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F-29 Free Communication/Poster - Physical Activity and Public Health: Youth: MAY 29, 2009 1: 00 PM - 6: 00 PM ROOM: Hall 4F

Derivation Of Aerobic Fitness Cutpoints For Adolescents Using Reciever Operator Characteristic (ROC) Curve Analyses

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Board #129 May 29 3:30 PM - 5:00 PM

Welk, Gregory J. FACSM; Eisenmann, Joey C.; Laurson, Kelly R. FACSM

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Medicine & Science in Sports & Exercise: May 2009 - Volume 41 - Issue 5 - p 443-444
doi: 10.1249/01.MSS.0000355900.67072.7b
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Although it is widely acknowledged that aerobic fitness is important for the health of children and adolescents, there remains no universally accepted classification system. The criterion-referenced standards for aerobic fitness in FITNESSGRAM are widely accepted but these standards were developed using adult risk profiles extrapolated by age.

PURPOSE: The purpose of this study was to develop age- and gender-specific aerobic fitness standards in youth using receiver operator characteristic (ROC) curves - a graphical procedure that facilitates consideration of both specificity (Se) and sensitivity (Sp).

METHODS: We combined data for aerobic fitness, anthropometrics and metabolic syndrome variables of 8 to 18 year olds across 2 cross-sectional waves of NHANES (1999-2000 and 2001-2002). Age-, gender- and race-specific distributions of aerobic fitness were first developed using LMS statistical procedures to depict the nature of the growth-related distributions (i.e., centiles) for boys and girls. Z-scores derived from the LMS procedure were then used in the ROC analyses to derive the optimal threshold to define risk. The ROC analyses were conducted to determine the aerobic fitness levels that best discriminate between youth with or without metabolic syndrome (defined as having 3 or more risk factors based on age-modified cutpoints of the ATP III criteria).

RESULTS: The resulting ROC curves showed large values for area under the curve (AUC) in both boys (87.4) and girls (77.2). The optimal threshold value from the ROC plots yielded good diagnostic characteristics for both boys (Se=86.8%; Sp=82.9%) and girls (Se=90.1; Sp= 61.3%). In girls, the ROC derived health-related standards decline from 40 ml/kg/min to 38 ml/kg/min between 12 to 18 years old. In boys, values increase from approximately 44 ml/kg/min to 49 ml/kg/min. The ROC derived health-related standards are higher (∼2-5 ml/kg/min) than the current FITNESSGRAM values but the patterns were consistent.

CONCLUSIONS: The generally high AUC values and high Se/Sp values demonstrate that the aerobic fitness criteria have good utility for detecting risk of metabolic syndrome. A unique advantage of the proposed ROC-derived standards is that the sensitivity and specificity are equivalent across the entire adolescent age range.

© 2009 American College of Sports Medicine