arduous straining strenuous
arduous%5:00:02:effortful:00 straining%5:00:00:effortful:00 strenuous%5:00:00:effortful:00
energičen naporen prizadeven vztrajen
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)