The plural Variation is a lot more widespread Based on Google ngram. It is also applied for instance in Cambridge's dictionary. Practice deep breathing tactics like box respiratory – breathe in for 4 counts, hold your breath for four counts, breathe out for four counts and maintain again for 4. https://www.cureayu.com/blogs/lifestyle/6-effective-strategies-on-how-to-strengthen-your-joints-and-protect-them