strenuous Synonyms

arduous straining tensional tiring tireless toilful toilsome tough trying taxing strong stressful spirited sedulous rigorous resolute punishing unwearied uphill upstream back-breaking on the go hard-working red-blooded peppy knockabout gruelling grueling backbreaking zealous wearying wearisome weariless wearing vigorous physical onerous murderous energetic enepidermic eager dynamical dynamic draining difficult determined demanding conscionable concerted concentrated