Noun
The act of exerting, or putting into motion or action; the active exercise of any power or faculty; an effort, esp. a laborious or perceptible effort; as, an exertion of strength or power; an exertion of the limbs or of the mind; it is an exertion for him to move, to-day.
Source: Webster's dictionaryKnowledge is not a passion from without the mind, but an active exertion of the inward strength, vigour and power of the mind, displaying itself from within. Ralph Cudworth
A multitude of causes unknown to former times are now acting with a combined force to blunt the discriminating powers of the mind, and unfitting it for all voluntary exertion to reduce it to a state of almost savage torpor. William Wordsworth
Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. Harriet Beecher Stowe
I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago. Edgar Allan Poe
In speaking of the work of machines and of natural forces we must, of course, in this comparison eliminate anything in which activity of intelligence comes into play. The latter is also capable of the hard and intense work of thinking, which tries a man just as muscular exertion does. Hermann von Helmholtz
A spade may be made of any size, and if the same number of strokes be made in the hour, the requisite exertion will vary nearly as the cube of the length of the blade. William Stanley Jevons