Synonyms for Strenuous:

adj.

aggressive (adjective)
energetic, forceful, zealous.
ambitious (adjective)
formidable, difficult, industrious, severe.
arduous (adjective)
onerous, troublesome, trying, rough, burdensome, harsh.
busy (adjective)
lively, fussy.
combative (adjective)
cantankerous.
difficult (adjective)
grinding, wearying, fussy, cumbersome, wearisome, harsh, burdensome, severe, complex, rough, demanding, arduous, complicated, ticklish, hard, finicky, knotty, uphill, bothersome, thorny, stressful, cantankerous, tricky, toilsome, oppressive, ambitious, difficult, contrary, trying, tough, rugged, wearing, formidable, adverse, onerous, laborious, tight, troublesome.
dynamic (adjective)
potent, powerful, zippy.
effortful (adjective)
effortful.
energetic (adjective)
kinetic, rugged, sprightly, peppy, animated, brisk.
knockabout (adjective)
knockabout.
rough (adjective)
rough-and-tumble.
severe (adjective)
severe.
strenuous (adjective)
effortful, laborious, active, dynamic, ardent, taxing, strong, tough, toilsome, uphill, exhausting, lusty, earnest, eager, vigorous, persistent, spirited, demanding, arduous, hard, determined.
vigorous (adjective)
fiery, zippy, fervent, emphatic, zestful, full-blooded, animated, passionate, burning, lusty, energetic, afire, eager, powerful, frisky, excited, hearty, virile, agitated, potent, peppy, ardent, sprightly, puissant, lively, active, enthusiastic, earnest, vigorous, spirited, mettlesome, zealous, exuberant, ablaze, industrious, impassioned, prolific, strong.

n.

driven, persistent, motivated, dedicated, sedulous, insistent, ambitious, determined, purposeful, competitive. rough-and-tumble, knockabout, action, be an effort, taxing. dynamical, dynamic, brisk, kinetic, forceful. arduous (noun)
study at active, exhausting.
strenuous (noun)
effortful, arduous, energetic, straining.

Other synonyms:

dynamical, knockabout, rough-and-tumble. kinetic, dynamic. forceful, brisk. Other relevant words:
forceful, kinetic, motivated, sedulous, determined, straining, ambitious, persistent, action, knockabout, taxing, dynamical, competitive, effortful, purposeful, rough-and-tumble, exhausting, brisk, dynamic, insistent, dedicated, driven.

Usage examples for strenuous

  1. Week after week elapsed in fruitless search, yet the duke was strenuous in continuing the pursuit. – A Sicilian Romance by Ann Radcliffe
  2. You would not have expected to find me engaged in anything so strenuous as this? – The Girl From Keller's Sadie's Conquest by Harold Bindloss