Association Between Waist-to-Height Ratio and FITNESSGRAM® Aerobic Capacity Classification in Sixth-Grade Children

Abstract

FITNESSGRAM® has established criterion standards for aerobic capacity (AC) to assess cardiorespiratory function. Standards for body composition and body mass index (BMI) have also been established. Waist-to-Height ratio (WHtR) has been shown to be a strong indicator of aerobic fitness in youth. PURPOSE: The purpose of this study was to determine the association between WHtR and FITNESSGRAM® AC classification in sixth-grade children. METHODS: Subjects were 528 sixth-grade boys and girls, ages 11-13, who completed each of the FITNESSGRAM® test components as a part of their yearly physical education assessment. AC was determined from one-mile run/walk (1MRW) times, age, gender and BMI. In addition to height and weight, subjects were also measured for waist circumference. The percent of these students classified within the Healthy Fitness Zone (HFZ) were 46% for BMI, and 52% for AC. The percent of these students classified as High Risk were 43% for BMI, and 31% for AC. RESULTS: The correlation between WHtR and 1MRW was .41, and the correlation between BMI and 1MRW was .42. The correlation between WHtR and AC was .83, and the correlation between BMI and AC was .91. Receiver Operating Characteristic (ROC) analysis indicated that a WHtR of 0.45 represents the best cut-off score for classifying girls within the HFZ for AC, with 89% classified correctly, and AUC = .94. Also, a WHtR of 0.48 represents the best cut-off score for classifying boys within the HFZ for AC, with 93% classified correctly, and AUC = .96. For determining High Risk classification for AC, a WHtR of 0.51 represents the best cut-off score for classifying girls as High Risk for AC, with 91% classified correctly, and AUC = .98. Also, a WHtR of 0.55 represents the best cut-off score for classifying boys as High Risk for AC, with 92% classified correctly, and AUC = .97. CONCLUSIONS: As with BMI, WHtR is strongly associated with classification according to FITNESSGRAM® AC standards in sixth-grade children. These data suggest that a WHtR of .45 for girls and .48 for boys are the best criteria for HFZ classification for FITNESSGRAM® AC. Also, a WHtR of .51 for girls and .55 for boys are the best criteria for High Risk classification for FITNESSGRAM® AC. Interventions for reducing WHtR are important since children in the High Risk category are most likely to develop health problems as adults.