Association between 9-minute walk/run test and obesity among children and adolescents: evidence for criterion-referenced cut-points – article summary
Title: Association between 9-minute walk/run test and obesity among children and adolescents: evidence for criterion-referenced cut-points.
Authors: Diego Augusto Santos Silva, Justin J. Lang, Edio L. Petroski, Julio B. Mello, Adroaldo C.A Gaya and Mark S. Tremblay
Monitoring aerobic fitness in the pediatric population is an important metric used to estimate overall health in children. Field-based tests, such as the 9-minute walk/run test, have been regularly used to measure the aerobic capacity of children as these tests have been previously determined reflect physical fitness levels. However, the literature describes a variety of definitions for appropriate cut-point to distinguish healthy and unhealthy aerobic fitness capacities. These inconsistencies pose a challenge for those evaluating aerobic fitness in children. Past studies have demonstrated that obesity in children is inversely related to aerobic fitness capacity. Therefore, the authors of this study sought to define an appropriate criterion-referenced cut-point in children and adolescence for the 9-minute walk/run test based on the presence of obesity. Additionally, the authors aimed to determine if there was an association between a child’s performance on the 9-minute walk/run test and obesity.
A total of 61,465 children (53.4% males and 45.7% females) ages 6-17 years (mean age 11.2) were recruited purposefully by a non-randomized sampling via a project called the “Brazil Sports” Project (PROESP-BR). This project was conducted as a repeated cross-sectional surveillance study between the years of 1999-2015. It was designed to evaluate the physical fitness levels of children and adolescents across Brazil. Participants were included in the study as long as maximal effort exercise was not contraindicated by any medical conditions.
Physical Education teachers across Brazil were trained on the testing protocol and then administered the 9-minute walk/run test. Participants were instructed to run as far as they could in 9 minutes, and were allowed to walk if needed. The BMI of each participant was also calculated using their height and weight in order to categorize those with obesity, which was defined as being greater than +2 standard deviations from the mean.
The authors used Pearson’s correlation coefficient to determine the relationship between obesity and physical performance in the walk/run test. Furthermore, the researchers calculated the receiver-operating characteristics (ROC), which was quantified by the area under the curve (AUC) of the plotted data. This was used to assess whether physical performance in the walk/run test would, in fact, be predictive of obesity.
The researchers found that across all ages and in both sexes, there was a negative correlation between the physical performance in the 9-minute walk/run test and obesity. Furthermore, after analyzing the AUCs, it was determined that the distance the participant completed during the test was sufficient to predict obesity in all ages. The cut-points for obesity in boys were found as follows: 1,200m for ages 6-8 years, 1,300m for ages 9-11 years, 1,380m for ages 12-14 years, and 1,520m for ages 15-17 years. For girls, the cut-points were found to be as follows: 1,070m for ages 6-8 years, 1,160m for ages 9-11 years, and 1,200m for 12-17 years.
The current study had the benefit of analyzing a very large sample size of children and adolescents, which strengthened the significance of the results. The wide age range was also a strength of the current study. However, as the children were recruited from schools participating in the PROESP-BR program, the sample is not as generalizable compared to a randomized sample population. Moreover, using a high BMI as a determination of obesity is less reflective of true body composition in a youth population as they are still growing and developing.
Overall, the cut-points proposed by the current study were predictive of obesity in children and adolescents. This information could potentially be implemented as a guide for future proctors utilizing the 9-minute walk/run test. However, as the authors indicated, this study was the first of its kind to propose specific cut-points in regard to obesity. As this is the case, more research must be conducted to further validate the results.