Attended with great labor, like the ascending of acclivities; difficult; laborious; as, an arduous employment, task, or enterprise.
demanding great effort, labor and mental care
characterized by toilsome effort to the point of exhaustion; especially physical effort; "worked their arduous way up the mining valley"; "a grueling campaign"; "hard labor"; "heavy work"; "heavy going"; "spent many laborious hours on the project"; "set a punishing pace"