The sciatic and radial nerves seem to adapt similarly to different ladder-based resistance training protocols.

The present study aimed to compare the morphological response induced by different ladder-based resistance training (LRT) protocols on the peripheral nerve ultrastructure of young adult Wistar rats. Twenty-nine rodents were distributed into groups: control (CON), submaximal (SUBMAX [6 climbs/session, moderate intensity, 3x/week]) and maximum (MAX [> 4 climbs/session, maximum intensity, 3x/week]) LRT. After 8 weeks, the radial and sciatic nerves were removed and prepared for transmission electron microscopy. In the radial nerve, the myelinated fibers and axons, myelin sheath thickness, and unmyelinated axons were statistically greater in the SUBMAX and MAX. The MAX group had greater unmyelinated fibers than SUBMAX. The Schwann cell (SC) nuclei diameter was statistically larger in the SUBMAX than the CON. The number of microtubules and neurofilaments was statistically higher in the SUBMAX and MAX. In the sciatic nerve, the myelinated fibers, myelinated and unmyelinated axons, and myelin sheath thickness were statistically greater in the SUBMAX and MAX. The SUBMAX and MAX had more SC at the nuclei level than CON. The SC nuclei were statistically larger in the SUBMAX and MAX. The number of microtubules and neurofilaments was statistically higher in the SUBMAX and MAX. Total training load and total load per climb were not different between groups. The SUBMAX and MAX statistically increased maximum carried load (ML). In conclusion, the different LRT protocols induced similar morphological responses in radial and sciatic nerves, probably due to load progression and equal total load volume.

Muscle hypertrophy is correlated with load progression delta, climb volume, and total load volume in rodents undergoing different ladder-based resistance training protocols.

We compared the effects of two ladder-based resistance training (LRT) protocols on the skeletal muscle morphology (biceps brachialis and plantaris) of Wistar rats. Also, we correlated the training parameters with the muscle fiber cross-sectional area (fCSA). After maximum load tests (ML), twenty-nine young adult Wistar rats were divided into: CONTROL (n = 9), LIMITED (n = 10, 6-8 climb [2 × 50 %ML, 2 × 75 %ML, 2 × 100 %ML, and 2 × 100 %ML+30 g]) and UNLIMITED (n = 10, ≥4 climbs [50 %ML, 75 %ML, 90 %ML, 100 %ML + 30 g until failure) LRT. After eight weeks, the main results were: 1) For biceps brachialis, the type I, IIa, and mean fCSA was statistically larger in the LIMITED than CONTROL. The nuclei/fiber ratio was statistically higher in the LIMITED and UNLIMITED. The correlations found between total load, absolute delta load, and relative load and fCSA were moderate. 2) For plantaris, the type I, IIa, IIx/b, and mean fCSA was statistically larger in the LIMITED than CONTROL. The type IIa, IIx/b, and mean fCSA was statistically larger in the UNLIMITED than CONTROL. The nuclei/fiber ratio was statistically higher in both trained groups than CONTROL. The correlation between the climbing number, total load, and the fCSA was moderate. The correlation between delta absolute load and fCSA was strong. We concluded that rodents submitted to high-intensity, high-volume LRT, but limited climbing volume per session, presented more significant type I, IIa, IIx/b, and mean fCSA, higher nuclei/fiber ratio, and greater maximum carrying capacity. Also, muscle hypertrophy correlated positively with the load progression, training volume, and total load.

Effects of resistance training on liver structure and function of aged rats.

The aging process may cause negative physiological changes. However, exercises as resistance training (RT) have been considered an important intervention to attenuate these changes. Additionally, liver plays an important role in blood glucose homeostasis in exercise. AIM: This study aimed to analyze the effects of RT on the liver components of aged animals. METHODS: Male Wistar rats were divided into two groups: 24 months' group (CONTROL); and group submitted to a progressive RT protocol for 16 weeks (EXERCISE). Both groups were sacrificed at 24 months. RESULTS: We observed a decrease in blood flow due to the practice of resistance exercises. Besides, our results showed that hepatic tissue plays an important role in glycemic homeostasis during RT. In addition, RT increased mitogen capacity of hepatocytes. CONCLUSIONS: Our study showed many implications for the knowledge about the effects of strength training on old animals' liver.

Effects of testosterone administration on liver structure and function in aging rats.

Aging males have a decrease in testosterone levels, by which the testosterone treatment may influence in a negatively fashion the liver. AIM: This study aimed to analyze the effects of aging with or without testosterone administration on the liver components of animals. METHODS: Wistar rats were divided into three groups: 20 months' group (G20), 24 months' group (G24), group treated with testosterone for 16 weeks (GT). All groups were sacrificed at 24 months except for G20 that was sacrificed at 20 months. RESULTS: Aging and testosterone treatment alters the body weight (BW), liver weight (LW) and relative liver weight. Besides, testosterone increased the mitogen capacity of hepatocytes. Nonetheless, we reinforce the negative effects of testosterone on old animals' liver as chronic hepatic congestion and/or cholestasis. In addition, we observed that testosterone plays an important role on hepatic glycogen stores. CONCLUSIONS: Our study showed many implications for the knowledge about the effects of aging with or without testosterone administration on old animals' liver.

MORPHOLOGICAL ADJUSTMENTS OF THE RADIAL NERVE ARE INTENSITY-DEPENDENT / AJUSTES MORFOLÓGICOS DO NERVO RADIAL SÃO DEPENDENTES DE INTENSIDADE / AJUSTES MORFOLÓGICOS DEL NERVIO RADIAL SON DEPENDIENTES DE INTENSIDAD

ABSTRACT Introduction: Peripheral nerve adaptation is critical for strength gains. However, information about intensity effects on nerve morphology is scarce. Objective: To compare the effects of different intensities of resistance training on radial nerve structures. Methods: Rats were divided into three groups: control (GC), training with 50% (GF1) and training 75% (GF2) of the animal’s body weight. The morphological analysis of the nerve was done by light and transmission electron microscopy. One-way ANOVA and the Tukey’s post hoc test were applied and the significance level was set at p≤0.05. Results: Training groups had an increase of strength compared to GC (p≤0.05). All measured nerve components (mean area and diameter of myelin fibers and axons, mean area and thickness of the myelin sheath, and of neurofilaments and microtubules) were higher in GF2 compared to the other (p≤0.05). Conclusion: Results demonstrated greater morphological changes on radial nerve after heavier loads. This can be important for rehabilitation therapies, training, and progression.

RESUMO Introdução: A adaptação dos nervos periféricos é fundamental para ganhos de força. No entanto, as informações relativas aos efeitos da intensidade sobre a morfologia do nervo são escassas. Objetivo: Comparar os efeitos de diferentes intensidades de treinamento de resistência sobre estruturas do nervo radial. Métodos: Os ratos foram divididos em três grupos: controle (GC) e treinamento com 50% (GF1) e 75% (GF2) do peso corporal do animal. A análise morfológica do nervo foi feita com microscopia óptica e eletrônica de transmissão. A one-way ANOVA e o teste post hoc de Tukey foram aplicados e o nível de significância foi estabelecido em p ≤ 0,05. Resultados: Os grupos treinamento tiveram aumento de força com relação ao GC (p ≤ 0,05). Todos os componentes medidos do nervo (área média e diâmetro de fibras de mielina e axônios, área média e espessura da bainha de mielina, neurofilamentos e microtúbulos) foram maiores no GF2 em comparação com os demais (p ≤ 0,05). Conclusão: Os resultados demonstraram maiores alterações morfológicas no nervo radial depois de cargas mais pesadas. Isso pode ser importante para terapias de reabilitação, treinamento e progressão.

RESUMEN Introducción: La adaptación de los nervios periféricos es fundamental para el aumento de fuerza. Sin embargo, la información sobre el efecto de la intensidad sobre la morfología del nervio es escasa. Objetivo: Comparar el efecto de diferentes intensidades de entrenamiento de resistencia en las estructuras del nervio radial. Métodos: Las ratas se dividieron en tres grupos: control (GC) y entrenamiento con 50% (GF1) y con 75% (GF2) del peso corporal del animal. El análisis morfológico del nervio se hizo con microscopía óptica y electrónica de transmisión. Se aplicaron la prueba ANOVA de una vía y la prueba post hoc de Tukey y el nivel de significación se fijó en p ≤ 0,05. Resultados: Los grupos de entrenamiento tuvieron aumento de la fuerza con respecto al grupo control (p ≤ 0,05). Todos los componentes medidos del nervio (área media y diámetro de las fibras de mielina y axones, área media y espesor de la vaina de mielina, neurofilamentos y microtúbulos) fueron mayores en GF2 en comparación con los otros grupos (p ≤ 0,05). Conclusión: Los resultados mostraron mayores cambios morfológicos en el nervio radial después de las cargas más pesadas. Esto puede ser importante para terapias de rehabilitación, entrenamiento y progresión.

Aging Induces Changes in the Somatic Nerve and Postsynaptic Component without Any Alterations in Skeletal Muscles Morphology and Capacity to Carry Load of Wistar Rats.

The present study aimed to analyze the morphology of the peripheral nerve, postsynaptic compartment, skeletal muscles and weight-bearing capacity of Wistar rats at specific ages. Twenty rats were divided into groups: 10 months-old (ADULT) and 24 months-old (OLD). After euthanasia, we prepared and analyzed the tibial nerve using transmission electron microscopy and the soleus and plantaris muscles for cytofluorescence and histochemistry. For the comparison of the results between groups we used dependent and independent Student's t-test with level of significance set at p ≤ 0.05. For the tibial nerve, the OLD group presented the following alterations compared to the ADULT group: larger area and diameter of both myelinated fibers and axons, smaller area occupied by myelinated and unmyelinated axons, lower numerical density of myelinated fibers, and fewer myelinated fibers with normal morphology. Both aged soleus and plantaris end-plate showed greater total perimeter, stained perimeter, total area and stained area compared to ADULT group (p < 0.05). Yet, aged soleus end-plate presented greater dispersion than ADULT samples (p < 0.05). For the morphology of soleus and plantaris muscles, density of the interstitial volume was greater in the OLD group (p < 0.05). No statistical difference was found between groups in the weight-bearing tests. The results of the present study demonstrated that the aging process induces changes in the peripheral nerve and postsynaptic compartment without any change in skeletal muscles and ability to carry load in Wistar rats.