Learn Hardcore Portuguese (Portugal): Se não aqueceres os músculos, podes magoar‑te quando correres. - If you don’t warm up your muscles, you can hurt yourself when you run.

aqueceres, podes, correres are all 2nd person singular forms (informal tu), so tu is understood.
The full version would be:
Se (tu) não aqueceres os músculos, (tu) podes magoar‑te quando (tu) correres.

You normally add tu only for emphasis, contrast, or clarity, e.g.:

Se tu não aqueceres os músculos, podes magoar‑te… (emphasizing you, not someone else).

What tense are aqueceres and correres, and why are they used after se and quando?

Both aqueceres and correres are in the future subjunctive (futuro do conjuntivo).

In European Portuguese, the future subjunctive is very common after conjunctions like:

se (if)
quando (when)
logo que, assim que (as soon as), etc.

when they refer to the future:

Se não aqueceres os músculos… → If you don’t warm up your muscles (in the future) …
…quando correres. → …when you run (in the future).

English uses the present tense in these clauses, but Portuguese prefers the future subjunctive to show the action is in the future and somewhat uncertain (it may or may not happen).

Could you use the normal present tense (não aqueces, quando corres) instead? Would it sound wrong?

You can use the present indicative, but the meaning shifts:

Se não aqueceres os músculos, podes magoar‑te quando correres.
→ Focus on a future situation: If (in the future) you don’t warm up, you might hurt yourself when you run.
Se não aqueces os músculos, magoas‑te quando corres.
→ Sounds more like a general/habitual fact: If you don’t (usually) warm up, you (generally) hurt yourself when you run.

For a warning about a future event, the future subjunctive (aqueceres, correres) is the natural, standard choice in European Portuguese. Using the present indicative there is not ungrammatical, but it changes the nuance.

How is the future subjunctive formed from verbs like aquecer and correr?

The future subjunctive in Portuguese is generally formed from the 3rd person plural of the preterite (simple past):

Take the “eles” preterite form.
Remove -am.
Add the endings (which mostly match the infinitive).

For aquecer:

Preterite eles: aqueceram
Remove -am → aquecer-
Future subjunctive:
- eu: aquecer
- tu: aqueceres
- ele/ela/você: aquecer
- nós: aquecermos
- eles/elas/vocês: aquecerem

For correr:

Preterite eles: correram
Remove -am → correr-
Future subjunctive:
- eu: correr
- tu: correres
- ele/ela/você: correr
- nós: corrermos
- eles/elas/vocês: correrem

So aqueceres and correres are tu forms of the future subjunctive.

Why is it os músculos and not os teus músculos for “your muscles”?

In Portuguese, when talking about body parts (and also clothing), it’s very common to use the definite article instead of a possessive, if the owner is clear from context:

os músculos = the muscles → often understood as your muscles here.
English normally needs “your”, but Portuguese often doesn’t.

You could say:

Se não aqueceres os teus músculos…

but that tends to sound more emphatic or contrastive (e.g. your muscles, not someone else’s). In a neutral sentence like this, os músculos is more natural.

Why is magoar‑te written with a hyphen, and why does te come after magoar instead of before podes?

te is a clitic pronoun (unstressed object pronoun) meaning “yourself” (tu form). Clitics in Portuguese:

Can appear before a finite verb (proclisis): te podes magoar
Or after certain verb forms with a hyphen (enclisis): magoar‑te

In this sentence:

podes is the conjugated verb (present of poder)
magoar is an infinitive, governed by podes

In European Portuguese, with a modal like poder + infinitive, both are possible:

podes magoar‑te (very common, feels neutral or slightly more standard)
te podes magoar (also possible)

The version given, podes magoar‑te, uses enclisis with the infinitive, which is very idiomatic in EP. The hyphen simply marks that te is attached to magoar.

Is podes magoar‑te closer to “you can hurt yourself” or “you might hurt yourself”? What’s the nuance of poder here?

In this context, podes magoar‑te is more about possibility/risk than ability:

It’s best translated as “you might hurt yourself” or “you could hurt yourself” (warning).
Literally, podes = you can, but in Portuguese poder often covers both:
- ability (can),
- and possibility (may, might, could).

So the sentence is a warning about what may happen, not about whether you are physically capable of hurting yourself.

If you wanted a more neutral “you are able to hurt yourself” (which is odd here), you’d need extra context to make it sound natural.

Could the sentence also be Se não aqueceres os músculos, magoas‑te quando correres? What’s the difference?

Yes, that sentence is grammatically correct, but the nuance changes:

Original:
Se não aqueceres os músculos, podes magoar‑te quando correres.
→ If you don’t warm up your muscles, you might hurt yourself when you run.
— Emphasizes risk/possibility.
Alternative:
Se não aqueceres os músculos, magoas‑te quando correres.
→ If you don’t warm up your muscles, you hurt yourself when you run.
— Sounds more like a regular or predictable consequence (almost like a rule or habit).

For a general warning, the version with podes is more natural.

Why is the negative não placed before aqueceres and not somewhere else?

In Portuguese, the basic rule for simple negation is:

Put não directly before the conjugated verb.

Here, in the if‑clause, the conjugated verb is aqueceres:

Se não aqueceres os músculos…

If you explicitly used the subject pronoun, it would be:

Se tu não aqueceres os músculos…

So the order is: se (conjunction) + subject (optional) + não (negation) + verb.

You wouldn’t say Se aqueceres não os músculos – that would be ungrammatical.

Is this specifically European Portuguese? Would Brazilian Portuguese say this differently?

The sentence is clearly European Portuguese in flavour, but the structure is mostly valid in Brazilian Portuguese with some differences in usage:

Future subjunctive (aqueceres, correres) after se and quando
→ also used in Brazil, so that part is the same.
Pronoun form and position:
- EP: podes magoar‑te (clitic after infinitive with hyphen)
- BP normally uses você and se instead of tu and te, and places the pronoun before the verb in speech:
  - Se você não aquecer os músculos, você pode se machucar quando correr.
Verb choice:
- magoar‑se is understood in Brazil but machucar‑se (or ferir‑se) is more common there for “hurt oneself”.
Subject pronoun:
- EP often omits tu.
- BP more frequently uses você explicitly: Se você não aquecer…

So the given sentence is standard, natural European Portuguese; Brazilian Portuguese would typically adjust the pronouns, verb choice, and clitic position.