research interests: Spinal neuromotor control and biomechanics of lower/hind- limb movement.
Ph. D., Skeletal Muscle Regeneration, University of Bristol 1975
My general interest is in how mammalian movement is accomplished, from the overall limb biomechanics to the neural coordination of muscles and the structural details of muscle which transmit sarcomere activity into the forces and displacements that underly every movement. An additional interest is how altered environments such as in spaceflight and pathologies, such as atrophy impact the normal execution of movement. Most recent work has been in collaboration with Dr. Shantanu Sinha in the Department of Radiology at UCSD (http://radiology.ucsd.edu/about-us/people/faculty/shantanu-sinha) and with Professor J.S. Chen in the Department of Civil Engineering at UCLA (http://www.cee.ucla.edu/faculty/chen/profile). We are investigating how intramuscular structure impacts whole muscle force and displacement. MRI imaging is used to provide muscle structure data and also a pixel-resolution map of intramuscular displacements. Finite element computational models of 'generic' muscles have been used to simulate muscle contractions and the intramuscular deformations compared with experimental observations. These efforts indicate that intramuscular morphology, such as fiber pennation angle and elastic properties of intramuscular passive materials have a significant impact on muscle performance. Furthermore, our results suggest specific properties of intramuscular passive materials which will be investigated in the future. We are currently developing a database of subject-specific muscle morphologies using several MRI techniques to image intramuscular fat, connective tissue, muscle fiber pennation angles and intramuscular dynamics of muscle contractions. Parallel efforts are being made to convert the data into subject-specific, image-based computational models in which simulated contractions can be compared with observations of real muscles contracting. Previously document variability in muscle structure will allow us to determine the impact of intramuscular structure on muscle performance. An additional interest is in the degree to which the changes in structure wrought by muscle atrophy contribute to the disproportionate loss of function relative to the loss of muscle mass or cross sectional area. We hope to approach this by conducting studies on muscles before, after and during recovery from atrophy artificially induced by muscle disuse.
Sinha S, Shin DD, Hodgson JA, Kinugasa R, Edgerton VR, "Computer-controlled, MR-compatible foot-pedal device to study dynamics of the muscle tendon complex under isometric, concentric, and eccentric contractions", J Magn Reson Imaging, 36 (2): 498-504 (2012) .
Hodgson JA, Chi SW, Yang JP, Chen JS, Edgerton VR, Sinha S, "Finite element modeling of passive material influence on the deformation and force output of skeletal muscle", J Mech Behav Biomed Mater, 9 : 163-183 (2012) .
Kinugasa R, Hodgson JA, Edgerton VR, Sinha S, "Asymmetric deformation of contracting human gastrocnemius muscle", J Appl Physiol, 112 (3): 463-470 (2012) .
Sinha U, Sinha S, Hodgson JA, Edgerton VR, "Human soleus muscle architecture at different ankle joint angles from magnetic resonance diffusion tensor imaging", J Appl Physiol, 110 (3): 807-819 (2011) .
Kinugasa R, Hodgson JA, Edgerton VR, Shin DD, Sinha S, "Reduction in tendon elasticity from unloading is unrelated to its hypertrophy", J Appl Physiol, 109 (3): 870-877 (2010) .
Chi SW, Hodgson J, Chen JS, Reggie Edgerton V, Shin DD, Roiz RA, Sinha S, "Finite element modeling reveals complex strain mechanics in the aponeuroses of contracting skeletal muscle", J Biomech, 43 (7): 1243-1250 (2010) .
Shin DD, Hodgson JA, Edgerton VR, Sinha S, "In vivo intramuscular fascicle-aponeuroses dynamics of the human medial gastrocnemius during plantarflexion and dorsiflexion of the foot", J Appl Physiol, 107 (4): 1276-1284 (2009) .
Shin D, Finni T, Ahn S, Hodgson JA, Lee HD, Edgerton VR, Sinha S, "Effect of chronic unloading and rehabilitation on human Achilles tendon properties: a velocity-encoded phase-contrast MRI study", J Appl Physiol, 105 (4): 1179-1186 (2008) .
Kinugasa R, Shin D, Yamauchi J, Mishra C, Hodgson JA, Edgerton VR, Sinha S, "Phase-contrast MRI reveals mechanical behavior of superficial and deep aponeuroses in human medial gastrocnemius during isometric contraction", J Appl Physiol, 105 (4): 1312-1320 (2008) .
Shin D, Finni T, Ahn S, Hodgson JA, Lee HD, Edgerton VR, Sinha S, "In vivo estimation and repeatability of force-length relationship and stiffness of the human achilles tendon using phase contrast MRI", J Magn Reson Imaging, 28 (4): 1039-1045 (2008) .