An Evaluation of Physical Fitness and Accuracy of Resting Metabolic Rate Prediction Equations in Reserve Officers' Training Corps Cadets and Midshipmen
Authors:   , Kelley Rachel Catherine , Volpe Stella L. 
Published: July 2021

The Reserved Officers' Training Corps (ROTC) is a program in which college students receive scholarship funds as well as leadership and physical fitness training in exchange for committed military service. There is limited scientific research describing fitness attributes of ROTC cadets and midshipmen, and no study has previously reported resting metabolic rate (RMR) for this population. The results of this cross-sectional study established a physical fitness profile of ROTC cadets and midshipmen (n = 17, 24% female; age = 21.0 ± 1.2 years). The characteristics of the sample were the following: body mass index (BMI) = 24.6 ± 2.0 kilograms/meters² (kg/m²); waist circumference (WC) = 77.2 ± 8.1 centimeters (cm); % body fat = 18.2 ± 5.0%; maximal oxygen consumption (VO₂max) = 45.7 ± 4.5 milliliters/kilogram of body weight/minute (mL/kg/min); RMR = 1526 ± 159 kilocalories/day (kcal/day); daily energy intake = 1885 ± 373 kcal/day; and daily intake of fruits and vegetables = 2.9 ± 1.1 cups/day. Percent body fat was measured using bioelectric impedance analysis (BIA). Maximal oxygen consumption and RMR were analyzed using indirect calorimetry. Data on daily energy intake and daily consumption of fruits and vegetables were collected from Block 2005 Food Frequency Questionnaires. This study also evaluated the accuracy of seven RMR prediction equations. Defining RMR for an active person is a fundamental component to diet planning. RMR accounts for the majority of an individual's daily energy expenditure. Indirect calorimetry is the gold standard for RMR measurement, but it is not a practical option for many nutrition professionals. Therefore, prediction equations exist that incorporate more convenient measures, such as height and weight, to estimate RMR. The most frequently used prediction equations (Harris-Benedict, Mifflin-St. Jeor, Owen, and Schofield) and an equation previously validated in athletes (Cunningham) were compared to measured RMR values. This accuracy analysis involved paired t-tests, Pearson's correlation coefficients, Bland-Altman plots, and the percentage of individuals for each equation for whom RMR was predicted within the accepted error range (i.e., ± 10% of the measured RMR). The Owen Weight equation demonstrated the lowest bias (mean difference from measured RMR = + 55 ± 84 kcal/day) and highest accuracy rate (88.2%). The Cunningham equation exhibited the greatest bias (mean difference from measured RMR = + 287 ± 125 kcal/day) and lowest accuracy rate (23.5%). Finally, possible relationships between fitness characteristics and measured RMR were explored using Pearson's bivariate correlation coefficients. Body weight exhibited the strongest correlation with measured RMR (r = 0.854, p = 0.001). Additional partial correlations controlling for the effects of body weight were performed. Previously significant correlations between measured RMR and height, BMI, WC, and lean body mass were no longer significant after controlling for the effects of weight (p > 0.05). In general, ROTC cadets and midshipmen exhibited normal body weights, healthy body composition profiles, and above average aerobic fitness. Resting metabolic rate was overestimated by all RMR prediction equations (p < 0.05). Future research should consider exploring regression analysis, incorporating body weight and lean body mass as predictors, to develop a RMR prediction equation that is specific and accurate for this population.