Article

The free Achilles tendon (AT) consists of distinct fascicles arising from each of
the triceps surae muscles that may give rise to non-uniform behavior during
functional tasks such as walking. Here, we estimated in vivo deformations of the
human AT during walking using simultaneous ultrasound and motion capture
measurements. Ten subjects walked at three speeds (0.75, 1.00, and 1.25 m/s) on a
force-measuring treadmill. A custom orthotic secured a linear array transducer in
two locations: (1) the distal lateral gastrocnemius muscle-tendon junction and
(2) the free AT, on average centered 6 cm superior to calcaneal insertion. We
used motion capture to record lower extremity kinematics and the position and
orientation of the ultrasound transducer. A 2D ultrasound elastography algorithm
tracked superficial and deep tissue displacements within the free AT. We
estimated AT elongation (i.e., change in length) relative to the calcaneal
insertion by transforming the orthotic, transducer, and calcaneus kinematics into
a common reference frame. Superficial and deep regions of the free AT underwent
significantly different longitudinal displacements and elongations during
walking. For example, we found that the superficial AT exhibited 16-29% greater
peak elongation than the deep AT during the stance phase of walking (p < 0.01).
Moreover, superficial-deep AT tissue deformations became less uniform with faster
walking speed (p < 0.01). Non-uniform deformations of the free AT, which could
reflect inter-fascicle sliding, may enable the gastrocnemius and soleus muscles
to transmit their forces independently while allowing unique kinematic behavior
at the muscle fiber level.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS