There are numerous words in the English language that can be used as synonyms for the word strenuous. Some of these include arduous, rigorous, taxing, demanding, difficult, challenging, toilsome, laborious, exhausting, burdensome, and not easy. All of these words share a common thread of suggesting that an activity or task requires a great deal of physical and/or mental effort. It is important to have a variety of synonyms for strenuous as it allows the writer or speaker to convey the same message in a more engaging and dynamic way without being repetitive. It also helps to accurately describe the level of effort or difficulty involved in a task.