The drive threory of motivation is based on the principle that organisms have certain psycological or physiological needs (in this case, hunger). When those needs are not satisfied, a tension in the organism is produced, and with it a drive to seek the satisfaction of that need.
Because the substance the rat recieves is nonnutritive (it doesn't reduce the rat's hunger), we can clearly see that the rat isn't performing the response because of this drive, seeking for the satisfaction of its hunger, but is motivated by another feeling. Therefore, this observation is problematic for the drive theory of motivation.
Due to their immense oxygen needs, slow-twitch fibers are associated with many blood vessels, mitochondria, and increased concentrations of myoglobin, an oxygen-binding protein in the blood that provides muscles their reddish coloring.
