6.1 Wednesday, Jan. 4 Measuring muscle pennation in vivo using sonomicrometry and 3-D X-ray cinematography methods. DE BOEF MIARA, M.*; BIEWENER, A.A.; Concord Field Station, Harvard Univ., Cambridge, MA; Concord Field Station, Harvard Univ., Cambridge, MA firstname.lastname@example.org
In vivo muscle performance is dependent on many anatomical and physiological factors including muscle fiber type, force-length properties and architectural organization. Many of these factors are fixed or change very slowly and thus in situ or post-mortem measures can be used for in vivo analyses. In contrast, a few factors may change so quickly that direct in vivo measures are desirable. In this study one such component of muscle architecture, pennation angle, was observed in vivo in the medial and lateral gastrocnemius of Helmeted Guineafowl (Numida meleagris). This was done in two ways. First, a triad of sonomicrometry crystals simultaneously measured muscle depth and muscle fascicle length. Assuming these measures formed two sides of a right triangle, trigonometry was used to calculate pennation angle. Later, these same crystals were observed using 3-D x-ray cinematography allowing for a direct measure of pennation. In both muscles a characteristic pattern of change in muscle pennation was observed during each stride with pennation angle decreasing during stance and increasing during swing. These patterns were exaggerated as locomotor speed and muscle force increased. A comparison of the two methods revealed that while 3-D cinematography is more accurate, with good crystal placement, sonomicrometry alone can give consistent results.