Questions & Answers about Við getum teygt stífa vöðva oft.
Why is the verb 'to stretch' written as teygt instead of the infinitive teygja?
It is because of the verb geta (here as getum), meaning 'can'. In Icelandic, geta always requires the following main verb to be in the supine form (the sagnbót). For teygja, the supine form is teygt.
How do we know vöðva is plural here? The singular form looks exactly the same!
You are right to be suspicious. For weak masculine nouns like vöðvi, the word vöðva can be singular (accusative, dative, or genitive) as well as plural (accusative or genitive). The giveaway is the adjective attached to it! Stífa is the masculine plural accusative form of stífur (stiff). If it were singular, the phrase would be stífan vöðva.
Why is the phrase stífa vöðva in the accusative case?
It acts as the direct object of the verb teygja (to stretch). The thing that is being stretched takes the accusative case.
Could the adverb oft (often) go somewhere else in this sentence?
Yes! While putting adverbs of frequency at the very end of the sentence is common and natural, you can also place oft right after the conjugated verb. So, Við getum oft teygt stífa vöðva is also perfectly correct.