RT Journal Article
SR Electronic
T1 Muscle structure governs joint function: linking natural variation in medial gastrocnemius structure with isokinetic plantar flexor function
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 547042
DO 10.1101/547042
A1 John F. Drazan
A1 Todd J. Hullfish
A1 Josh R. Baxter
YR 2019
UL http://biorxiv.org/content/early/2019/07/10/547042.abstract
AB Generating ankle torque is critical for locomotion in elite athletes, the elderly, and many patient populations. Despite the robust findings linking plantar flexor muscle structure to gross function within these populations, the link between variation in plantar flexor fascicle length and ankle kinetics in healthy adults has not been established in the literature. In this study, we determined the relationship between medial gastrocnemius structure and peak torque and total work produced by the plantar flexors during maximal effort contractions. We measured resting fascicle length and pennation angle of the medial gastrocnemius using ultrasound in healthy adult subjects (N=12). Subjects performed maximal effort isometric and isokinetic contractions on a dynamometer. We found that longer fascicles were positively correlated with higher peak torque and total work (R2 > 0.41, p < 0.013) across all isokinetic velocities, ranging from slow (30 degrees per second) to fast (210 degrees per second) contractions. Higher pennation angles were negatively correlated with peak torque and total work (R2 > 0.296, p < 0.067). None of these correlations were significant in isometric conditions. To further investigate the coupled effect of fascicle length and pennation angle variation, we used a simple computational model to simulate isokinetic contractions. These simulations confirmed that longer fascicle lengths generate more joint torque and work throughout a greater range of motion. This study provides experimental and computational evidence that links plantar flexor muscle structure and ankle kinetics in healthy young adults, which lends new insight into locomotor function in a range of subpopulations. adults which provides insight into patient recovery following Achilles tendon rupture.