Máxima fase estável de lactato é ergômetro-dependente em modelo experimental utilizando ratos

EFFECT OF AEROBIC AND ANAEROBIC TRAINING ON DIFFERENT ERGOMETERS IN RAT MUSCLE AND HEART TISSUES

Objective

Analyze the effects of aerobic and anaerobic training on different ergometers on muscle and cardiac hypertrophy in rats.

Methods

The animals were separated into the following groups: Control (C), Aerobic Training in Water (ATW), Resistance Training in Water (RTW), Aerobic Training on Treadmill (ATT), and Resistance Training in Climbing (RTC). All training protocols were carried out for 4 weeks, 3 times/week. The cross-sectional area (CSA) of the gastrocnemius muscle cells and the areas of the cardiomyocytes were measured.

Results

In the fast-twitch fibers, there was an increase in CSA in the RTW and RTC groups compared to the ATW (p<0.01 and p<0.01) and ATT groups (p<0.01 and p<0.01). In the slow-twitch fibers, the ATW and ATT groups demonstrated a lower CSA compared to the RTW (p=0.03 and p<0.00) and RTC groups (p<0.01 and p<0.01). In the cardiomyocytes, there was an increase in the area of the RTW and RTC groups compared to groups C (p<0.01; p<0.01), ATW (p=0.02; p<0.01), and ATT (p<0.01; p<0.01).

Conclusion

The anaerobic training effectively promotes hypertrophy in the fast-twitch fibers and the cardiomyocytes. Level of Evidence V; Animal experimental study .

Reversal of diabetic-induced myopathy by swimming exercise in pregnant rats: a translational intervention study

Gestational diabetes mellitus (GDM) plus rectus abdominis muscle (RAM) myopathy predicts long-term urinary incontinence (UI). Atrophic and stiff RAM are characteristics of diabetes-induced myopathy (DiM) in pregnant rats. This study aimed to determine whether swimming exercise (SE) has a therapeutic effect in mild hyperglycemic pregnant rats model. We hypothesized that SE training might help to reverse RAM DiM. Mild hyperglycemic pregnant rats model was obtained by a unique subcutaneous injection of 100 mg/kg streptozotocin (diabetic group) or citrate buffer (non-diabetic group) on the first day of life in Wistar female newborns. At 90 days of life, the rats are mated and randomly allocated to remain sedentary or subjected to a SE protocol. The SE protocol started at gestational day 0 and consisted of 60 min/day for 6 days/week in a period of 20 days in a swim tunnel. On day 21, rats were sacrificed, and RAM was collected and studied by picrosirius red, immunohistochemistry, and transmission electron microscopy. The SE protocol increased the fiber area and diameter, and the slow-twitch and fast-twitch fiber area and diameter in the diabetic exercised group, a finding was also seen in control sedentary animals. There was a decreased type I collagen but not type III collagen area and showed a similar type I/type III ratio compared with the control sedentary group. In conclusion, SE during pregnancy reversed the RAM DiM in pregnant rats. These findings may be a potential protocol to consider in patients with RAM damage caused by GDM.

Effect of Aerobic Physical Exercise in an Animal Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a condition caused by an amendment to the X chromosome, inherited as a recessive trait, and affects 1:3500 live births, especially males. Low-intensity exercise is known to decrease certain parameters associated with muscular degeneration in animal models of progressive muscular dystrophies. In the present study, 28-day-old male mdx and wild-type (wild) mice were used. The animals were subjected to a low-intensity physical exercise protocol for 8 weeks. It was found that this protocol was able to reduce oxidative stress in muscle tissue and in most of the CNS structures analyzed, with a significant increase in antioxidant activity in all analyzed structures. It is thus possible to infer that this exercise protocol was able to reduce oxidative stress and improve the energy metabolism in brain tissue and in the gastrocnemius muscle of animals with DMD.

Effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue: analysis by Raman spectroscopy, dual-energy X-ray absorptiometry, and mechanical resistance

The aim of the present study was to verify the effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue by Raman spectroscopy (Raman), dual-energy X-ray absorptiometry (DXA), and mechanical resistance (F-max) analysis. A total of 40 male Wistar animals, 60 days old, were used. The animals were distributed into four groups: control (C), control with GH (GHC), muscular strength training (T), and muscular strength training with GH (GHT). Blood samples were collected for the quantification of creatine kinase (CK-MB) and the femurs were removed for analysis by Raman, DXA, and F-max. A more pronounced increase in the bone mineral components was verified in the T group, for all the variables obtained by the Raman (calcium, phosphate, amide, and collagen). In addition, for animals submitted to GH supplementation, there was a reduction in the variable bone mineral density (BMD) obtained by the DXA (p < 0.05). Finally, the animals that received GH supplementation presented a higher F-max, but without statistical significance (p > 0.05). It was concluded that animals that received GH supplementation demonstrated a decrease in BMD. In addition, T alone was able to promote increased calcium, phosphate, amide, and collagen compounds in bone tissue.

Evaluation of efforts in untrained Wistar rats following exercise on forced running wheel at maximal lactate steady state

[Purpose]

We aimed to examine the effect of running speed on metabolic responses associated with maximal lactate steady state (MLSS) in rats during forced running wheel (FRW) exercise.

[Methods]

Forty male adult Wistar rats were divided into seven groups. The blood lactate threshold and peak running speed were determined for an incremental power test group. Five groups participated in constant power tests at intensities 10, 13, 14.5, 16, and 17.5 m/min to determine MLSS and a non-exercise group was chosen as the control. Animals were euthanized immediately after constant power tests and their corticosterone, non-esterified fatty acid (NEFA), blood glucose, and creatine kinase (CK) levels analyzed. The differences among groups were identified by one-way analysis of variance (p < 0.05).

[Results]

Blood lactate threshold corresponded a running intensity of 15 m/min, while MLSS was determined to be 16 m/min. Serum corticosterone concentrations were significantly higher in 14.5, 16, and 17.5 m/min groups (298.8±62, 338.3±65, and 354±26 nM, respectively) as compared to that in the control group (210.6±16 nM). Concentrations of NEFA observed in groups 13, 14.5, 16, and 17.5 m/min (662.8±24, 702.35±69, 718.4±34, and 752.8±77 μM, respectively) were significantly higher than those in 10 m/min and control groups (511.1±53 and 412.1±56 μM, respectively). The serum CK concentration recorded for group 17.5 m/min (372.4±56 U/L) was higher than those recorded for other groups.

[Conclusion]

The speed above 16 m/min on FRW resulted in increased physiological demands and muscle damage in untrained healthy Wistar rats.

Lactate minimum underestimates the maximal lactate steady-state in swimming mice

The intensity of lactate minimum (LM) has presented a good estimate of the intensity of maximal lactate steady-state (MLSS); however, this relationship has not yet been verified in the mouse model. We proposed validating the LM protocol for swimming mice by investigating the relationship among intensities of LM and MLSS as well as differences between sexes, in terms of aerobic capacity. Nineteen mice (male: 10, female: 9) were submitted to the evaluation protocols for LM and MLSS. The LM protocol consisted of hyperlactatemia induction (30 s exercise (13% body mass (bm)), 30 s resting pause and exhaustive exercise (13% bm), 9 min resting pause and incremental test). The LM underestimated MLSS (mice: 17.6%; male: 13.5%; female: 21.6%). Pearson's analysis showed a strong correlation among intensities of MLSS and LM (male (r = 0.67, p = 0.033); female (r = 0.86, p = 0.003)), but without agreement between protocols. The Bland-Altman analysis showed that bias was higher for females (1.5 (0.98) % bm; mean (MLSS and LM): 4.4%-6.4% bm) as compared with males (0.84 (1.24) % bm; mean (MLSS and LM): 4.5%-7.5% bm). The error associated with the estimated of intensity for males was lower when compared with the range of means for MLSS and LM. Therefore, the LM test could be used to determine individual aerobic intensity for males (considering the bias) but not females. Furthermore, the females supported higher intensities than the males. The differences in body mass between sexes could not explain the higher intensities supported by the females.

Concurrent training effect on muscle fibers in Wistar rats

The aim of the present study was to determine the modeling of muscle fibers in rats submitted to different exercise protocols. Fifty-five Wistar rats were submitted divided into four different groups: Control group (CG; N=16); endurance training group (ETG; N=13), strength training group (STG; N=13) and concurrent training group (CTG; N=13). The intensity of endurance training was determined by the critical workload. Statistical analysis involved the Kruskal-Wallis test for multiple comparisons, followed by Dunn's post test (p<0.05). All animals submitted to training exhibited an increase in the cross-sectional area of the muscle fibers. The largest increase (p>0.05) occurred in the STG and CTG at both four (mean:2952,95 ± 878,39 mean:2988,84 ± 822,58) and eight weeks respectively (mean:3020,26 ± 800.91; mean:3104,91 ± 817,87). The findings demonstrate similar results obtained with strength training and concurrent training, with a greater increase in muscle fiber area in both groups in comparison to the control group and group submitted to endurance training.

Ácido Láctico como indicativo de aptidão física em ratos

INTRODUÇÃO: Os modelos experimentais são utilizados para simulações de situações relacionadas ao treinamento físico. OBJETIVO: O objetivo do presente estudo foi verificar a aptidão física de ratos em treinamento através da avaliação das concentrações de ácido láctico sérico. METODOLOGIA: Foi realizado estudo experimental utilizando 40 ratos machos Wistar, adultos, divididos em cinco grupos de oito indivíduos, havendo um grupo controle. Foi realizado o primeiro teste de esforço máximo (TE) após uma semana de familiarização com a esteira rolante e antes do primeiro dia de treinamento. Os testes de esforço seguintes foram feitos a cada 10 dias de treinamento. No final de cada teste de esforço foi coletado 1ml de sangue para medir o ácido láctico. O teste t de Student foi utilizado para comparação das médias. RESULTADOS: O ácido láctico sérico diminuiu significativamente entre o primeiro e o último teste de esforço máximo nos grupos GE10, 20 e 30. No G30 pode-se demonstrar diferença significativa entre os testes inicial e final no que se refere à velocidade (p = 0,003) e tempo (p = 0,018), assim como no G40 velocidade inicial (p = 0,0006) e tempo (p = 0,0001). CONCLUSÃO: Os resultados demonstraram que ratos submetidos a treinamento físico apresentam capacidade metabólica medida pelo ácido láctico, que demonstra aptidão física e treinamento adequado com aumento do esforço físico, sendo bem tolerado até 40 dias de treinamento em esteira rolante.