Das Duschen nach dem Sport macht mich wach.

Because Duschen is being used as a noun, not as a normal verb.

• duschen = to shower
• das Duschen = showering / the act of showering

In German, nouns are capitalized, so Duschen gets a capital D.

This is called a nominalized verb: a verb turned into a noun.

Because the sentence needs a subject, and here the subject is the act of showering.

• duschen by itself is the infinitive verb: to shower
• das Duschen turns that verb into a noun phrase: showering

So:

• Duschen nach dem Sport macht mich wach can sometimes be heard, but
• Das Duschen nach dem Sport macht mich wach is the more standard and complete version

The article das is very common with these noun-like infinitives.

They are related, but not the same.

• das Duschen = showering, the activity
• die Dusche = the shower, usually the shower itself or a shower as a countable event

So this sentence uses das Duschen because it is talking about the activity of showering, not the shower as an object.

Compare:

• Das Duschen nach dem Sport macht mich wach.
  = Showering after exercise makes me feel awake.

• Die Dusche nach dem Sport macht mich wach.
  = The shower after exercise makes me feel awake.

The second one is possible too, but it focuses more on the shower as a specific thing/event, while das Duschen emphasizes the activity itself.

Because nach takes the dative case here.

Sport is masculine in German: der Sport.

So the forms are:

• nominative: der Sport
• dative: dem Sport

That is why you get:

• nach dem Sport = after sport / after exercise

This is a very important pattern:

• nach dem Essen = after the meal / after eating
• nach der Arbeit = after work
• nach dem Unterricht = after class

Here, nach means after in a time sense.

So nach dem Sport means after exercising or after sports.

Be careful: nach has several meanings in German, for example:

• after: nach dem Sport
• to with some places: nach Berlin
• according to: nach dem Lehrer

In this sentence, it is clearly the time meaning: after.

Because machen in this structure takes an accusative object.

The pattern is:

etwas macht jemanden + adjective

= something makes someone something / makes someone feel a certain way

So:

• macht mich wach = makes me awake
• mich is accusative
• mir would be dative, and that does not fit this pattern

More examples:

• Kaffee macht mich nervös. = Coffee makes me nervous.
• Musik macht ihn glücklich. = Music makes him happy.
• Das Wetter macht uns müde. = The weather makes us tired.

Wach is an adjective meaning awake.

In this sentence, it is used predicatively, which means it comes after the verb and describes the object mich.

That is why it has no adjective ending.

Compare:

• ein wacher Mann = an awake man
  Here, wacher has an ending because it comes before a noun.

• Ich bin wach. = I am awake.
  No ending.

• Das Duschen macht mich wach. = Showering makes me awake.
  Also no ending.

So wach is not acting like an adverb here; it is an adjective describing me.

Because German main clauses normally follow the verb-second rule.

The finite verb must be in the second position.

Here, the first position is taken by the whole subject:

Das Duschen nach dem Sport

Then comes the finite verb:

macht

Then the rest:

mich wach

So the structure is:

[Das Duschen nach dem Sport] [macht] [mich wach].

Even though the subject is several words long, it still counts as one unit in first position.

Yes, absolutely.

That version is also grammatical. German allows you to move elements around for emphasis, as long as the finite verb stays in second position.

Compare:

• Das Duschen nach dem Sport macht mich wach.
  Focuses naturally on showering after exercise as the topic.

• Nach dem Sport macht mich das Duschen wach.
  Puts more emphasis on after exercise.

Both mean essentially the same thing.

Not necessarily. In everyday German, Sport often means exercise, working out, or physical activity in general, not only organized sports.

So nach dem Sport can mean:

• after working out
• after exercise
• after playing sports

This is broader than English sport sometimes sounds.

Yes. Even if the meaning is already known, it is useful to know that the German sentence can match several natural English versions, depending on context:

• Showering after exercise wakes me up.
• A shower after working out makes me feel awake.
• Showering after sports makes me feel more awake.

This is because macht mich wach is literally makes me awake, but in natural English we often say wakes me up or makes me feel awake.