Changes in human muscle architecture in disuse-atrophy evaluated by ultrasound imaging.

The aim of this study was to investigate if changes in muscle architecture occurred as a result of disuse-atrophy. Anatomical cross-sectional area (ACSA), muscle volume (V), fibre length (Lf) and pennation angle (theta) of the gastrocnemius medialis (GM) were evaluated by MRI and real-time ultrasound in 8 male patients with unilateral lower limb atrophy. The architectural data of the injured (I) and uninjured (UN) legs were compared. Values are means +/- S.E.M. The GM ACSA was 23.1 +/- 2.8% smaller in the I leg (P<0.001). Both theta and Lf of the I leg GM were respectively smaller by 16.42 +/- 2.9% (P<0.001) and 12.7 +/- 1.9% (P<0.001) than of the UN leg GM. The decrease of GM ACSA was highly correlated (P<0.001, R2=0.925) with the decrease in theta. It is concluded that disuse muscle atrophy leads to significant changes in muscle architecture.