Eagerly pressing or urgent; zealous; ardent; earnest; bold; valiant; intrepid; as, a strenuous advocate for national rights; a strenuous reformer; a strenuous defender of his country.
taxing to the utmost; testing powers of endurance; "his final, straining burst of speed"; "a strenuous task"; "your willingness after these six arduous days to remain here"- F.D.Roosevelt