Is the word músculos the same in Brazilian and European Portuguese?

Yes

The word "músculos" is identical in spelling, meaning, and grammatical classification (masculine plural noun) in both Brazilian and Continental Portuguese. The only difference lies in pronunciation.

In Brazilian Portuguese, the vowels are generally more "open" and clearly articulated, and the rhythm of the word is more melodic. In Continental Portuguese, unstressed vowels tend to be "reduced" or "closed"; the "u" and the "o" may sound much shorter or more muffled, giving the word a more clipped, rhythmic, and "closed" sound.

Brazilian Portuguese Examples

1. Eu treinei muito e agora meus músculos estão doendo. (I trained a lot and now my muscles are hurting.)
2. Ele tem músculos muito definidos. (He has very defined muscles.)
3. Você precisa comer proteína para ganhar músculos. (You need to eat protein to gain muscle.)
4. Sinto uma dor forte nos músculos das costas. (I feel a strong pain in my back muscles.)
5. O exercício ajuda a fortalecer os músculos do abdômen. (The exercise helps to strengthen the abdominal muscles.)

Continental Portuguese Examples

1. Eu treinei muito e agora os meus músculos estão a doer. (I trained a lot and now my muscles are hurting.)
2. Ele tem músculos muito definidos. (He has very defined muscles.)
3. É preciso comer proteína para ganhar massa muscular. (It is necessary to eat protein to gain muscle mass.)
4. Sinto uma dor forte nos músculos das costas. (I feel a strong pain in my back muscles.)
5. O exercício ajuda a fortalecer os músculos abdominais. (The exercise helps to strengthen the abdominal muscles.)