Meeting Abstract

P1.148  Monday, Jan. 4  Effects of muscle pennation on its kinematics and force development RAHEMI, H; NIGAM, N; WAKELING, JM*; Simon Fraser University, Burnaby, BC hrahemi@sfu.ca

Force development, power production and mechanical efficiency of muscle fibers depend on the speed at which they shorten. In a pennate muscle, individual fibers are aligned with a pennation angle relative to the line of action of the muscle belly. Pennate muscles have typically been associated with high force production because of higher number of fibers they consist. Recent work indicates that rotations of fibers can change their gearing and mechanical effectiveness in case of controlling muscle force output and velocity simultaneously. Here we have modeled the role of pennation on the fiber length and force production of whole muscle. Muscle fibers had physiologic tension-length properties (passive and active), muscle bellies were assumed to maintain constant volume, and tendon and aponeurosis compliances was included. Muscles with greater initial pennation had lower gearing (muscle belly strain: fibre strain) and greater fiber rotations. Muscles with lower initial pennation developed greater force than would have been predicted from their resting physiological cross-sectional area and pennation alone. Whilst pennation does lead to increased muscle force, this is not its only role. When muscles contract their internal architecture changes and this may be utilized to maintain optimal gearing between the fibers and muscle belly. Muscle pennation alters the way the internal architecture changes during contractions.