Learn Hardcore Spanish (Latin America): Me duele la espalda cuando llevo mi mochila pesada. - My back hurts when I carry my heavy backpack.

doler behaves like gustar, where the thing causing pain is the grammatical subject and the person feeling it is the indirect object. You need an indirect object pronoun (me, te, le, etc.) plus the verb in third person singular or plural that agrees with the subject. Since espalda is singular, we say duele.

In Me duele la espalda, what is the grammatical subject and what is the indirect object?

The grammatical subject is la espalda (the back) – it’s what does the hurting. The indirect object pronoun me indicates who experiences the pain (“to me”). There is no direct object in this construction.

Why is it Me duele la espalda and not Me duele mi espalda?

Spanish typically uses a definite article before body parts when coupled with an indirect object pronoun: me duele la espalda. You can say me duele mi espalda to emphasize possession, but the standard way to talk about aches is with the article.

Why is the verb llevar used in cuando llevo mi mochila pesada, and not traer or cargar?

llevar means “to carry” or “to wear/carry on your person” and fits contexts where you transport something from one place to another or have it on your back. traer means “to bring” (toward the speaker), and cargar can also mean “to load” or “to bear a heavy burden” but feels more formal or literal. In everyday speech, llevar la mochila is most natural.

Why does pesada come after mochila, and why does it end in -a?

Most Spanish adjectives follow the noun. They must agree in gender and number with that noun. mochila is feminine and singular, so the adjective takes the feminine singular form pesada.

Why do we use the simple present tense llevo instead of the present progressive estoy llevando?

In Spanish, the simple present can express habitual or general truths, not just actions happening at this moment. Here, llevo means “whenever I carry” (habitual), so it’s more appropriate than estoy llevando, which suggests an action in progress right now.

Could I drop the possessive mi and say cuando llevo mochila pesada?

Yes, grammatically it’s correct and means “when I carry a heavy backpack” (any heavy backpack). Omitting mi makes it non-possessive/indefinite. If you want to specify it’s yours, keep mi mochila pesada.

How else can I express “my back hurts from carrying a heavy backpack” using por?

You can say Me duele la espalda por llevar una mochila pesada. Here, por + infinitive (por llevar) indicates the cause (“because of carrying…”).