После вчерашних приседаний мои ноги устали, поэтому сегодня я сделал меньше отжиманий.

Because после normally requires the genitive case in Russian.

• после = after
• So the noun that follows it has to be in the genitive.
• приседания is the dictionary form here, but after после it becomes приседаний.

The adjective also has to match the noun in case and number:

• вчерашние приседания = yesterday’s squats
• после вчерашних приседаний = after yesterday’s squats

So both words are in the genitive plural.

Вчерашних is the correct genitive plural form of the adjective вчерашний.

Here is the logic:

• base adjective: вчерашний = yesterday’s
• noun: приседания = squats
• because после requires genitive, the whole phrase changes to genitive plural:
  • вчерашние приседания
  • после вчерашних приседаний

So вчерашних is not random—it is simply the adjective agreeing with a plural noun in the genitive case.

Приседаний is the genitive plural of приседание.

• приседание = a squat
• приседания = squats
• приседаний = of squats / after squats

In this sentence, it is plural because the speaker means a workout involving multiple squats, not just one squat.

Russian very often uses the plural for exercise repetitions:

• 10 приседаний = 10 squats
• после приседаний = after squats

So приседаний is exactly what you expect after после.

Because ноги means legs, and that is plural.

Russian past tense agrees with the subject in number and, in the singular, also in gender.

• нога устала = my leg got tired
• ноги устали = my legs got tired

So:

• мои ноги = my legs
• устали = got tired / became tired, plural form

Since the subject is plural, the verb must also be plural.

Устали comes from the verb устать, which means to become tired / to get tired.

So мои ноги устали means:

• my legs got tired
• or naturally in English, my legs were tired

Russian often prefers a verb like устать where English might use be tired.

Compare:

• ноги устали = the legs got tired / were tired
• ноги были усталыми = the legs were tired

The second version is grammatically possible, but it sounds more descriptive and less natural here. In this sentence, устали is the normal, idiomatic choice.

Поэтому means therefore, that’s why, or so.

It introduces a result:

• После вчерашних приседаний мои ноги устали = After yesterday’s squats, my legs were tired
• поэтому сегодня я сделал меньше отжиманий = so today I did fewer push-ups

The comma is there because Russian separates these two parts as clauses:

• cause: мои ноги устали
• result: поэтому сегодня я сделал меньше отжиманий

So the comma works much like in English before so or therefore.

This is about aspect.

• сделал is perfective
• делал is imperfective

Here, сделал is used because the speaker is talking about a completed result: the total number of push-ups they ended up doing today.

So:

• сегодня я сделал меньше отжиманий = today I did fewer push-ups / I ended up doing fewer push-ups

If you used делал, it would sound more like describing the process, repetition, or activity in progress, not the completed outcome.

In exercise contexts, Russian often uses perfective when talking about how many repetitions someone completed.

In the past tense, Russian verbs agree with the subject in gender if the subject is singular.

So:

• я сделал = I did (male speaker)
• я сделала = I did (female speaker)

In the sentence you were given, сделал tells you the speaker is male.

A female speaker would say:

• После вчерашних приседаний мои ноги устали, поэтому сегодня я сделала меньше отжиманий.

Because меньше usually takes the genitive in Russian when it means less/fewer.

• отжимания = push-ups
• меньше отжиманий = fewer push-ups

This is a very common pattern with words of quantity and comparison:

• много отжиманий = many push-ups
• мало отжиманий = few push-ups
• больше отжиманий = more push-ups
• меньше отжиманий = fewer push-ups

So отжиманий is again a genitive plural form.

Yes, literally сделать often means to make or to do, but in Russian it is also very common with exercises and repetitions.

So Russian naturally says things like:

• сделать 20 отжиманий = do 20 push-ups
• сделать 50 приседаний = do 50 squats

This is just normal usage. English learners sometimes expect one fixed verb like do, but Russian often uses делать / сделать with exercises.

Yes. Russian word order is more flexible than English word order, because case endings show grammatical relationships.

The original sentence is neutral and natural:

• После вчерашних приседаний мои ноги устали, поэтому сегодня я сделал меньше отжиманий.

But other orders are possible, for example:

• Мои ноги устали после вчерашних приседаний, поэтому сегодня я сделал меньше отжиманий.
• Поэтому сегодня я сделал меньше отжиманий could also move slightly depending on emphasis.

The meaning stays basically the same, but the emphasis shifts a little. The original version sounds smooth and standard.

Not exactly.

• вчерашних приседаний means yesterday’s squats
• приседаний вчера would mean something more like squats yesterday, which is much less natural in this kind of phrase

Russian often uses adjectives like вчерашний, сегодняшний, завтрашний to package time neatly into a noun phrase:

• вчерашняя тренировка = yesterday’s workout
• сегодняшняя боль = today’s pain
• завтрашнее занятие = tomorrow’s class

So после вчерашних приседаний is the natural way to say after yesterday’s squats.