Learn French: C'est à nous de maintenir l'apnée pendant l'enchaînement. - It is up to us to maintain the breath-holding during the sequence.

Yes! The structure C'est à + stress pronoun + de + infinitive is used to express either a turn or a responsibility. Depending on the context, it translates to 'It is up to us to' (duty) or 'It is our turn to' (turn). Here, maintaining breath-holding is clearly a duty during a physical activity.

Why do we use the preposition de before maintenir?

In this specific expression, de acts as the mandatory bridge connecting the phrase C'est à nous (It is up to us) with the action we are supposed to do. Whenever you use C'est à [someone] to introduce an action, you must follow it with de + infinitive.

Does l'apnée refer to the medical condition 'sleep apnea' here?

Not in this context. While it does mean 'apnea' medically, in everyday French and sports, l'apnée simply refers to breath-holding. For example, freediving is commonly called la plongée en apnée.

What kind of 'sequence' is l'enchaînement?

The word comes from the verb enchaîner (to link or chain together). Un enchaînement is a continuous sequence of linked movements flowing smoothly from one to the next. You will frequently hear this vocabulary used in swimming, yoga, martial arts, or gymnastics.