Я сделал двадцать приседаний и десять отжиманий перед бегом.

Сделал is the perfective past form of сделать, so it presents the action as completed: the speaker finished doing the squats and push-ups.

• Я сделал двадцать приседаний... = I did / completed twenty squats...
• Я делал приседания... would sound more like I was doing squats or I used to do squats, with the focus on the process rather than the completed result.

In this sentence, the speaker is talking about a finished set of exercises before another action, so сделал is the natural choice.

In the past tense, Russian verbs agree with the speaker's gender.

• сделал = masculine
• сделала = feminine
• сделало = neuter
• сделали = plural

So this sentence assumes the speaker is male. If a woman says it, she would say:

Я сделала двадцать приседаний и десять отжиманий перед бегом.

Because after numbers like 5, 6, 7... 20, 21? actually the pattern depends on the final number.

Here we have:

• двадцать приседаний
• десять отжиманий

After 5 and higher (including 10 and 20), the noun is usually in the genitive plural.

So:

• пять приседаний
• десять отжиманий
• двадцать приседаний

That is why you see приседаний and отжиманий, not the dictionary forms приседания and отжимания.

Russian number phrases are one of the trickier grammar areas. A useful basic pattern is:

• 1 → noun in singular:
  один присед
• 2, 3, 4 → noun in a special counting form that looks like genitive singular:
  два приседания, три отжимания
• 5 and higher → noun in genitive plural:
  пять приседаний, десять отжиманий

So in your sentence:

• двадцать приседаний
• десять отжиманий

both use the genitive plural.

Also note:

• 21 приседание
• 22 приседания
• 25 приседаний

The last digit matters, except for the teens (11–14), which always take the 5+ pattern.

Because the preposition перед requires the instrumental case.

The noun бег becomes бегом in the instrumental:

• бег = running / run
• перед бегом = before running / before the run

This is a normal preposition-case pattern in Russian:

• перед сном = before sleep
• перед уроком = before class
• перед тренировкой = before training

So перед бегом is grammatically required.

It can mean either, depending on context.

Russian often uses a noun where English might use either:

• a noun phrase: before the run
• or a gerund-like phrase: before running

So перед бегом can be understood as:

• before going for a run
• before the run
• before running

In everyday Russian, this is very natural.

Yes, до бега is possible, but перед бегом is usually more natural here.

The difference is roughly:

• перед бегом = before the run / immediately before running
• до бега = before the run, but often a bit more abstract or less tied to the immediate moment

For exercise routines, перед бегом sounds especially natural because it suggests the squats and push-ups happened as part of the warm-up or preparation right before the run.

Because Russian, like English, can use one verb for two coordinated objects when the same action applies to both.

So:

Я сделал двадцать приседаний и десять отжиманий...

means:

I did twenty squats and ten push-ups...

You could repeat the verb, but it would usually be unnecessary:

Я сделал двадцать приседаний и сделал десять отжиманий...

This is grammatical, but less smooth unless you want special emphasis.

Yes, it is natural.

In Russian, common verbs with exercises include:

• делать / сделать приседания
• делать / сделать отжимания
• делать / сделать упражнения

The perfective сделать is especially common when talking about a completed number of repetitions:

• Я сделал 30 отжиманий.
• Она сделала 50 приседаний.

So this sentence sounds normal and idiomatic.

Because with countable exercise nouns such as приседания and отжимания, Russian usually just gives the number plus the noun.

So:

• двадцать приседаний = twenty squats
• десять отжиманий = ten push-ups

You do not need раз here.

The word раз is used more for counting occurrences of an action in a broader sense:

• Я прочитал это три раза. = I read this three times.
• Я ходил туда два раза. = I went there twice.

But for exercise repetitions, the noun itself usually carries the meaning clearly.

Their dictionary forms are:

• приседание = squat
• отжимание = push-up

Both are neuter nouns ending in -ие / -ание.

In the sentence, they appear in the genitive plural:

• приседание → приседаний
• отжимание → отжиманий

This is the form required after двадцать and десять.

Yes. Russian word order is more flexible than English word order.

The neutral order here is:

Я сделал двадцать приседаний и десять отжиманий перед бегом.

But you could also say:

• Перед бегом я сделал двадцать приседаний и десять отжиманий.
• Двадцать приседаний и десять отжиманий я сделал перед бегом.

These all mean basically the same thing, but the emphasis changes:

• Перед бегом... puts the time/context first.
• Двадцать приседаний и десять отжиманий... emphasizes the exercises/counts.

The original version is very natural and straightforward.

No. Although сделать is often related to to do / to make, the best English translation depends on context.

Here:

• Я сделал двадцать приседаний = I did twenty squats

Other examples:

• Я сделал ошибку = I made a mistake
• Я сделал домашнее задание = I did my homework
• Я сделал стол = I made a table

So you should translate сделал by meaning, not word-for-word the same way every time.