Ana Claudia Mattiello-Sverzut

Morphological effects of two protocols of passive stretch over the immobilized rat soleus muscle

This study evaluated two different stretching protocols employed during a period of hind‐limb immobilization in terms of their effects on muscle morphology. Quantitative data regarding the soleus muscle were obtained based on the clinical hypothesis that a high frequency of this exercise would improve the recovery of muscle structure. Twenty‐four male Wistar rats were divided into four groups (n = 6 each): the control group (C); the immobilized group, in which the left hind limb was immobilized in order to maintain the soleus muscle in a fully shortened position for 3 weeks (I); the ‘immobilized and stretched every 3 days’ group, in which the left hind limb was immobilized as in the immobilized group, but with the soleus muscle stretched every 3 days for 40 min (Ist3); and the ‘immobilized (as in the immobilized group) and stretched every 7 days’ group (ISt7). All soleus muscles were excised 21 days after the beginning of the experiment, and were processed for (1) haematoxylin and eosin and myosin ATPase to evaluate muscle morphology and cross‐sectional area and the proportions of the different fibre types, and (2) ultrastructural analysis. The cross‐sectional area was found to have decreased in all fibre types (I, II and C), mainly in ISt7, when compared with the C group and ISt3 group. The proportion of the different fibre types did not show statistical difference between groups. Light and electron microscopy examination revealed signs of cell degeneration that was more intense in the group immobilized and stretched three times a week. In conclusion, sessions of passive stretching applied to the soleus during immobilization induce muscle fibre injury, suggesting that this therapeutic tool should be applied carefully to disused muscles.

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. In the plantar muscle in adult rats, the type IIB fibers demonstrated greater lesser diameter while in the weanling animals, types I and IIB fibers were larger. The plantar muscle of animals of both ages was composed predominantly of the type IID fibers. The type IID fibers were observed in similar amounts in the lateral gastrocnemius and the medial gastrocnemius muscles. Type IIB fibers showed predominance and presented higher size in comparison with other types in the EDL muscle. The present study shows that data on fiber type distribution and fiber lesser diameter obtained in adult animals cannot always be applied to weanling animals of the same species. Using the mATPase, despite the difficult handling, is an important tool to determine the different characteristics of the specific fibers in the skeletal muscle tissue.

The effects of aging on biceps brachii muscle fibers: a morphometrical study from biopsies and autopsies

OBJECTIVES In order to study the morphology and size of muscle fibers, cross sections of biceps brachii samples from autopsies, up to 9 hours after death, and biopsies of 72 subjects were compared. The subjects aged 13 to 84 years in both sexes. METHODS The samples obtained from autopsies (n=47) were from subjects with sudden death, or who died after acute disease without evidence of neuromuscular involvement. The biopsies (n=25) were from patients with symptoms suggestive of inflammatory or metabolic myopathy, not confirmed morphologically. The lesser diameter of muscle fibers was measured using the ATPase reaction. RESULTS Morphological analysis showed that aging changes were present from the sixth decade in autopsies, and consisted of atrophy and/or type-grouping. The statistical models adjusted for females in both autopsies and biopsies were linear straight with no variation in fiber size with increasing age. The models adjusted for males in both groups were quadratic, indicating that age influenced the size of different type fibers. In males type 2 were larger than type 1 fibers, and than fibers in females. CONCLUSIONS These values might be useful as controls, helping interpretation of changes in fiber size in samples obtained from biopsies and autopsies.

Effects of eccentric and concentric training on capillarization and myosin heavy chain contents in rat skeletal muscles after hindlimb suspension

We studied the effects of different protocols of post-disuse rehabilitation on angiogenesis and myosin heavy chain (MHC) content in rat hindlimb muscles after caudal suspension. Thirty female Wistar rats were divided into five groups: (1) Control I, (2) Control II, (3) Suspended, (4) Suspended trained on declined treadmill, and (5) Suspended trained on flat treadmill. Fragments of the soleus and tibialis anterior (TA) muscles were frozen and processed by electrophoresis and immunohistochemistry (CD31 antibody). Hindlimb suspension caused reduction of capillary/fiber (C/F) ratios and contents of MHC type I (MHCI) in the soleus in parallel to increased capillary density. Flat treadmill protocols increased the content of the MHCI isoform. The C/F ratio was increased by concentric training after hypokinesis, but was not modified by eccentric training, which caused a greater reduction of capillary density compared to the other protocols. In the TA muscle, hindlimb suspension caused a non-significant increase in capillary density and C/F ratio with limited changes in MHC. The present data demonstrate that the different training protocols adopted and the functional performance of the muscles analyzed caused specific changes in capillarization and in the content of the various MHC types.

Normative data for hand grip strength in healthy children measured with a bulb dynamometer: a cross-sectional study

OBJECTIVE To present the normative hand grip strength values measured with a bulb dynamometer for children, by gender and age, and to correlate the findings with weight, height, body composition and handedness. DESIGN Cross-sectional study. PARTICIPANTS Data from 295 healthy children of both genders aged 6 to 13 years were analysed. METHODS Weight, height, body composition (Biodynamics model 450 bioimpedance analyser), handedness (Edinburgh scale) and grip strength measured with a bulb dynamometer (North Coast) were obtained. RESULTS Grip strength of both hands increased with age in the two genders. Grip strength was similar in boys and girls between 6 and 13 years of age. The dominant hand was stronger than the non-dominant hand [mean (standard deviation) 7.0 (2.3)psi vs 6.5 (2.1)psi], with a mean difference of 0.52psi (95% confidence interval of the difference 0.46 to 0.58). Grip strength was positively correlated with fat-free mass and height (r≥0.75). CONCLUSION This study provides normative values for hand grip strength measured with a bulb dynamometer in children aged 6 to 13 years. This dynamometer provides a simple method to measure grip strength, and the results of this study provide further evidence of its performance in the measurement of grip strength.

Morphological comparison of different protocols of skeletal muscle remobilization in rats after hindlimb suspension.

The aim of this study was to evaluate and compare the efficacy of different remobilization protocols in different skeletal muscles considering the changes induced by hindlimb suspension of the tail. Thirty‐six female Wistar rats were divided into six groups: control I, control II, suspended, suspended free, suspended trained on a declined treadmill and suspended trained on a flat treadmill. Fragments of soleus and tibialis anterior (TA) muscle were frozen and processed by different histochemical methods. The suspended soleus showed a significant increase in the proportional number of intermediate/hybrid fibers and a decrease in the number of type I fibers. Some of these changes proved to be reversible after remobilization. The three remobilization programs led to the recovery of both the proportional number of fibers and their size. The TA muscle presented a significant increase in the number and size of type I fibers and a cell size reduction of type IIB fibers, which were recovered after training on a declined treadmill and free movement. Especially regarding the soleus, the present findings indicate that, among the protocols, training on a declined treadmill was found to induce changes of a more regenerative nature, seemingly indicating a better tissue restructuring after the suspension procedure.

Propriedades mecânicas do gastrocnêmio eletroestimulado pós-imobilização

Introduction: Mechanical properties (MP) are clinically applicable tools for healthcare professionals working on the musculoskeletal system. Objectives: The aim of this study was to evaluate two protocols of neuromuscular electric stimulation (NMES) to improve MP regeneration of the myotendinous complex after segment immobilization in female rats. Materials and Methods: Fifty animals were equally distributed into five groups: Control (CG, n=10); Immobilized (IG, n=10); Immobilized and freely remobilized (IFG, n=10); Immobilized and NMES once /day (IEG1, n=10); Immobilized and MNES twice/day (IEG2, n=10). Immobilization was kept for 14 days, and remobilization was subsequently released for 10 days. NMES was applied for 10 days, post-immobilization, every morning for 10 minutes to IEG1 animals and every morning and afternoon (total 20 minutes) to the IEG2 group. After these procedures, the gastrocnemius muscle was submitted to the mechanical traction assay to evaluate stiffness, resilience, load and stretching at maximum limit MPs. Results: Immobilization reduced the MP values concerning load and stiffness (p 0.05). Conclusion: It is concluded that the gastrocnemius muscle became structurally better organized through a single NMES application and by remobilization.

Effects of 40 min 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. The right hindlimb was immobilized using a lightweight apparatus composed of two sections: (i) upper part: a small cotton T-shirt and, and (ii) lower part: a steel mesh to fix the ankle in plantar-flexion-shortened position. Fragments of the soleus and plantaris muscle were frozen and processed using histochemical and immunohistochemical methods. Limb immobilization caused important morphological alterations in skeletal muscle including: reduction in the number of type I fibers and an increase in type IIC fibers, reduction in the lesser diameter of type I, IIA and IIAD fibers and in the number of capillaries in soleus muscle. The stretching program applied for 10 days was insufficient to allow recovery from the disuse alterations in both muscles. However, after 21 days there were improved morphological characteristics, size and distribution of the different fibers.

Propriedades mecânicas do músculo gastrocnêmio de ratas, imobilizado e posteriormente submetido a diferentes protocolos de alongamento

Stretching is widely employed in physiotherapeutic clinical practice and in sportive activities; however, the mechanical alterations of the skeletal muscle generated by this technique are poorly scientifically investigated. This study evaluated the mechanical alterations suffered by the gastrocnemius muscle of young adult female Wistar rats, submitted to14 days of immobilization followed by passive manual stretching during 10 consecutive days once or twice a day. Fifty animals were equally distributed in five groups, Control (CG); Immobilized (IG); Immobilized and liberated (ILG); Immobilized and submitted to stretching once a day (IEG1); Immobilized and submitted to stretching twice a day (IEG2). The gastrocnemius muscle was analyzed by mechanical traction assay and the properties related to load and maximal and proportional stretching evaluated in addition to stiffness and resilience. Immobilization decreased load at maximal thresholds (MTL), load at proportional thresholds (LPT), stretch at maximal thresholds (SMT), stiffness and resilience were reduced in 44.4%, 34.4%, 27.6%, 64.4% and 54% respectively, compared to CG values. With subsequent free remobilization and stretching, all parameters were restored except for IEG2 in which SMT remained reduced in 31.3%, when compared to CG. It is concluded that after 14 days of segmental immobilization, individual stretching loads and free movements contribute to regain muscle mechanical properties.

Men with Early Degrees of Knee Osteoarthritis Present Functional and Morphological Impairments of the Quadriceps Femoris Muscle

ObjectiveQuadriceps muscle weakness is common in knee osteoarthritis (OA). Reasons for weakness may include atrophy, reduction in the muscle fibers number, and changes in the muscle activation. It is uncertain when these muscular changes begin to appear. Therefore, the purpose of this study was to determine whether men with early stages of knee OA already had functional and quadriceps muscle morphologic alterations. DesignForty men were divided into two groups: control group (healthy subjects) and OA group (subjects with knee OA). A biopsy of the vastus lateralis muscle was performed for morphometric analysis. Isokinetic evaluation of knee extensor torque, concentric and eccentric (90 and 180 degrees/sec), was performed simultaneously with vastus lateralis electromyographic activity evaluation. ResultsSignificant differences were found in knee extensor torque (P < 0.05) and in normalized root mean square (P < 0.01) during the eccentric contractions (both velocities), with higher values for the control group. No differences were found during concentric contractions. The OA group presented greater values of the minimum diameter of type 1 fibers and greater proportion and relative cross-sectional area of type 2b fibers (P < 0.05). ConclusionsMen with early stages of knee OA do not present alterations of concentric strength but had decreased eccentric strength and morphologic quadriceps muscle changes, indicating neuromuscular adaptations.