Learn Swedish: Man ska träna hjärtat. - You should exercise your heart.

man is a generic pronoun used to talk about people in general. In English, we usually say "you" (as in "you need to breathe to live") or "one" ("one should exercise"). If you used du here, it would sound like a direct instruction to the specific person you are talking to, rather than general advice.

Why does it say hjärtat (the heart) instead of a word for "your heart"?

In Swedish, when you talk about body parts or personal items, you usually just use the definite form (like hjärtat for "the heart") if it's obvious who it belongs to. Since the sentence is about people in general doing the exercising, it's already understood that they are exercising their own hearts.

Why is the verb träna in its infinitive form instead of the present tense tränar?

Because it follows the helper verb ska. Just like in English, helper verbs are paired with the infinitive (base) form of the main verb without an extra marker. You say "should exercise" in English, and in Swedish it's ska träna.

Does ska mean "should" or "will" in this sentence?

It can mean either depending on the context! While ska is frequently used for future plans ("will" or "are going to"), it is also widely used to express what someone is supposed to do, a rule, or a strong recommendation ("should"). Here, it acts as general health advice.