In the swimming protocols for rats, the exercise intensity is measured using overloads tied to the back of the animals, quantifying different intensities of effort. The most used methodology for prescription of the overload uses the rat body weight as parameter. So, this procedure of overload prescription can be susceptible to the imprecision in obese animals, since is not considered factors that can be relevant as the body composition and density of the animals. In this way, rats with larger amount of body fatty stores may show a smaller density, facilitating its flotation and swimming in a proportional smaller work intensity than normal mass rats. In the present study we propose the development of a new line of investigation using a different swimming protocol model for rats. So, in this model of evaluation, rats will swim in a tethered protocol, through which we hoped to improve the evaluation, in terms of sensibility in the overload determination (considering the corporal density), as in a new parameters of investigation associated to the swimming pattern of the animals. The rats will swim tethered through a rope elastic connected to a signs acquisition system (strain gage, data acquisition module - National Instruments, Labview software), that will be accomplished monitoring the swim impulse of the animals in a high frequency (1000 Hz) through all duration of the exercise. This study intend to use the new apparatus in the evaluation of the maximal lactate steady state in normal and induced to the obesity rats, through the cafeteria diet, to determinate the validity of this method and to test the sensibility comparing results among animals with different body compositions.
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