A model of the left ventricle which combines a spheroidal geometry with a spatial fiber angle distribution is presented. The mechanics of each muscle fiber is described by its passive stress-strain relationship, active stress-strain relationship, and an activation function (half a sinusoid) which represents the time-dependent degree of activation of the fiber. A stress-strain rate relationship ...

The triceps surae (TS) muscle-tendon unit is 1 of the most commonly injured in elite and recreational athletes, with a high prevalence in middle-aged adults. The performance of maximal numbers of unilateral heel raises is used to assess, train, and rehabilitate TS endurance and conventionally prescribed in 0° knee flexion (KF) for the gastrocnemius and 45° for the soleus (SOL). However, the ext...

Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. A total of eight elderly (E; 76 +/- 1 yr) and eight young (Y; 20 +/- 1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis ...

Fiber orientation across the left ventricular myocardial wall has been studied. Specimens were obtained from 18 dog hearts rapidly fixed in situ in systole, in diastole, and in dilated diastole. Fiber orientation was determined across the free wall at eight sites from a T-shaped specimen by measurements with light microscopy in serial paraffin sections. Results indicate: (1) The wall has a well...

The muscle fiber composition and cross-sectional area of muscle fiber types were investigated histochemically in the abdominal muscles (rectus abdominis muscle, obliquus externus abdominis muscle, obliquus internus abdominis muscle and transversus abdominis muscle) of three Japanese macaques (Macaca fuscata). Muscle fibers were classified into three fiber types (Type I, II A and II B) by myosin...

We studied the effect of treadmill exercise on muscle fibers in mice with experimental steroid myopathy. Frozen sections of the extensor digitorum longus (EDL) and soleus (SOL) muscles were stained with hematoxylin-eosin, and the muscle fiber diameters measured. In the EDL, muscle fiber diameters in the steroid groups decreased significantly compared with those in the control groups; moreover, ...

PURPOSE Previous work has suggested a major role of scleral biomechanics in the pathogenesis of glaucoma. Since fiber orientation in connective tissues is a key determinant of tissue biomechanics, experimental characterization of scleral fiber orientation is needed to fully understand scleral biomechanics. This is a report of baseline experimental measurements of fiber orientation in whole norm...

The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynami...

This study suggested a new method to estimate muscle fiber number of ADM (abductor digiti minimi) muscle using surface electromyogram and muscle modeling. For muscle fiber number estimation, this study detected SMUAP (single motor unit action potential) by inducing the voluntary contraction of ADM muscle with less than 1% MVC (maximum voluntary contraction). The muscle fiber number was estimate...

STUDY DESIGN Controlled laboratory study. OBJECTIVES To measure the architectural properties of rat supraspinatus muscle after a complete detachment of its distal tendon. METHODS Supraspinatus muscles were released from the left humerus of 29 Sprague-Dawley rats (mass, 400-450 g), and the animals were returned to cage activity for 2 weeks (n=12), 4 weeks (n=9), or 9 weeks (n=8), before euth...