A musculação usa o aparelho de musculação.

Portuguese often uses the definite article with general nouns more freely than English does.

So a musculação can mean weight training in a general sense, not necessarily the weight training in a very specific context.

This is normal in Portuguese:

• A musculação faz bem. = Weight training is good.
• A natação ajuda muito. = Swimming helps a lot.

English usually drops the article in these broad, general statements, but Portuguese often keeps it.

Musculação usually refers to weight training, strength training, or working out with weights/machines.

Depending on context, it can overlap with bodybuilding, but it is often broader and more everyday than English bodybuilding.

For example:

• Eu faço musculação. = I do weight training / I lift weights.
• Academia de musculação = a gym focused on weight training

So in many learning contexts, weight training is the safest translation.

Usa is the third-person singular form of the verb usar in the present indicative.

From usar:

• eu uso = I use
• você/ele/ela usa = you/he/she uses
• nós usamos = we use
• eles/elas usam = they use

In this sentence, the subject is a musculação, which is singular, so the verb is usa.

Because it is describing two different nouns:

1. a musculação
   Here, musculação is the main noun itself.

2. o aparelho de musculação
   Here, de musculação describes what kind of aparelho it is: a weight-training machine/device.

So the repetition is grammatical, even if it sounds a little repetitive in style.

It is similar to saying:

• Weight training uses a weight-training machine.

That is understandable, but stylistically a bit repetitive.

Aparelho is a broad word. It can mean:

• device
• apparatus
• machine
• equipment
• sometimes appliance, depending on context

In a gym context, aparelho de musculação usually means a weight machine or exercise machine.

So here aparelho is not just any device; it means a gym machine used for strength training.

O aparelho means the machine/device, while um aparelho means a machine/device.

Using o suggests a more specific or generic-known item:

• o aparelho de musculação = the weight machine / the exercise machine

Using um would sound less specific:

• um aparelho de musculação = a weight machine

Both are grammatically possible, but they do not mean exactly the same thing.

It is grammatical, but it sounds a bit unusual and repetitive.

Native speakers would more naturally say something like:

• Na musculação, usa-se aparelho de musculação.
• A musculação usa aparelhos.
• Na musculação, usam-se aparelhos.
• A musculação é feita com aparelhos.

Why does the original sound a little odd? Because musculação and aparelho de musculação repeat the same idea, so the sentence feels heavy.

So the sentence is useful for learning vocabulary and grammar, but it is not the most natural everyday phrasing.

Yes, in real life, people often use multiple machines, so aparelhos in the plural might sound more natural in many contexts.

Compare:

• o aparelho de musculação = the weight machine
• os aparelhos de musculação = the weight machines / gym machines

If you are speaking generally, plural is often more natural:

• Na musculação, usam-se aparelhos de musculação.

But singular is still grammatically correct if the idea is generic or if one machine is being referred to as a type.

Yes, grammatically it can be the subject.

Portuguese, like English, can let an activity or field act as the subject:

• A medicina usa tecnologia moderna. = Medicine uses modern technology.
• A educação usa métodos diferentes. = Education uses different methods.

So A musculação usa... is grammatically fine.

The issue is not grammar; it is mainly style. In everyday speech, many people would prefer a more impersonal structure, such as:

• Na musculação, usa-se...

Both can refer to gym machines, but there is a slight nuance:

• aparelho is broader and very common in Brazilian Portuguese for gym equipment
• máquina is also common and can sound a bit more specifically like a machine

In a gym, Brazilians often say things like:

• os aparelhos da academia = the gym machines/equipment
• essa máquina = that machine

So both are possible, but aparelho is a very common word in fitness contexts.

Yes, Portuguese allows some flexibility, although not every version sounds equally natural.

Original:

• A musculação usa o aparelho de musculação.

Possible alternatives:

• Na musculação, usa-se o aparelho de musculação.
• O aparelho de musculação é usado na musculação.

These alternatives shift the focus:

• the first focuses on the activity/context
• the second focuses on the machine

So word order can change, but the most natural choice depends on what you want to emphasize.

Because de is directly followed by musculação, and musculação does not have an article here.

Contractions happen when a preposition combines with an article:

• de + o = do
• de + a = da

Examples:

• o aparelho do professor
• a porta da academia

But here it is just:

• aparelho de musculação

That is a normal noun phrase meaning weight-training machine.

Yes — and that is extremely common.

In fact, fazer musculação is one of the most common ways to talk about doing weight training:

• Eu faço musculação três vezes por semana. = I do weight training three times a week.

So while the sentence you were given uses musculação as the subject, learners should also know this very common pattern:

• fazer musculação = to do weight training