Analysis of growth in a complex muscle (M. supracoracoideus, Anas platyrhynchos).

Volumetric growth of supracoracoideus muscles in domestic ducks from hatching to 10 weeks was divided into components due to longitudinal and radial (cross sectional area) growth. Although deceleration occurred in week 7, growth increments from both dimensions were still found in week 10. At the cellular level, deceleration of muscle fiber radial growth was later (week 9) than longitudinal fiber growth (week 7). By week 10, longitudinal fiber growth had ceased. Analysis of muscle geometry suggested that radial muscle fiber growth contributed to both whole muscle length and cross sectional area.