The Impact of Body Mass Index

Measurement Agreement Between Estimates of Aerobic Fitness in Youth: The Impact of Body Mass Index

Pedro F. Saint-Maurice, Gregory J. Welk, Kelly R. Laurson and Dale D. Brown

Research Quarterly for Exercise and Sport 85(1): 59=

Despite the potential for body mass and/or body composition to have an adverse effect on endurance test performance, there remains a lack of timely and relevant research in the exercise science field that warrants additional, systematic study. While it is known that Progressive Aerobic Cardiorespiratory Endurance Run (PACER) equations and the Mile Run Test are reliable and valid, recent health-related Fitnessgram standards were introduced in an effort to improve the usefulness of these measures for school assessment applications.

Therefore, the purpose of this exploratory study was to evaluate the effects of body mass index (BMI) on the congruence between the aerobic capacity estimates derived from the application of the Progressive Aerobic Cardiorespiratory Endurance Run (PACER) equations and the Mile Run Test. Based on the exploratory design of the study, Saint-Maurice et al.'s guiding hypothesis was that BMI has a major influence on aerobic fitness estimates. Drawing on previously collected data from 911 male participants and 755 female youths (grades 3-12) from four schools (two private and two public schools in a small town in the Midwestern United States based on their completion of the PACER and Mile using a counterbalanced design to identify congruence levels.

The results of this study showed that "BMI does have a major influence on aerobic fitness estimates from the PACER test" and "BMI explains 34% (11- to 14-year-olds) and 30% (15- to 18-year-olds) of the variance associated with differences among estimates from the Mile run and the PACER equations" (Saunt-Maurice et al. 61). These findings are important for school assessments of fitness-testing regimens. For instance, according to Saint-Maurice et al., "This is an important issue for school-based fitness-testing programs such as Fitnessgram because the goal is to provide accurate indicators of health-related fitness for both individual- and school-level reports" (59).

This study helped to fill in a gap in the existing body of knowledge concerning the impact of BMI on fitness evaluation and classification agreement. To their credit, Saint-Maurice and his associates concede there were several limitations to their research that restrict its generalizability, but emphasize that they also took careful steps in their data analysis to minimize errors and the introduction of researcher bias. This study is not casual reading for exercise science professionals, but it does provide a useful background concerning the use of the PACER and Mile assessments and the importance of taking BMI into account when calculating the results that emerge from the administration of these performance tests.