L’exercice montre comment réanimer avec le massage cardiaque.

Because exercice starts with a vowel sound. In French, le and la usually shorten before a vowel or silent h:

• le exercice → l’exercice
• la école → l’école

Also, exercice is masculine singular, so the full article would be le if there were no elision.

It can mean exercise, but in this context it is closer to training exercise, practice activity, or drill.

So L’exercice montre... suggests something like:

• the training exercise shows...
• the practice activity demonstrates...

It does not mean physical exercise in the fitness sense here.

Montre is the third-person singular present tense of montrer (to show).

So:

• je montre = I show
• tu montres = you show
• il / elle / on montre = he / she / one shows

Here, the subject is L’exercice, which is singular, so French uses montre:

• L’exercice montre = The exercise shows

After comment, French often uses an infinitive when talking about how to do something in general.

So:

• comment réanimer = how to resuscitate
• comment cuisiner = how to cook
• comment conduire = how to drive

This is very natural in French. English does the same in many cases: shows how to resuscitate.

If French wanted to use a full clause, it could, but the infinitive is the normal and concise choice here.

Not exactly. This is an important false-friend warning.

In French, réanimer commonly means:

• to revive
• to resuscitate

In English, reanimate exists, but it often sounds unusual or even like science fiction in everyday speech. In a medical context, English normally says:

• to resuscitate
• to revive

So in this sentence, réanimer is best understood as to resuscitate, not as the English-looking word reanimate.

French often leaves the object unstated when it is generic or understood from context.

So comment réanimer means:

• how to resuscitate someone
• how to perform resuscitation

French does not need to say quelqu’un here unless it wants to be more explicit:

• comment réanimer quelqu’un = how to resuscitate someone

Without an object, the meaning is still perfectly natural.

Literally, it means with cardiac massage.

In practical English, that usually means using chest compressions or using cardiac massage.

So avec here means using or by means of, not just physically being next to something.

The phrase tells you the method used for resuscitation.

Not exactly.

Le massage cardiaque literally means cardiac massage, which in modern practical terms usually refers to chest compressions.

But CPR is broader. In French, CPR is often:

• la réanimation cardio-pulmonaire
• abbreviated RCP

So:

• massage cardiaque = chest compressions / cardiac massage
• RCP = CPR as a whole

This sentence specifically mentions massage cardiaque, so it is talking about that part or technique, not necessarily the full CPR procedure in all its components.

French uses definite articles much more often than English does.

Here, le massage cardiaque does not mean a particular single massage already mentioned. It refers to the technique in a general sense:

• avec le massage cardiaque = using chest compressions / using cardiac massage

English often drops the article in this kind of general statement, but French usually keeps it.

Yes, but it would mean something slightly different.

• montre comment réanimer = shows how to resuscitate
• montre comment faire un massage cardiaque pour réanimer = shows how to do cardiac massage in order to resuscitate
• pour réanimer = to/in order to resuscitate

So comment focuses on the method: how it is done.
Pour focuses more on the purpose: what it is for.

A simple pronunciation guide is:

L’exercice montre comment réanimer avec le massage cardiaque
lehk-ser-sees mon-truh ko-mahn ray-ah-nee-may ah-vek luh mah-sazh kar-dee-ak

A few helpful notes:

• L’exercice: the x sounds like ks
• montre: the final e is not strongly pronounced
• comment here means how, and the -ent is not pronounced like English ent
• réanimer has a clear é sound at the start
• cardiaque ends roughly like dee-ak

As usual, the real French sounds are smoother than English spelling can show, but this should help you get close.