Minha rotina mudou quando eu passei a fazer exercício antes do trabalho.

Because rotina is a feminine noun in Portuguese.

Possessive words must agree with the noun they describe:

• meu = my, for masculine singular nouns
• minha = my, for feminine singular nouns

So:

• meu trabalho = my job/work
• minha rotina = my routine

Mudou is the third-person singular preterite form of mudar.

The subject is minha rotina, which is grammatically third-person singular, so the verb must match it:

• minha rotina mudou = my routine changed

The preterite is used here because it refers to a change seen as a completed event or turning point in the past.

Quando means when and introduces the time when something happened.

In this sentence:

• Minha rotina mudou = My routine changed
• quando eu passei a fazer exercício... = when I started doing exercise...

So quando connects the main event with the moment that caused or accompanied the change.

Passei a fazer means I started to do or I began doing.

This comes from the structure:

• passar a + infinitive

It often means that someone began a new habit, behavior, or state.

Examples:

• Passei a estudar mais. = I started studying more.
• Ela passou a trabalhar de casa. = She started working from home.

So in your sentence, eu passei a fazer exercício means I started exercising.

Because passar has many meanings, and here it is part of the expression passar a + infinitive.

On its own, passar can mean things like:

• to pass
• to go by
• to spend time
• to hand something over

But in passar a fazer, it has a special meaning: to begin to do something.

So you should understand passei a fazer as a unit, not word by word.

Yes, it could be omitted.

Portuguese often leaves out subject pronouns when the verb form already makes the subject clear:

• quando eu passei a fazer exercício
• quando passei a fazer exercício

Both are natural.

Including eu can add:

• clarity
• emphasis
• contrast

So the speaker may include it simply for style or emphasis, but it is not strictly necessary here.

In Brazilian Portuguese, fazer exercício in the singular is very common when talking about exercise in general.

It works a lot like saying:

• to exercise
• to do exercise

You can also hear fazer exercícios, but that often sounds more like:

• doing exercises
• doing specific workout movements or practice activities

So:

• fazer exercício = exercise as a general activity
• fazer exercícios = do exercises, often more specific or countable

Yes.

Common alternatives in Brazilian Portuguese include:

• fazer exercício = neutral, very common
• me exercitar = to exercise, a bit more formal or explicit
• malhar = to work out, common in everyday Brazilian Portuguese, especially for gym exercise

Examples:

• Passei a me exercitar antes do trabalho.
• Passei a malhar antes do trabalho.

Each is natural, but fazer exercício is a very safe, general option.

Because do is the contraction of:

• de + o = do

The expression is:

• antes de = before

When de is followed by the masculine singular article o, they contract:

• antes de o trabalho → antes do trabalho

So:

• antes do trabalho = before work / before the job / before work starts

Portuguese uses articles more often than English does.

So even where English says:

• before work

Portuguese often says:

• antes do trabalho

This is very natural in Brazilian Portuguese. A direct word-for-word match with English is not always possible here.

It can suggest either, depending on context.

Trabalho can mean:

• work as an activity
• job as employment
• workplace/work schedule, depending on the situation

In this sentence, antes do trabalho most naturally means before going to work or before starting work.

Because the expression is antes de, not antes a.

So the structure is:

• antes de + noun
• antes de + infinitive

Examples:

• antes do almoço = before lunch
• antes da aula = before class
• antes de sair = before leaving

That is why the sentence uses antes do trabalho.

Passei is the first-person singular preterite of passar.

So:

• eu passei = I passed / I started / I went through, depending on context

Here, because of passar a + infinitive, it means:

• I started

The preterite fits well because it marks the beginning of a new habit at a point in the past.

Because passei a fazer emphasizes the moment or fact that the new habit began.

• passei a fazer = I started doing
• passava a fazer would be unusual here and would not normally express the same clear completed shift

The sentence is about a change in routine, so the preterite passei works better than the imperfect.

Yes, that is also correct.

• começar a + infinitive = to start to do something
• passar a + infinitive = to begin doing something, often with the idea of adopting a new habit or state

Both are natural, but passar a fazer can sound especially good when talking about a lifestyle change or a new routine.

This is a very normal Portuguese sentence structure:

• Minha rotina = subject
• mudou = main verb
• quando... = time clause explaining when the change happened
• antes do trabalho = time expression inside that clause

A more literal breakdown is:

• My routine changed
• when I started exercising
• before work

The order is natural and clear in Portuguese.

The accent in exercício shows the stressed syllable:

• e-xer-CÍ-cio

It also tells you that the word does not follow the default stress pattern.

So the accent helps both with:

• pronunciation
• correct spelling

Without the accent, the spelling would be wrong.

Rotina usually means routine, especially daily habits or a regular pattern of life.

Depending on context, it can refer to:

• daily routine
• schedule
• usual way of doing things

In this sentence, it means the person’s daily routine / lifestyle pattern changed.