Synonyms of strenuous

Adjective

1. strenuous, energetic (vs. lethargic)

usage: characterized by or performed with much energy or force; "strenuous exercise"

2. arduous, straining, strenuous, effortful (vs. effortless)

usage: 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

Definition and meaning of strenuous (Dictionary)