Ultrasound most reliable for muscle thickness measurement at ventral thigh, anterior upper arm

When using ultrasound to assess muscle thickness, measuring at the ventral point on the thigh and the anterior point on the upper arm yields high reliability.

“We recommend measuring adipose tissue and muscle thickness at the ventral measuring point of the thigh and the anterior measuring point of the upper arm,” the researchers said.

The study included five examiners who each performed 20 ultrasound scans in 120 healthy participants. Ultrasound measurements were performed at two marking points on the upper limb (anterior and anterolateral) and three on the thigh (medial, ventral, and lateral). The outcomes of interest were intra- and inter-examiner reliability in marking the measuring points and in measuring adipose and muscle thickness.

Of the 3,600 planned scans, 3,552 (98.7 percent) were successfully performed, of which 86.6 percent (n=3,118) were deemed to be of best quality. This was particularly true for measurements collected at the anterior point of the upper arm and ventral point of the thigh, 95 percent of which were deemed to be of the best quality.

Reliability of measurements for upper arm and thigh lengths ranged from high to very high and in both cases, inter-examiner reliability tended to be lower. Inter- and intra-examiner reliability was likewise high for adipose tissue thickness across all measuring points.

In contrast, muscle thickness measurements collected at the lateral and medial thigh, as well as at the anterolateral point of the upper arm, showed low reliability, with coefficients below 0.65. Only thickness measurements collected at the ventral thigh and anterior upper arm had high to very high reliability coefficients.