Cross-sectional area of the thigh muscle in man measured by computed tomography

Nine subjects with different training background were studied by means of muscle biopsy from musculus vastus lateralis. The cross-cut area of the different muscle fibre types was measured. By the use of a soft tissue X-ray technique, computed tomography, a cross-sectional picture of the thigh was produced at the same level as the biopsy was taken. The total cross-cut area of the vastus lateralis muscle was measured from this picture. This technique to measure a cross-cut muscle area from an X-ray picture was evaluated and found to be accurate and reproducible. The mean fibre area was highly correlated (r = 0.91; P less than 0.001) to the cross-cut area of the vastus lateralis muscle. The total number of fibres in the vastus lateralis muscle was estimated. It was concluded that the cross-sectional area of the thigh muscle can be accurately determined by means of computed tomography. The larger cross-sectional area of the vastus lateralis muscle in well trained subjects was primarily explained by a larger cross-sectional area of the fibre, while the total number of fibres in the vastus lateralis muscle seemed to be fairly equal among the subjects.