Differences Between Principal Strain Directions and Muscle Fiber Directions in the Contracting Biceps Bracii Measured With CPC-MRI

Skeletal muscle exhibit non-uniform internal architectures and our research goals are to relate these to their internal mechanics during contraction to provide a better understanding of muscle function, verify muscle models and permit more sophisticated interpretation of the functional effects of injury. Our previous studies have developed a novel method to calculate 2D Lagrangian strain field of skeletal muscle from the CPC-MRI [1]. The objective of this study is to apply CPC-MRI to derive Lagrangian strain fields for the normal biceps brachii and to determine its minimum principal strain directions in vivo during contraction. We will then compare them to the muscle fiber directions or pennation angles measured by a parallel ultrasound study. If we assume the muscle force is mainly transmitted along fiber directions, we would expect that the minimum principal strain directions are the same as fiber directions. Comparisons between different regions of the muscle and flexion angles will also be made.