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March 28, 1925


JAMA. 1925;84(13):999-1000. doi:10.1001/jama.1925.02660390067019

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The Amount of Energy Expended by Mental Work  In a series of very carefully conducted experiments on six subjects accustomed to mental work, Ilzhofer of Munich has been investigating the amount of energy expended by lighter and heavier forms of mental work. In his estimates he followed the Krogh method of computation. During the performance of the mental work, the various experimental subjects, who assumed an extended supine position, were observed to present more or less individual peculiarities of breathing. During intense mental work, respiration in all subjects became accelerated, and in many persons more irregular than under conditions of mental rest or during light mental employment. Taking the energy used during mental rest as a standard for comparison, the caloric expenditure during light mental work increased, on the average, 1.6 per cent., and during intense mental work, 5 per cent. In the first case, the increase was very slight—scarcely

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