Tera M. Hawes1, Santiago S. Umana1, Kelsey T. Minor1, Ashley A. Herda2, Elizabeth A. Holmes1, Christopher J. Cleary2, John P. Thyfault3,5, Robin P. Shook4,5, & Trent J. Herda1,5

1University of Kansas, Lawrence, Kansas; 2University of Kansas – Edwards Campus, Overland Park, Kansas; 3University of Kansas Medical Center, Kansas City, Kansas; 4Children’s Mercy Hospital, Kansas City, Missouri; 5Center for Children’s Healthy Lifestyle and Nutrition, Kansas City, Missouri

PURPOSE: The purpose of this study was to examine potential differences in muscle cross-sectional area (CSA) and thickness (MT) of vastus lateralis (VL) between prepubescent youth who were overweight/obese (OW/OB) versus normal weight (NW). In addition, this study examined the agreement between CSA and MT derived from magnetic resonance imaging (MRI) and ultrasound imaging (US). METHODS: Twenty-nine healthy, prepubescent subjects (15 males, 14 females, age=9.3±0.9 yrs, height=137.6±8.5 cm; body mass=34.8±9.6 kg) completed the study. Twenty-two of these subjects were classified as NW and eight subjects were classified as OW/OB. CSA and MT were measured for the VL with MRI and US. The MRI and US were performed on the VL at 40% distance between the lateral femoral epicondyle and the anterior superior iliac spine. The MRI and US CSA (cm2) and MT (cm) was calculated for each subject. T-tests and effect sizes (Cohen’s d) were calculated to examine potential differences in CSA and MT between OW/OB and NW for the US and MRI. In addition, correlations were performed to measure agreement for CSA and MT between the MRI and US. RESULTS: OW/OB had significantly greater US CSA (p<0.001; d=2.00) and MT (p<0.001; d=1.68) and MRI CSA (p<0.001; d=1.56) and MT (p=0.001; d=1.39) than NW. In addition, there were significant correlations (p<0.001) between MRI and US for CSA (R2=0.89) and MT (R2=0.75). CONCLUSION: Prepubescent OW/OB youth possessed larger VLs in this sample, which may be due to chronic overload. The effect sizes would suggest that there were greater magnitudes of difference between CSA and MT for the US in comparison to MRI. In addition, there was better agreement for CSA from the MRI and US in comparison to MT. Overall, the US compares favorably to the MRI CSA and MT measurements and could potentially be more sensitive to differences between the groups.

ACKNOWLEDGEMENTS: This study was funded by the National Strength and Conditioning Association Foundation.

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