Post-immobilization eccentric training promotes greater hypertrophic and angiogenic responses than passive stretching in muscles of weanling rats.

This study investigated how different types of remobilization after hind limb immobilization, eccentric exercise and passive static stretching, influenced the adaptive responses of muscles with similar function and fascicle size, but differing in their contractile characteristics. Female Wistar weanling rats (21 days old) were divided into 8 groups: immobilized for 10 days, maintaining the ankle in maximum plantar flexion; immobilized and submitted to eccentric training for 10 or 21 days on a declining treadmill for 40min; immobilized and submitted to passive stretching for 10 or 21 days for 40min by maintaining the ankle in maximum dorsiflexion; control of immobilized; and control of 10 or 21 days. The soleus and plantaris muscles were analyzed using fiber distribution, lesser diameter, capillary/fiber ratio, and morphology.

Change in the contractile behavior of muscle fibers in subjects with primary muscle dysfunction.

The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders.

Effects of 40min of maintained stretch on the soleus and plantaris muscles of rats applied for different periods of time after hindlimb immobilization.

Stretching is frequently used in physiotherapy to minimize or even reverse the alterations that occur after muscle disuse. Alterations that occur after 10 and 21 days of maintained stretch in soleus and plantaris muscles post-disuse were evaluated in the present study in experimental rats. Thirty adult female Wistar rats were divided into seven groups: hindlimb immobilization for 10 days; immobilization and 10 days stretched; immobilized and 21 days stretched; three control groups consisting of animals of different ages and anesthetized group.

Characterization of fiber types in different muscles of the hindlimb in female weanling and adult Wistar rats.

We analyzed lesser diameter and distribution of fiber types in different skeletal muscles from female Wistar rats using a histoenzymology Myofibrillar Adenosine Tri-phosphatase (mATPase) method. Fragments from muscles were frozen and processed by mATPase in different pH. Adult and weanling rat soleus muscles presented a predominance of type I fibers and larger fiber diameters.