Influence of structure on the tissue dynamics of the human soleus muscle observed in MRI studies during isometric contractions.

This article investigates how the internal structure of muscle and its relationship with tendon and even skeletal structures influence the translation of muscle fiber contractions into movement of a limb. Reconstructions of the anatomy of the human soleus muscle from the Visible Human Dataset (available from the National Library of Medicine), magnetic resonance images (MRI), and cadaver studies revealed a complex 3D connective tissue structure populated with pennate muscle fibers. The posterior aponeurosis and the median septum of the soleus form the insertion of the muscle and are continuous with the Achilles tendon.

Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study.

The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry.

Muscle synergism during isometric plantarflexion in achilles tendon rupture patients and in normal subjects revealed by velocity-encoded cine phase-contrast MRI.

Background: The triceps surae muscle is often considered to be the sole contributor to the plantarflexion torque although the deeper plantarflexor muscles may also be activated in the plantarflexion task.

Methods: We measured coordinative strategies and muscle synergism during isometric plantarflexion task from 11 volunteers. Velocities from the distal end of the medial gastrocnemius, soleus, and flexor hallucis longus muscles were encoded in the superior-inferior direction using cine phase-contrast magnetic resonance imaging.

Muscle kinematics during isometric contraction: development of phase contrast and spin tag techniques to study healthy and atrophied muscles.

Purpose: To develop and compare phase-contrast (PC) and spin-tag (ST) MR imaging techniques for accurate quantification of velocity and displacement distribution in the muscle tendon complex of the lower leg during isometric contractions under in vivo conditions, in healthy subjects and subjects with atrophy.

Materials And Methods: Techniques were developed to acquire PC and ST dynamic images, gated to the force exerted by a subject during isometric contraction. Algorithms were optimized for correction of phase shading errors.

Mapping of movement in the isometrically contracting human soleus muscle reveals details of its structural and functional complexity.

It is becoming increasingly apparent that precise knowledge of the anatomic features of muscle, aponeurosis, and tendons is necessary for understanding how a muscle-tendon complex generates force and accomplishes length changes. This report presents both anatomic and functional data from the human soleus muscle acquired by using magnetic resonance imaging. The results show a strong relationship between the complex three-dimensional structure of the muscle-tendon system and the intramuscular distribution of tissue velocities during in vivo isometric contractions.

Nonuniform strain of human soleus aponeurosis-tendon complex during submaximal voluntary contractions in vivo.

The distribution of strain along the soleus aponeurosis tendon was examined during voluntary contractions in vivo. Eight subjects performed cyclic isometric contractions (20 and 40% of maximal voluntary contraction). Displacement and strain in the apparent Achilles tendon and in the aponeurosis were calculated from cine phase-contrast magnetic resonance images acquired with a field of view of 32 cm.