Excessive exertion; so much exertion that discomfort or injury results(noun)
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Use "overexertion" in a sentence
"Keeping dry and comfortable without overexertion is the key to an all out day in the most frigid conditions."
"The consequences of short-term overexertion with regard to the daily working time were considered negligible, and it was assumed that a doubling of the tractive effort (e.g. for pulling vehicles uphill) could best be compensated for by cutting the speed in half."
"Fran Crippen, the former University of Virginia swimmer, died of "overexertion," United Arab Emirates swimming officials said in Dubai."