strenuous

"The teacher is requiring students to submit their essays by Friday. "

"My uncle ran in the city marathon last weekend. "

"I spent an hour at lunch."

"Shoveling heavy snow from the driveway after a big storm is a laborious task. "

"I have a house and a car."

"It took a lot of effort to find a decent-sized, fully-furnished apartment within walking distance of the office.   He made a conscious effort to not appear affected by the stories in the paper."

"She trained seven hours a day to prepare for the Olympics."

"Despite his age, the gardener worked with surprising vigour, quickly clearing the overgrown weeds. "

"The children were running to catch the school bus. "

"Sentence: Completing the marathon required a lot of physical exertion. "

"Newton and Einstein are two of the greats of the history of science."

"The children's energy fueled their excitement for the school trip. "