Learn Hardcore Finnish: Hengitystä voi harjoitella yksinkertaisilla harjoituksilla, jotka voitaisiin tehdä vaikka bussissa istuen. - Breathing can be practiced with simple exercises that could be done even while sitting on the bus.

The action is ongoing / repeated / incomplete, or
You’re talking about something as an indefinite amount or process, not as a single, bounded whole.

Here, practising breathing is not about completing one whole, countable “breath”, but about working on the process of breathing in general. That fits the “indefinite, ongoing” idea → partitive.

Compare:

Opiskelen suomea. – I’m studying Finnish. (process, not one “whole” Finnish)
Harjoittelen pianonsoittoa. – I’m practising playing the piano. (process)

If you said hengityksen voi harjoitella, it would sound odd, almost like there is one specific, bounded breathing that you can “finish practising”. So hengitystä is the natural, idiomatic choice.

What does voi harjoitella mean exactly, and why is it not voidaan harjoitella?

Voi harjoitella = “(one) can practise / you can practise / it is possible to practise”.

voi is 3rd person singular of voida (“can, to be able to”).
There is no explicit subject, but Finnish often uses a “generic” 3rd person: (ihminen) voi harjoitella → “a person can practise”, “you can practise”.

So the whole Hengitystä voi harjoitella... is like English “You can practise breathing…” in a general sense.

voidaan harjoitella is the impersonal passive: “breathing can be practised / people can practise breathing”.
You could say:

Hengitystä voidaan harjoitella…

It’s grammatical, but voi harjoitella sounds a bit more direct and colloquial as advice to the reader/listener.

Why is it yksinkertaisilla harjoituksilla and not something like yksinkertaisia harjoituksia?

Yksinkertaisilla harjoituksilla is plural adessive (-lla/-llä) and literally means “with simple exercises” or “by means of simple exercises”.

The adessive here is used in an instrumental sense:
→ “You can practise breathing with simple exercises.”

yksinkertainen harjoitus – a simple exercise
yksinkertaisilla harjoituksilla – with simple exercises

If you said yksinkertaisia harjoituksia, that would just describe “simple exercises” (partitive plural), but you would lose the “with / using” nuance unless you added some other structure:

Hengitystä voi harjoitella tekemällä yksinkertaisia harjoituksia.
“You can practise breathing by doing simple exercises.”

The original sentence just packs that “with/using” idea directly into the adessive case.

Isn’t harjoitella + harjoituksilla repetitive? Do Finns avoid this kind of repetition?

It does look repetitive to an English speaker:

harjoitella – to practise
harjoitus – exercise, practice

But in Finnish this is completely normal and not awkward. The meanings are slightly different:

harjoitella hengitystä – to practise breathing (the activity)
yksinkertaisilla harjoituksilla – with simple exercises (individual tasks)

So it’s more like:

“You can practise breathing with simple exercises…”

This kind of root repetition (verb + related noun) is very common and usually doesn’t feel redundant to Finns.

Why is it jotka and not joka? What is jotka referring to?

Jotka is a relative pronoun (“which/that”) in plural:

joka – which/that (singular)
jotka – which/that (plural)

Relative pronouns in Finnish agree in number with the word they refer to. Here, jotka refers back to harjoituksilla (“exercises”), which is plural:

yksinkertaisilla harjoituksilla → harjoitukset (plural)
jotka → “which (exercises)…”

So:

…yksinkertaisilla harjoituksilla, jotka voitaisiin tehdä…
“…with simple exercises, which could be done…”

If it was just one exercise (yksinkertaisella harjoituksella), you’d say:

…, joka voitaisiin tehdä… – “which could be done…” (singular)

What exactly does voitaisiin mean, and how is it different from voidaan?

Voitaisiin is:

the passive conditional of voida (“can”),
literally: “could be (done)” / “could be able to”.

Breakdown: voi-ta-is-iin

voi – stem from voida
-ta – passive marker
-isi- – conditional
-in – passive ending

So jotka voitaisiin tehdä = “which could be done”.

Difference:

voidaan tehdä – “can be done” (real, neutral possibility)
voitaisiin tehdä – “could be done” (more hypothetical, often more polite or less direct)

In this sentence, voitaisiin makes it sound like:
“These exercises are the kind of thing that one could (for example) do, even while sitting on a bus” – a suggestion rather than a blunt statement of fact.

Could the sentence use voidaan instead of voitaisiin? How would that change the nuance?

Yes, you could say:

Hengitystä voi harjoitella yksinkertaisilla harjoituksilla, jotka voidaan tehdä vaikka bussissa istuen.

This would mean:

“…with simple exercises that can be done even while sitting on a bus.”

Nuance:

voidaan tehdä – straightforward statement: they can be done on the bus.
voitaisiin tehdä – a bit softer: they could be done on the bus (for example; as an option).

So voitaisiin fits well in explanatory, advisory, or slightly tentative language.

What does vaikka mean here? Isn’t it usually “although / even though”?

Vaikka has two common uses:

Concessive: “although / even though”
- Vaikka sataa, menen ulos. – Although it’s raining, I’ll go out.
“Even / for example” with a place/time/way:
- Voit tehdä sen vaikka kotona. – You can do it even at home / for example at home.

In vaikka bussissa istuen, it’s the second use:

vaikka bussissa ≈ “even on a bus”, “for example on the bus”

So it’s emphasising that the exercises are so simple and low‑key that you could even do them while sitting on a bus.

What form is istuen, and what does bussissa istuen literally mean?

Istuen is the third infinitive, instructive case of istua (“to sit”).

It’s often translated as “(while) doing X” or “by doing X”, expressing manner or a simultaneous action.

bussissa istuen literally:

bussissa – “in/on the bus” (inessive case)
istuen – “sitting” (while sitting)

So together: “while sitting on a bus” / “in a sitting position on the bus”.

It describes the situation or posture in which the exercises could be done.

How is istuen different from istumalla or a full clause like kun istuu bussissa?

All three are possible but have slightly different flavours.

istuen (3rd infinitive, instructive)
- Focuses on manner / concurrent state.
- Very compact and quite natural with posture verbs:
  - seisten – standing
  - maaten – lying down
- bussissa istuen – “while sitting on the bus”.
istumalla (3rd infinitive, adessive)
- Often means “by (means of) doing X”, emphasising method.
- bussissa istumalla would sound more like “by sitting on the bus”, which is odd in this context (sitting is not the method of practising).
kun istuu bussissa – “when (one) is sitting on a bus”
- Full finite clause; more explicit, bit heavier style:
- …jotka voitaisiin tehdä, kun istuu bussissa.
  – “…which could be done when (you) are sitting on a bus.”

The original bussissa istuen is short, smooth, and idiomatic for describing a relaxed simultaneous state.

Is the word order bussissa istuen fixed, or could it be istuen bussissa?

Both bussissa istuen and istuen bussissa are grammatically possible.

bussissa istuen slightly highlights the location first:
“(there) on the bus, sitting…”
istuen bussissa slightly highlights the manner/posture first:
“sitting, on the bus…”

In practice, bussissa istuen sounds very natural and smooth here, and that’s probably why it was chosen. The difference is subtle and mostly about rhythm and emphasis, not grammar.

What would be a fairly literal but natural English rendering of the whole sentence?

Literally, keeping the structure fairly close:

“Breathing can be practised with simple exercises, which could be done even while sitting on a bus.”

More idiomatic English might adjust it to:

“You can practise your breathing with simple exercises that you could even do while sitting on the bus.”