Learn Hardcore Finnish: Juoksen niin kovaa, että alan hikoilla heti. - I run so fast that I start to sweat immediately.

So niin strengthens kovaa (“so hard/fast”), and että introduces the result clause. The pair niin ... että belongs together; että alone would not have the same “so … that” meaning here without niin (or something similar) in the main clause.

Is niin really necessary? What happens if you leave it out?

In this kind of result sentence, niin is practically required.

✔ Juoksen niin kovaa, että alan hikoilla heti.
✖ Juoksen kovaa, että alan hikoilla heti. (sounds wrong/unfinished)

Without niin, the connection “so … that …” is broken. You could rephrase in other ways (for example, using koska or joten), but for this exact pattern of degree + result, niin ... että functions as a unit and you normally keep both parts.

What exactly is kovaa, and why isn’t it nopeasti or kovasti?

Kovaa is the partitive form of the adjective kova (hard), used adverbially. Finnish often forms adverbs from adjectives in two ways:

-sti adverbs:
- nopea → nopeasti (fast → quickly)
Partitive -a/-ä adverbs:
- kova → kovaa (here: hard, intensely, fast)

With juosta (to run), juosta kovaa is a very natural, everyday way to say “run fast / run really hard”. It emphasizes intensity or effort as well as speed.

nopeasti = quickly, fast in a more neutral, speed-focused way
kovaa = hard, intensely, (really) fast; often more colloquial and vivid
kovasti exists, but it usually means a lot, very much, strongly, and is not the usual adverb with juosta for speed

So Juoksen niin kovaa sounds very natural and idiomatic, a bit like “I run so hard/so fast” in everyday speech.

Why is the verb juoksen and not something like minä juoksen? Where did the pronoun go?

Finnish usually drops subject pronouns when the verb ending already shows the person:

juokse-n = I run
juokse-t = you run
juokse-e = he/she runs

Because -n on juoksen already tells you it’s 1st person singular, the pronoun minä is not needed:

Juoksen niin kovaa, että alan hikoilla heti. = I run so fast that I start to sweat immediately.

You can say Minä juoksen... for emphasis (for example, to contrast me with someone else), but the neutral form normally omits minä.

Why is there a comma before että?

In Finnish, a comma is normally placed before a subordinate clause introduced by conjunctions like että, koska, jotta, etc.

Here:

Main clause: Juoksen niin kovaa
Subordinate (result) clause: että alan hikoilla heti

The comma marks the boundary between them:

Juoksen niin kovaa, että alan hikoilla heti.

Leaving out the comma would be considered a punctuation error in standard written Finnish.

What does alan hikoilla mean exactly, and why is hikoilla in this infinitive form?

Alan hikoilla literally means “I begin to sweat” / “I start sweating.”

alan = I start / I begin (1st person singular of alkaa)
hikoilla = infinitive form of hikoilla (to sweat)

Verbs like alkaa (to begin), ruveta (to start), lakata (to stop) are commonly followed by the basic infinitive (the so‑called A‑infinitive):

alan juosta – I start to run
alan hikoilla – I start to sweat
lakkasin puhumasta – I stopped talking (here another infinitive form is used)

If you changed hikoilla to a finite form (hikoilen), the meaning would change:

että alan hikoilla heti = that I start to sweat immediately
että hikoilen heti = that I sweat immediately (no “start”, just the action)

Could you also say alan hikoilemaan instead of alan hikoilla?

You will definitely hear alan hikoilemaan in spoken Finnish, but there are some points to note:

alan hikoilla – uses the basic (A‑)infinitive; this is standard and fully correct.
alan hikoilemaan – uses the MA‑infinitive; this combination with alkaa is very common in speech, but many style guides treat it as non‑standard when written (they prefer alkaa + A‑infinitive).

So:

In formal or careful written Finnish, alan hikoilla is the recommended form.
In everyday spoken Finnish, alan hikoilemaan is widely used and understood.

Why is heti placed at the end? Could it go somewhere else?

Heti means “immediately / right away.” In this sentence it modifies alan hikoilla:

että alan hikoilla heti = that I start to sweat immediately

In Finnish, adverbs like heti are quite flexible in position, but the placement affects emphasis slightly:

että alan hikoilla heti – neutral, very natural
että heti alan hikoilla – puts a bit more emphasis on immediacy
Heti alan hikoilla, kun juoksen niin kovaa. – heti is emphasized and moved to the beginning of its clause

In the original sentence, heti at the end is the most straightforward way to say “immediately.”

Could I change the word order, for example: Alan hikoilla heti, koska juoksen niin kovaa?

Yes, that sentence is grammatical, but the structure and nuance change:

Juoksen niin kovaa, että alan hikoilla heti.
- Pattern: niin ... että (so ... that) ⇒ directly expresses degree + result.
Alan hikoilla heti, koska juoksen niin kovaa.
- Pattern: koska (because) ⇒ gives a reason rather than a pure result construction.

Both can describe the same real‑world situation, but:

niin ... että focuses on the extent of the first clause leading to a result.
koska focuses more on a cause–effect explanation.

Word order between the two clauses is flexible; you can also say:

Koska juoksen niin kovaa, alan hikoilla heti.

Can että here be understood as “so that”, like a purpose (in order that)?

In this sentence, että is not expressing purpose, but result.

Juoksen niin kovaa, että alan hikoilla heti.
→ I run to such a degree that the result is: I start to sweat.

“Purpose” (in order that) would normally be used with jotta:

Juoksen kovaa, jotta ehtisin ajoissa.
= I run fast so that I would make it on time (in order to be on time).

So:

niin ... että → result / consequence (so ... that ... happens)
jotta → purpose (so that / in order that)

Is it possible to say Juoksen niin nopeasti, että alan hikoilla heti instead of niin kovaa? Does it sound different?

Yes, you can say:

Juoksen niin nopeasti, että alan hikoilla heti.

It is grammatically correct and means almost the same thing. The nuance:

niin kovaa – colloquial, vivid, emphasizes effort/intensity (I’m really going at it).
niin nopeasti – slightly more neutral, emphasizes speed itself.

Both are natural. Niin kovaa is very typical in everyday speech when talking about running or similar physical effort.