Learn French: Est-il agile pendant le dressage sans les rênes ! - How agile he is during the dressage without the reins!

This is a stylistic exclamative inversion, which is the focus of this lesson. Instead of using an exclamative word like comme or que (as in Comme il est agile !), literary or formal French can simply invert the subject pronoun and verb to express 'How [adjective] he is!'. The exclamation mark is your visual clue that it is an exclamation rather than a question.

How would this sentence look if I wanted to use a noun like ce cheval (this horse) instead of the pronoun il?

You would use complex inversion. Just like in formal questions, you state the noun first, then invert the corresponding pronoun: Ce cheval est-il agile pendant le dressage ! You cannot put the noun directly into the inverted position (so Est ce cheval agile ! would be incorrect).

Is dressage used exactly the same way in French as it is in English?

It is similar, but the French meaning is broader. While English 'dressage' almost exclusively refers to the equestrian sport, the French word dressage refers to the training or taming of any animal (like dogs or wild animals). In this sentence, the phrase sans les rênes (without the reins) provides the context that we are indeed talking about a horse.

Why do we need the article le in pendant le dressage when English just says 'during dressage'?

French almost always requires a determiner (like le, la, or les) before a noun, especially for abstract concepts, sports, or activities. While English often drops the article for general activities ('during training', 'during dressage'), French keeps it, which is a great rule to remember when translating your thoughts directly from English.