paper that developed nomogram to be used in military medicine. Keywords: Nomogram; Logistic Regression; Physical Fitness