Citations:arduous

needing much energy

 * 2007, John Dear, Transfiguration: A Meditation on Transforming Ourselves and Our World, page 50:
 * That search is like an arduous mountain climb. It takes preparation, discipline, effort, and determination.
 * 2007, Russell Smith, Men's Style: The Thinking Man's Guide to Dress, page 209:
 * It enabled one to carry hardy rations - cured beef and hardtack, I imagine - on arduous mountain hikes and leave one's hands free for scrabbling in the rock and bracken, whatever bracken is.

hard to traverse

 * 2000, Linda Gong Austin, Mountain Bike! Northern California: A Guide to the Classic Trails:
 * Truth is, this project was akin to the highest, steepest, longest, and most arduous mountain I've had to pedal up.
 * 2003, Madhu Bazaz Wangu, Images of Indian goddesses: myths, meanings, and models, page 158:
 * Each one of the goddess shrines in the Shimla district is situated at the peak of a mountain. The devotee must climb the arduous mountain path or several paths in order to reach it.