Antes de correr, tengo que hacer estiramientos para preparar los músculos.

In Spanish, “antes” (before) normally needs the preposition “de” before an infinitive or a noun:

• Antes de correr = Before running
• Antes de la clase = Before class

“Antes correr” is ungrammatical in this context. Think of “antes de” as a fixed chunk when it’s followed by an action (infinitive) or a thing (noun).

After prepositions like de, Spanish uses the infinitive, not a conjugated verb:

• ❌ Antes de corro
• ✅ Antes de correr (before I run / before running)

English says “before I run” (a finite verb), but Spanish uses “antes de + infinitive” to express the same idea. The subject (I) is understood from context.

Yes, but it sounds more formal or emphatic. In Spanish, the subject pronoun (yo) is usually omitted unless you want to:

• contrast: Yo tengo que hacer estiramientos, pero él no.
• emphasize: Yo tengo que hacerlo, nadie más.

So the natural version is:

• Antes de correr, tengo que hacer estiramientos.

“Tener que + infinitive” usually means “have to / must” — a necessity or obligation:

• Tengo que hacer estiramientos.
  = I have to do stretches / I must stretch.

In everyday speech, it can feel slightly softer, sometimes close to “I really should”, but grammatically it expresses obligation more than mere advice.

Alternatives:

• Debo hacer estiramientos. (I ought to / I must) – sounds a bit more formal.
• Necesito hacer estiramientos. (I need to do stretches) – focuses on need, not obligation.

Spanish often uses “hacer + noun” to describe activities:

• hacer estiramientos = do stretches
• hacer ejercicios = do exercises
• hacer yoga = do yoga

You can say:

• Antes de correr, tengo que estirarme.

That’s also correct and common: estirarse = to stretch (oneself).

Very natural options in Latin American Spanish:

• Tengo que hacer estiramientos.
• Tengo que estirarme.

The original just chooses the “do + noun” pattern.

Because we normally think of stretching as a set of several individual stretches:

• touch your toes, stretch quads, hamstrings, etc.

So Spanish usually says:

• hacer estiramientos (plural)
  like do stretches in English.

You could say hacer estiramiento (singular), but that would sound like one specific type of stretch or more technical/medical. Everyday speech generally uses the plural.

In Spanish, with parts of the body, we often use the definite article (el, la, los, las) instead of a possessive:

• Me duele la cabeza. = My head hurts.
• Me lavé las manos. = I washed my hands.
• Para preparar los músculos. = To prepare my muscles.

It’s understood that the muscles are your muscles from context, so “los músculos” is more natural than “mis músculos” here.

“mis músculos” is not wrong, but it’s less idiomatic in this context unless you want contrast or emphasis (e.g. not someone else’s muscles).

Yes, it’s grammatically correct and understandable:

• Antes de correr, tengo que hacer estiramientos para preparar mis músculos.

It just sounds a bit more explicit or emphatic about whose muscles they are. The usual “default” in this context is:

• …para preparar los músculos.

Here, “para” expresses purpose / goal:

• para preparar los músculos = in order to prepare the muscles

Para + infinitive = “in order to + verb”.

Por would suggest cause, reason, or exchange, which doesn’t fit here. You’re not doing stretches because of preparing the muscles; you do them in order to prepare them. So “para” is the correct preposition.

In Spanish, after many prepositions (like antes de, para), you must use the infinitive:

• antes de correr (before running / before I run)
• para preparar (to prepare / in order to prepare)

Also, after tengo que, the next verb is an infinitive:

• tengo que hacer (I have to do)
• tengo que preparar (I have to prepare)

So the structure is:

• antes de + infinitive
• tener que + infinitive
• para + infinitive

In real-life writing, both are seen:

• Antes de correr, tengo que hacer estiramientos.
• Antes de correr tengo que hacer estiramientos.

The comma is recommended because “Antes de correr” is an introductory clause. It makes the sentence clearer, especially in writing, but in casual texts many people omit it.

Yes:

• Antes de correr, necesito hacer estiramientos.
  = Before running, I need to do stretches.

Nuance:

• tengo que = I have to / I must (obligation)
• necesito = I need to (focus on necessity, often slightly softer)

Both are natural in Latin American Spanish; the original just chooses tengo que.

Not exactly:

• hacer estiramientos = to do stretches (specifically stretching exercises).
• calentar or hacer calentamiento = to warm up (which can include jogging, dynamic moves, stretching, etc.).

You might say:

• Antes de correr, tengo que calentar. (Before running, I have to warm up.)
• Antes de correr, tengo que hacer estiramientos. (Before running, I have to do stretches.)

Both are correct; they just focus on slightly different aspects of your pre-run routine.

Key points:

• h in hacer is silent: a-CER
• correr: both r sounds are tapped/trilled: ko-RRER (double rr = strong trill)
• estiramientos: stress on mien → es-ti-ra-mien-tos
• músculos: stress on mús → MÚS-cu-los

Whole sentence (main stresses in caps):

• AN-tes de co-RRER, TENG-o que ha-CER es-ti-ra-MIEN-tos pa-ra pre-pa-RAR los MÚS-cu-los.