Background: Computed tomography (CT) images at L4-L5, T12-L1 and the midthigh are commonly used to assess abdominal adiposity, liver fat, and muscle quantity (mass) and quality (lipid), respectively. Unknown is whether abdominal skeletal muscle (SM) at L4-L5 or T12-L1 can also be used to reflect thigh SM quantity and quality, which is often considered the criterion measure. Also unclear is whether changes in thigh SM quantity and quality are reflected by corresponding changes in abdominal SM quantity and quality.
Purpose: We examined the associations between abdominal SM and thigh SM quantity and quality in overweight/obese postmenopausal women before (n = 125) and after (n = 86) a 6-month exercise intervention trial.
Methods: CT was used to assess muscle quantity and quality at the midthigh, L4-L5, and T12-L1.
Results: At baseline, abdominal SM quality was significantly associated with thigh SM quality at L4-L5 and T12-L1 (R2 = 0.22 and R2 = 0.37, respectively; P < 0.01). Similarly, at baseline, abdominal SM quantity and quality was significantly associated with thigh SM quantity at L4-L5 and T12-L1 (R2 = 0.37 and R2 = 0.48, respectively; P < 0.01). Changes in thigh SM mass were marginally associated with changes in abdominal SM at T12-L1 (R2 = 0.08, P = 0.01) but not at L4-L5 (P > 0.10). Changes in thigh SM quality were associated with corresponding changes in abdominal SM quality at both L4-L5 and T12-L1 (R2 = 0.43 and R2 = 0.73, respectively).
Conclusions: Measurements obtained from a single CT image taken within the abdomen are moderately correlated with measures of thigh SM quantity and quality at baseline. Changes in thigh SM mass are poorly tracked by changes in abdominal SM. However, abdominal SM does provide comparable measures of muscle quality change.