Strenuous (adjective) — مُرهق ومُتعب: Requiring great effort. Below are 7 words with a similar meaning; the linked ones have full GL Dictionary entries with their meaning in Arabic.
Requiring great effort or energy; difficult and tiring; demanding considerable physical or mental exertion
requiring much effort, skill, or attention; insisting upon exact conformity to requirements; making difficult requests or requiring high standards
Extremely tiring and demanding.
Requiring much effort and time.
Strong, healthy and full of energy.
taxingtough
Up a slope; difficult.