Learn Hardcore Finnish: Hän pitää itsensä kunnossa juoksemalla puistossa joka toinen päivä. - She/He keeps herself/himself in shape by running in the park every other day.

pitää + sta/stä → to like
- Pidän kahvista. = I like coffee.
pitää + objektin akkusatiivi/genetiivi → to keep, to hold
- Hän pitää oven auki. = He/She keeps the door open.

In Hän pitää itsensä kunnossa…, the structure is:

pitää + itsensä + kunnossa = to keep oneself in shape / in good condition.

So here pitää means “to keep”, not “to like”.

Why is it itsensä and not itseään?

Both forms come from itse (“self”), but they are different cases:

itsensä = genitive/accusative form (a total object)
itseään = partitive form (a partial/ongoing object)

In this sentence, pitää itsensä kunnossa describes the whole person being kept in good condition as a kind of stable result:

Hän pitää itsensä kunnossa.
= He/She keeps himself/herself in shape. (the whole self)

If you used itseään, it would sound like a continuous, unbounded process focused on the action rather than a stable “kept in shape” result. With pitää kunnossa, Finnish strongly prefers the total object:

pitää jonkun/jonkin kunnossa → typically genitive/accusative, so itsensä is natural and idiomatic here.

What exactly is itsensä? Is it a reflexive pronoun?

Yes. Itsensä is the usual third-person reflexive pronoun form in structures like “himself / herself / itself”.

Morphologically:

itse = “self”
itse + nsä (possessive suffix for 3rd person) → itsensä

In meaning:

Hän pitää itsensä kunnossa.
= He/She keeps himself/herself in shape.

If you said:

Hän pitää hänet kunnossa.
that would mean: He/She keeps him (another person) in shape.

So itsensä tells us that the object is the same person as the subject (reflexive).

What form is kunnossa, and why not kuntoon?

The base noun is kunto = condition, fitness, shape.

Common forms:

kunnossa = inessive (in-), “in condition / in shape”
kuntoon = illative (into-), “into condition / into shape”
kunnon = genitive, often “proper / real / good (quality)”

In the sentence:

pitää itsensä kunnossa = “keep oneself in shape (in good condition)”

If you used kuntoon, it would mean:

saada itsensä kuntoon = “to get oneself into shape” (change of state, reaching shape)

Here the idea is maintaining an already good condition, so kunnossa (“in shape”) fits perfectly.

What is juoksemalla, and how does it work grammatically?

Juoksemalla is the third infinitive in the instructive case of the verb juosta (“to run”).

Pattern:

Verb: juosta
3rd infinitive stem: juokse-
Instructive ending: -malla / -mällä

→ juoksemalla = “by running”

Its main use is to express means or manner, roughly “by doing X”:

Hän pitää itsensä kunnossa juoksemalla…
= He/She keeps himself/herself in shape by running…

Other examples:

Opin suomea lukemalla. = I learn Finnish by reading.
Hän laihtui syömällä vähemmän. = He/She lost weight by eating less.

So there is no separate word for “by” – -malla / -mällä plays that role.

Why is there no preposition like “by” before juoksemalla?

Finnish usually uses case endings instead of prepositions.

In English:

by running, with a car, in the park

In Finnish, those become mostly one word with an ending:

juoksemalla = by running (-malla)
autolla = by car (-lla)
puistossa = in the park (-ssa)

So juoksemalla already contains the “by” meaning – adding a separate preposition would be ungrammatical.

What does puistossa mean exactly, and why that form?

Puisto = park.

Puistossa is the inessive case of puisto:

puistossa = “in the park”

So:

juoksemalla puistossa = “by running in the park”.

Other related forms:

puistoon = into the park
puistosta = out of/from the park

How should I understand joka toinen päivä? Does it mean “every day” or “every other day”?

Joka toinen päivä literally:

joka = every
toinen = second, (an)other
päivä = day

Together, it means “every other day” / “every second day”.

Compare:

joka päivä = every day
joka toinen päivä = every other day
joka kolmas päivä = every third day

So the sentence means they run in the park every other day, not daily.

Is the word order fixed? Could I move joka toinen päivä or puistossa?

Finnish word order is relatively flexible, especially for adverbials (time, place, manner), though the neutral order here is:

Hän pitää itsensä kunnossa juoksemalla puistossa joka toinen päivä.

You could say, for example:

Hän pitää itsensä kunnossa juoksemalla joka toinen päivä puistossa.
Joka toinen päivä hän pitää itsensä kunnossa juoksemalla puistossa.

The basic meaning stays the same. Changes in order usually affect emphasis or flow, not core meaning, as long as the sentence remains clear.

What you generally would not do is split juoksemalla puistossa in a confusing way, like:

✗ Hän pitää itsensä kunnossa puistossa juoksemalla joka toinen päivä.
(still possible, but sounds less smooth; “puistossa” usually feels more tightly connected to the running)

How would this sentence change if I wanted to say “He/She got himself/herself into shape by running in the park every other day”?

You’d need:

Past tense of pitää or preferably another verb for “get into shape”.
kuntoon instead of kunnossa to show a change of state (“into shape”).

Two natural options:

Using saada itsensä kuntoon (“get oneself into shape”):
- Hän sai itsensä kuntoon juoksemalla puistossa joka toinen päivä.
Using pitää in the past, but that usually suggests maintaining shape, not getting into it:
- Hän piti itsensä kunnossa juoksemalla puistossa joka toinen päivä.
  = He/She kept himself/herself in shape…

So for “got into shape”, sai itsensä kuntoon is more precise than just changing the tense of pitää.