Learn Hardcore German: Im Fitnessstudio trainiert sie so konzentriert, dass sie alles um sich herum vergisst. - At the gym she trains so focused that she forgets everything around her.

German main clauses follow the verb‑second rule (V2): the conjugated verb must be the second element in the sentence, no matter what comes first.

Element 1: Im Fitnessstudio (a prepositional phrase, “at the gym”)
Element 2: trainiert (the conjugated verb)
Then comes the subject: sie

You cannot put the subject directly after the first phrase if that would push the verb out of second position, so *Im Fitnessstudio sie trainiert is ungrammatical.

You could also say:

Sie trainiert im Fitnessstudio so konzentriert, dass …

Here, sie is element 1 and trainiert is still element 2.

Why is there a comma before dass, and why does vergisst go at the very end?

dass introduces a subordinate clause (“that …”). In German:

A comma is mandatory before most subordinate conjunctions, including dass.
In subordinate clauses, the conjugated verb goes to the end of the clause.

The subordinate clause here is:

dass sie alles um sich herum vergisst

Word order inside it:

Subject: sie
Object: alles um sich herum
Conjugated verb at the end: vergisst

If you made it a main clause, you’d say:

Sie vergisst alles um sich herum.

But with dass, it becomes subordinate, and vergisst moves to the end.

What exactly does the structure so konzentriert, dass … mean?

The pattern so + adjective/adverb + dass expresses a degree that leads to a result:

so konzentriert, dass …
= “so focused that …” / “so concentrated that …”
= “to such an extent that …”

So the sentence means: in the gym she trains to such a high level of concentration that the result is: she forgets everything around her.

This is very similar in function to English “so … that …”.

Is konzentriert an adjective or an adverb here, and why doesn’t it get an ending like konzentrierte?

Here konzentriert functions as an adverb-like predicate, describing how she trains:

sie trainiert konzentriert = “she trains in a focused way”

In German, when adjectives are used:

before a noun, they take endings:
- ein konzentriertes Training (“a focused training session”)
after a verb like sein, bleiben, wirken, arbeiten, trainieren, they are predicative and do not take endings:
- sie ist konzentriert
- sie arbeitet konzentriert
- sie trainiert konzentriert

So no ending is needed: konzentriert stays in its basic form.

What exactly is im, and why is that form used with Fitnessstudio?

im is the contracted form of in dem:

in dem Fitnessstudio → im Fitnessstudio

Fitnessstudio is neuter: das Fitnessstudio.
With in you choose the case based on meaning:

in
- dative for location (Where?):
  - im Fitnessstudio = “in/at the gym”
in
- accusative for movement towards (Where to?):
  - ins Fitnessstudio (in + das) = “into the gym”

Because the sentence describes where she trains (a location, not a movement), dative is used, so in dem → im.

Why is it alles um sich herum, not alles um sie herum?

sich is the reflexive pronoun for the 3rd person (singular and plural). It refers back to the subject sie (she).

sie vergisst alles um sich herum
= she forgets everything around herself

If you said alles um sie herum, it would usually mean:

she forgets everything around another woman / them / that person,
not necessarily herself. It points to someone else, not reflexively back to the subject.

Also, the preposition um always takes the accusative case, and sich is the accusative reflexive form for 3rd person.

What does herum add to um sich herum, and can you leave it out?

The combination um … herum literally means “around … (on all sides)” and is very idiomatic.

alles um sie herum = everything around her (on all sides, in her surroundings)

You can sometimes see um sie without herum, but:

um sie herum is much more natural when talking about things surrounding a person,
herum strengthens the idea of being surrounded.

In this fixed-type phrase alles um sich herum (vergessen), leaving out herum would sound incomplete or unusual.

Why is the present tense trainiert used, when in English we might say “she is training”?

German generally does not have a separate progressive form like English “is training”. The Präsens (present tense) covers both:

sie trainiert = “she trains” or “she is training”

Context decides whether it’s a habitual action or something happening right now. In this sentence, it can easily be understood as a situation that happens when she trains at the gym, possibly repeatedly.

Is trainiert here a present tense form or a past participle? Both look the same.

trainiert can indeed be:

3rd person singular present of trainieren:
- sie trainiert = “she trains / she is training”
past participle:
- sie hat trainiert = “she has trained”

In this sentence, trainiert is definitely the finite present-tense verb, because:

It appears in second position in a main clause: Im Fitnessstudio trainiert sie …
There is no auxiliary like hat or ist, which you’d need for a participle.

Only the conjugated verb (finite verb) can occupy that V2 (2nd position) slot.

Could you also say Sie trainiert im Fitnessstudio so konzentriert, dass …? Does it change the meaning?

Yes, this is also correct:

Sie trainiert im Fitnessstudio so konzentriert, dass sie alles um sich herum vergisst.

The meaning is essentially the same. The difference is focus:

Im Fitnessstudio trainiert sie …
→ slightly more emphasis on the place (at the gym).
Sie trainiert im Fitnessstudio …
→ more neutral; first you mention she, then where she trains.

In both versions, the grammar (V2 rule, so … dass construction, subordinate clause word order) works in the same way.