Treinamento em natação com baixa intensidade não protege músculo esquelético contra lesões induzidas por exercício exaustivo em ratos

Abstract

While regular aerobic exercise promotes beneficial adaptations to the skeletal muscle, acute exhaustive exercise causes structural damage to the skeletal muscle cells. The aim of this study was to verify whether a low-intensity swimming program protects the skeletal muscles against damage induced by exhaustive exercise. Male Wistar rats (weight: 376.50 ± 4.36g; age: 90 days) were randomly divided into four groups: control sedentary (CS, N=8); sedentary submitted to exhaustive test (ES, N=7); swimming trained (ST, N=7); swimming trained submitted to exhaustive test (STE, N=7). Animals of TN and TNE groups were submitted to a swimming regimen without overload for 90 min/day, 5 days/wk, during 17 weeks. Forty-eight hours after the last training session, animals from SE and TNE groups were submitted to an exhaustive exercise protocol. At sacrifice, fragments of soleus and rectus femoris muscles were collected and submitted to histological analysis and heat shock protein (HSP70) expression measurement. The results showed that the time until exhaustion was greater in the STE than in SE group (125.0 6.00 vs. 90.0 8.48 min, respectively, P<0.05). The levels of blood lactate during exhaustive exercise were lower in animals from TNE than SE (5.31 ± 0.22 vs. 8.76 ± 0.59 mmol/L, respectively, P<0.05)The frequency of damaged fibers in the muscles was greater in SE (soleus: 34.86±0.04; rectus femoris: 37.57 ± 0.07) and STE (soleus: 41.57±0.08; rectus femoris: 39.57 ± 0.05), compared to groups SC (soleus: 13.88±0.81; rectus femoris: 16.75 ± 0.79) and ST (soleus: 24.14±0.06; rectus femoris: 24.0 ± 0.05), respectively, (P<0.05). There was no significant difference in the HSP70 levels of the analyzed muscles among the four groups (P>0.05).In conclusion, although a low-intensity swimming training increased the animals' performance in the exhaustive exercise test, it did not protect their skeletal muscles against damage induced by exhaustive exercise.

Efeito de consumo de carboidrato e de exercício físico sobre a concentração de glicogênio

“…In contrast to the present results, another study demonstrated a reduction in lactate production in the soleus muscle of Wistar rats at the end of 8 weeks of exercise on a treadmill at an intensity of 25% above the aerobic/ anaerobic metabolic transition, compared to a group of animals trained at a velocity corresponding to the metabolic transition 15 . In a study involving adult male Wistar rats submitted to low-intensity and exhaustive swimming exercise, lactate concentrations were found to be lower in trained animals than in sedentary animals 16 . After 8 weeks of swimming exercise at 80% of maximum load, a reduction in blood lactate concentration was identified when compared to the group of sedentary animals 17 .…”