Objectives: To describe muscle size and architecture of the gastrocnemius medialis (GM) muscle in eleven adult males with
Duchenne Muscular Dystrophy (DMD, age 24.5±5.4 years), and a control group of eleven males without DMD (CTRL, age
22.1±0.9 years). Methods: GM anatomical cross sectional area (ACSA), volume (VOL), physiological cross sectional area
(PCSA), fascicle length (Lf) and pennation angle (θ) were assessed using B-Mode Ultrasonography. GM ACSA was measured
at 25, 50 and 75% of muscle length (Lm), from which VOL was calculated. At 50% of Lm, sagittal plane images were analysed
to determine GM Lf and θ. GM PCSA was calculated as: VOL/Lf. The ratio of Lf and Lm was also calculated. Results: GM
ACSA at 50% Lm, VOL and PCSA were smaller in DMD males compared to CTRL males by 36, 47 and 43%, respectively
(P<0.01). There were no differences in Lf and θ. GM Lm was 29% shorter in DMD compared to CTRL. Lf/Lm was 29% longer
in DMD (P<0.01). Conclusions: Unlike previous data in children with DMD, our results show significant atrophy in adult males
with DMD, and no change in Lf or θ. The shorter Lm may have implications for joint flexibility
