Strenuous (adjective)

1. Requiring or using great exertion.
2. Requiring great effort or energy.

Origin:

Late 16th century: from latin strenuus "vigorous, active" + -ous.

Examples:

1. The hike was strenuous and tiring.
2. She had a strenuous workout at the gym.
3. He had a strenuous job that required a lot of physical labor.
4. The competition was very strenuous, and the contestants were exhausted by the end of it.
5. The climb was strenuous, but the view from the top was worth it.