Я взял лёгкие гантели, потому что после работы мне не хотелось поднимать тяжёлую штангу.

Взял is the perfective past tense of взять (to take). It presents the action as a completed whole:
I took the light dumbbells.

If you used брал (from брать, imperfective), it would sound more like:

• I was taking
• I used to take
• or it might focus on the process rather than the completed choice

In this sentence, the speaker means they chose/took the dumbbells on that occasion, so взял fits best.

Also, взял is masculine singular past tense, so it tells us the speaker is male. A female speaker would say взяла.

Because лёгкие agrees with гантели in:

• number: plural
• gender: plural form
• case: accusative plural

Гантели is plural, so the adjective must also be plural:

• лёгкая гантель = a light dumbbell
• лёгкие гантели = light dumbbells

Since гантели are inanimate, the accusative plural looks the same as the nominative plural, so лёгкие гантели stays the same here.

Because the sentence means dumbbells in the plural, not a dumbbell.

• гантель = dumbbell (singular)
• гантели = dumbbells (plural)

In context, this sounds natural because people often think of dumbbells as a pair or as a set of lighter weights, while штанга is a single barbell.

Because штангу is the direct object of поднимать (to lift), so it goes into the accusative case.

Штанга is a feminine singular noun, so in the accusative singular:

• тяжёлая штанга = a heavy barbell (nominative)
• тяжёлую штангу = a heavy barbell (accusative)

The adjective must match the noun, so both words change:

• тяжёлая → тяжёлую
• штанга → штангу

Because после (after) requires the genitive case.

So:

• работа = work (nominative)
• после работы = after work (genitive)

This is a very common pattern:

• после урока = after the lesson
• после фильма = after the movie
• после тренировки = after the workout

So после работы simply means after work.

Потому что is one of the most common ways to say because.

So:

• Я взял лёгкие гантели, потому что... = I took the light dumbbells because...

It introduces the reason for the first action.

There are other ways to express cause in Russian, but потому что is the most direct and neutral choice here.

This is a very common Russian pattern.

• я не хотел = I did not want to
• мне не хотелось = I didn’t feel like, I wasn’t in the mood to

So мне не хотелось поднимать тяжёлую штангу is not just about a rational decision. It sounds more like:

• I didn’t feel like lifting a heavy barbell
• I wasn’t up for lifting a heavy barbell

Grammatically, this is an impersonal construction:

• мне = to me (dative)
• не хотелось = it was not wanted / I didn’t feel like

This structure is extremely common in Russian for physical or emotional states:

• мне холодно = I am cold
• мне скучно = I am bored
• мне не спится = I can’t sleep / I don’t feel sleepy

Мне is the dative case of я.

Here it marks the experiencer, the person who feels the state:

• мне не хотелось = I didn’t feel like it
  • literally, something like to me it did not feel wanted

This is different from English, where we usually make I the subject. Russian often uses the dative with impersonal expressions.

This is about aspect.

• поднимать = imperfective
• поднять = perfective

After не хотелось, the imperfective is usually more natural when talking about an activity in general:

• мне не хотелось поднимать тяжёлую штангу = I didn’t feel like lifting a heavy barbell

This focuses on the activity itself, not on one single completed lift.

If you said поднять, it would suggest more of a single completed act:

• I didn’t feel like lifting it up once / managing one lift

So поднимать is the better choice for a general gym-context meaning.

Because хотеться here is used impersonally.

In an impersonal construction, there is no normal grammatical subject like я, so the verb often appears in the neuter singular past form:

• мне хотелось
• мне не хотелось

That is why it is хотелось, not хотел or хотела.

Compare:

• Я не хотел поднимать штангу = I didn’t want to lift the barbell
• Мне не хотелось поднимать штангу = I didn’t feel like lifting the barbell

Yes. Russian word order is fairly flexible, because case endings show the grammatical roles.

The original sentence is neutral and natural:

• Я взял лёгкие гантели, потому что после работы мне не хотелось поднимать тяжёлую штангу.

But other orders are possible for emphasis, for example:

• После работы мне не хотелось поднимать тяжёлую штангу, поэтому я взял лёгкие гантели.
  • After work, I didn’t feel like lifting a heavy barbell, so I took the light dumbbells.

You can move parts around, but the original version sounds very normal.

The marks show where the stress falls in pronunciation.

For example:

• лёгкие
• тяжёлую

In normal Russian writing, stress marks are usually not written, except in dictionaries, textbooks, or learner materials.

Also, ё is important:

• лёгкие has ё, which always carries stress
• Many printed texts replace ё with е, but for learners it is helpful to keep ё

Yes. The contrast helps make the sentence feel natural:

• лёгкие гантели = lighter, easier weights
• тяжёлая штанга = a heavy barbell, something more demanding

So the sentence implies:

• after work, the speaker lacked energy
• therefore they chose an easier form of exercise

This contrast is both grammatical and stylistic: it makes the reason very clear.