Learn Hardcore Spanish (Latin America): Estiro cada músculo antes de hacer ejercicio intenso. - I stretch each muscle before doing intense exercise.

Estiro already clearly means “I stretch”.
Saying Yo estiro is grammatically correct, but usually only needed when you want to emphasize the “I”:

Examples:

Yo estiro cada músculo antes de hacer ejercicio intenso.
→ I (as opposed to others) stretch every muscle before doing intense exercise.
Estiro cada músculo antes de hacer ejercicio intenso.
→ Neutral statement about your habit.

Why is it estiro cada músculo and not me estiro? Don’t we usually say “I stretch” as a reflexive verb?

Spanish uses both:

estirarse (reflexive) – to stretch oneself, to stretch generally
- Me estiro antes de hacer ejercicio.
  → I stretch (my body) before I exercise.
estirar + direct object – to stretch something specific
- Estiro cada músculo antes de hacer ejercicio intenso.
  → I stretch each muscle before doing intense exercise.

The sentence you gave focuses on each muscle as a direct object, which is why it’s not reflexive:

Estiro cada músculo = I stretch each muscle (one by one).

You could say:

Me estiro bien antes de hacer ejercicio intenso.
→ More general: I stretch well before doing intense exercise.

Both are correct; the original sentence just emphasizes the individual muscles.

What’s the difference between cada músculo and todos los músculos?

Both can translate to “every muscle” / “all the muscles”, but the nuance is slightly different:

cada músculo = each muscle, one by one
- Suggests individual attention to every muscle.
- Very close to English “each muscle”.
todos los músculos = all (of) the muscles as a group
- Slightly more collective feeling, less emphasis on “one by one”.

So:

Estiro cada músculo antes de hacer ejercicio intenso.
→ You’re focusing on every single muscle individually.
Estiro todos los músculos antes de hacer ejercicio intenso.
→ You stretch all your muscles, more as a whole.

Why is it cada músculo (singular) and not cada músculos (plural)?

In Spanish, cada is always followed by a singular noun:

cada músculo (✔) – each muscle
cada día (✔) – each day
cada músculos (✘) – incorrect
cada días (✘) – incorrect

So the correct pattern is always cada + singular noun, even if in English we might say “every muscles” in a mistaken way.

Why do we say antes de hacer instead of just antes hacer?

When antes is followed by a verb in the infinitive, Spanish needs the preposition de:

antes de + infinitive
- antes de comer – before eating
- antes de dormir – before sleeping
- antes de hacer ejercicio intenso – before doing intense exercise

antes hacer without de is incorrect in this construction.

If you introduce a full clause with a conjugated verb, you use antes de que:

Estiro cada músculo antes de que empiece el ejercicio intenso.
→ I stretch every muscle before the intense exercise begins.

Why is it hacer and not hago in antes de hacer ejercicio intenso?

After antes de, the verb must be in the infinitive form:

antes de + infinitive
- antes de hacer – before doing
- antes de ir – before going
- antes de estudiar – before studying

If you used hago (I do), you’d need a different structure:

…antes de hacer ejercicio intenso. (✔)
…antes de que yo haga ejercicio intenso. (✔, with a full clause and subjunctive)
…antes de hago ejercicio intenso. (✘ incorrect)

So hacer is the correct infinitive after antes de.

Is ejercicio intenso a fixed phrase? What exactly does it mean?

Ejercicio intenso is not a fixed idiom; it’s simply a noun + adjective:

ejercicio = exercise
intenso = intense

Together: “intense exercise”.

It refers to physically demanding activity with high effort, like:

heavy weightlifting
high‑intensity interval training (HIIT)
sprinting, etc.

The adjective intenso agrees in gender and number with the noun:

ejercicio intenso (masculine singular)
sesiones intensas (feminine plural)
entrenamientos intensos (masculine plural)

Could we say ejercicios intensos instead of ejercicio intenso?

Yes, but the meaning shifts slightly:

hacer ejercicio intenso
→ to do intense exercise (exercise in general, as an activity)
hacer ejercicios intensos
→ to do intense exercises (specific exercises, probably several types)

In everyday speech in Latin America, hacer ejercicio (singular) is very common to mean “work out / exercise” as a general activity. The original sentence uses this common pattern.

Why is it hacer ejercicio and not hacer ejercicios or ejercitar?

In Latin American Spanish, the most natural, everyday way to say to exercise / to work out is:

hacer ejercicio

Examples:

Hago ejercicio todos los días. – I exercise every day.
No hago suficiente ejercicio. – I don’t exercise enough.

hacer ejercicios is also correct but usually suggests specific exercises (e.g., sit‑ups, push‑ups, drills).

ejercitar exists but is less common in casual speech for “to work out”:

Ejercito los músculos de las piernas. – I exercise/train my leg muscles.
Ejercitarse (reflexive) can mean to work out, but hacer ejercicio is more colloquial and widespread.

Can I change the word order to Antes de hacer ejercicio intenso, estiro cada músculo?

Yes, that word order is perfectly natural:

Antes de hacer ejercicio intenso, estiro cada músculo.
Estiro cada músculo antes de hacer ejercicio intenso.

Both mean the same thing. Spanish allows this kind of flexibility, and starting with Antes de… sometimes sounds a bit more narrative or explanatory: you emphasize what happens first.

How is músculo pronounced, and why does it have an accent?

músculo is pronounced approximately as:

[MOO-skoo-loh], with the stress on the first syllable: MÚS-cu-lo

The written accent (´) shows where the stress falls. Without an accent, by default a word ending in a vowel, n, or s would be stressed on the second‑to‑last syllable:

If it were written musculo (no accent), it would be read as mus-CU-lo, which is wrong.

So the accent in músculo is needed to indicate correct stress: MÚS-cu-lo.

Is ejercicio intenso the only natural option, or could I say ejercicio fuerte or something else in Latin America?

You can definitely use other adjectives; intenso is just one common choice. Some natural alternatives:

ejercicio fuerte – “hard/strong exercise” (very common, informal)
ejercicio pesado – “heavy/tough exercise”
ejercicio exigente – “demanding exercise”
ejercicio vigoroso – “vigorous exercise” (a bit more formal/technical)

All of these are understandable in Latin America. The original ejercicio intenso sounds neutral and natural in both everyday and more formal contexts.