Learn Hardcore Swedish: Den som har en regelbunden vana att träna får lättare positiv energi. - The one who has a regular habit of exercising gets positive energy more easily.

So Den som har en regelbunden vana att träna… = “The one who has a regular habit of exercising…” / “Whoever has a regular habit of exercising…”

You cannot say Den har en regelbunden vana… for “whoever has…”.
Den har… would literally be “That one has…”, referring to a specific thing/person already known, not to people in general.

This den som construction is very common in Swedish to talk about people in a general way:

Den som pluggar mycket klarar provet.
Whoever studies a lot passes the test.

Is den som singular or plural here? Could we say de som instead?

Grammatically, den som is singular (“the one who”). It focuses more on the individual person, in a general sense.

You can also say:

De som har en regelbunden vana att träna får lättare positiv energi.
= Those who have a regular habit of exercising get positive energy more easily.

de som is plural (“those who”). Both versions are correct; the difference is nuance:

Den som … = “the (any) individual who …”
De som … = “all those people who …”

Both are common in Swedish when making general statements.

What exactly is the role of som in den som har en regelbunden vana att träna?

Here som is a relative pronoun, like English who / that.

den = the one
som har en regelbunden vana att träna = who has a regular habit of exercising

So the structure is:

Den + som + clause
The one + who + clause

som introduces a relative clause describing den.
This pattern is very productive in Swedish:

Den som kommer först får börja.
The one who comes first gets to start.
Den som vill kan följa med.
Anyone who wants to can come along.

Why say en regelbunden vana att träna instead of simply tränar regelbundet?

Both are possible, but they focus slightly different things.

Den som tränar regelbundet…
= The one who exercises regularly…
Focus: the action itself is regular.
Den som har en regelbunden vana att träna…
= The one who has a regular habit of exercising…
Focus: having a habit (a stable, established routine).

en regelbunden vana att träna sounds a bit more formal and abstract; it emphasizes that training is part of your lifestyle or routine, not just something you happen to do regularly at the moment.

Very natural, simpler alternatives would be:

Den som tränar regelbundet får lättare positiv energi.
Den som har för vana att träna får lättare positiv energi.
(has a habit of exercising)

What does vana mean here, and how is it different from brukar or är van vid?

vana (noun) = habit, custom, practice.

In the sentence:

en regelbunden vana = a regular habit

Compare:

vana (noun)
- Jag har en vana att läsa på kvällen.
  I have a habit of reading in the evening.
bruka (verb, usually in present: brukar)
- Jag brukar läsa på kvällen.
  I usually read in the evening.
  Focus: what you normally do, typical behaviour.
vara van vid (adjective phrase)
- Jag är van vid att läsa på kvällen.
  I am used to reading in the evening.
  Focus: what you are accustomed to; it doesn’t necessarily say how often you currently do it.

So in en regelbunden vana att träna, vana emphasizes a stable, repeated habit, not just occasional training.

Why is there att before träna? Could we leave it out?

att here is the infinitive marker, like English to in to train.

att träna = to train / to exercise

After vana you normally use att + infinitive:

en vana att läsa – a habit of reading
min vana att träna – my habit of exercising

You cannot drop att in this position in standard Swedish.
So:

✅ en vana att träna
❌ en vana träna (wrong)

Why is the adjective regelbunden in that form, and how would it change in plural or definite form?

regelbunden is the indefinite singular common-gender form of the adjective regelbunden (“regular”).

It agrees with vana, which is:

gender: common (en-word)
number: singular
definiteness: indefinite

So we get:

en regelbunden vana
(one regular habit)

Other forms:

Plural (any gender): regelbundna
- regelbundna vanor – regular habits
Definite singular common: den regelbundna vanan
- den regelbundna vanan – the regular habit
Definite plural: de regelbundna vanorna – the regular habits

Adjective pattern:

Indefinite en-word: regelbunden
Indefinite ett-word: usually regelbundet (e.g. ett regelbundet schema)
Plural / definite: regelbundna

What does får mean here, and why not har or another verb?

In this sentence, får = “gets / obtains / receives”.

får lättare positiv energi
= gets positive energy more easily

Using other verbs would change the meaning:

har positiv energi = has positive energy (state, not about getting it)
blir mer positiv = becomes more positive (talks more about mood/personality change)

få is the natural verb for “to get / to receive” both concrete and abstract things:

få en present – get a present
få idéer – get ideas
få energi – get (gain) energy

What exactly does lättare mean here? Is it “lighter”, “easier”, or something else, and easier than what?

lättare is the comparative of lätt and here it means “more easily”.

lätt = easy / easily
lättare = easier / more easily

In this context, it is best understood as:

får lättare positiv energi
= gets positive energy more easily

The comparison is implied:

either compared to people who do not train regularly, or
compared to the same person when they didn’t have this habit.

Swedish often uses a comparative without saying explicitly than what when it is obvious from context.

It does not mean “lighter energy” here; it’s about how easily you get it, not about how heavy anything is.

Why is lättare placed before positiv energi and not at the end, like får positiv energi lättare?

Both word orders are possible, but they sound slightly different:

får lättare positiv energi (most natural here)
Focus: how easily you get something; lättare is close to the verb.
får positiv energi lättare
Also grammatical, but sounds a bit more marked; you might be specifically contrasting with some other way of getting positive energy.

In Swedish, adverbs like lätt / lättare commonly appear:

before the object (here: positiv energi), or
at the end of the predicate.

Examples:

Vi får ofta besök. – We often get visitors.
Vi får besök ofta. – Also possible, but the tone/flow changes.

In this sentence, får lättare positiv energi is the smooth, neutral choice.

Why is there no article before positiv energi? Why not den positiva energin or en positiv energi?

energi is usually treated as an uncountable, abstract noun in this kind of context. In Swedish, such nouns often appear without an article when used in a general sense:

får positiv energi – gets positive energy (in general)
känner glädje – feels joy
ger stöd – gives support

If you say:

den positiva energin = the positive energy
You now talk about some specific, known positive energy.
en positiv energi = a positive energy
Sounds unusual here; it suggests one kind of positive energy, or is used in certain stylistic/philosophical contexts, but not as a neutral general statement.

So positiv energi without article is the natural, generic way to express the idea of “positive energy”.

Could the whole sentence be phrased more simply or more commonly in Swedish? If so, how?

Yes. While the original sentence is correct, a couple of simpler and very natural versions are:

Den som tränar regelbundet får lättare positiv energi.
Whoever trains regularly gets positive energy more easily.
De som tränar regelbundet får lättare positiv energi.
Those who train regularly get positive energy more easily.
Slight variation with “usually”:
- Den som brukar träna regelbundet får lättare positiv energi.

The version with tränar regelbundet is more straightforward than har en regelbunden vana att träna, and is extremely common in everyday Swedish.