Exercício vinculado ao alimento: um método de laboratório mais próximo da natureza

Abstract

The survival of some species in nature involves physical activities related to obtaining food, reproduction, and to escape predators. This physiological link between physical activity and food intake has not been taken into account in most studies investigating the mechanisms related to energy homeostasis. Therefore, the aims of this study were: 1) to propose an experimental method that links physical activity, voluntarily performed, the supply of food (protocol 1), 2) determine the effect of this relationship in the parameters of exercise on body composition and thermoregulation (protocol 2). Methods: This study was approved by the Ethics Committee on Animal Experimentation of the Federal University of Minas Gerais (protocol 180/10). In protocol 1, 5 animals were kept for 164 days in individual cages of activity, during 147 days the exercise was synchronized with food. The cost for food was increased by 15%, every three days. In protocol 2, 15 animals were divided in three groups, one group where the animals had free access without link between activity and food (SV), a group with free access to the wheel, with the link between exercise and food (CV) and group kept in standard housing, without access to the activity (SED). The animals were kept for 73 to 75 days in the experiment. In the CV group, the cost for food was gradually increased by 90%, every three days. In both protocols (1 and 2) the main parameter used for determining the amount of maximum daily strain was 15% to 20% of reduction in body mass. In protocol 3, 7 animals underwent implantation of the sensor in the region and intraperitoneal, after recovery, the colonic temperature was measured for 65 minutes. In the first 5 minutes, the animals were restrained and the probe temperature was set manually, the following 60 minutes, the animals could move freely in the cage e the temperature probe was fixed on the tail of the animal. Results: The main results of the study were: progressive increase in the distance traveled by the animals due to the increased cost to obtain food, reduction of body mass mainly related to a reduction in adipose tissue; maintenance of wet mass of the heart, liver and gastrocnemius and soleus muscle, suggesting that the experiments the animals completed in a healthy condition; reduction in colonic temperature proportional to the ratio between the food and the distance and a strong correlation between the temperatures measured in the colon and intraperitoneally. Conclusion: The method allowed the observation of physiological behaviors consistent with the hypothesis derived from observations in natural conditions, such as the fact that animals only exercise significantly if there is a biological necessity. Moreover, the method could induce mechanisms for adjusting the exercise parameters, the body mass and thermoregulation related to increased cost for obtaining food.