Learn Hardcore Finnish: Nämä lenkkikengät ovat kevyet, joten juoksu tuntuu helpolta. - These running shoes are light, so running feels easy.

Ostan kevyitä kenkiä. – I buy light shoes. (object in the partitive)
Pöydällä on kevyitä kenkiä. – There are some light shoes on the table. (an indefinite “some”)

With a clear, definite plural subject like nämä lenkkikengät, the normal predicative form is nominative plural kevyet, not kevyitä.

Why is the verb ovat and not on?

In standard Finnish, the verb olla (to be) agrees in number with the subject:

Nämä lenkkikengät ovat kevyet.
nämä lenkkikengät = they → ovat (3rd person plural)

Using on here would be considered colloquial:

Spoken: Nämä lenkkikengät on kevyet.

You also see on with a plural noun in existential sentences, where the subject comes after the verb:

Pöydällä on lenkkikenkiä. – There are running shoes on the table.

But in your sentence, nämä lenkkikengät is a normal plural subject in front of the verb, so written/standard Finnish uses ovat.

Why are lenkkikengät in the plural?

This is the same as in English shoes:

One shoe: lenkkikenkä (singular)
A pair / both shoes together: lenkkikengät (plural)

You almost always refer to them as a pair, so the plural is the default:

Missä mun lenkkikengät ovat? – Where are my running shoes?

You’d typically only use the singular lenkkikenkä if you literally mean one shoe (e.g. “I lost one shoe”).

How is lenkkikengät formed, and what’s the nuance compared with lenkkarit or juoksukengät?

Lenkkikengät is a compound word:

lenkki = a jog, a run (for exercise)
kenkä = shoe

Singular: lenkkikenkä → plural nominative: lenkkikengät
(kenkä → kengät shows normal consonant gradation: kenkä : kengät)

Nuances:

lenkkikengät – neutral, often a bit more formal; “running/jogging shoes, trainers”.
lenkkarit – very common colloquial word for sneakers/trainers.
Plural: lenkkarit; singular (rare): lenkkari.
juoksukengät – specifically running shoes, often for more serious running.

In your sentence, lenkkikengät is neutral and completely natural.

Why is it Nämä lenkkikengät and not Ne lenkkikengät?

Both are possible, but they’re used a bit differently:

nämä = these (here, near me)
ne = those / they (often more distant or already known from context)

Typical uses:

When you’re pointing at shoes right next to you:
Nämä lenkkikengät ovat kevyet. – These running shoes are light.
When both speaker and listener already know which shoes you’re talking about (or they’re not physically near):
Ne lenkkikengät ovat kevyet. – Those / those particular running shoes are light.

In a teaching example, nämä is nice and concrete: “these shoes (here)”.

Why is juoksu (a noun) used here instead of a verb like juosta or the -minen form juokseminen?

In Finnish you often use a noun to talk about an activity in general:

juoksu = running (as a sport/activity)

So:

juoksu tuntuu helpolta
≈ “running feels easy” (literally, “the running feels easy”).

You cannot say:

*juosta tuntuu helpolta – incorrect

because tuntua takes a noun or -minen form as its subject, not an infinitive.

Juokseminen tuntuu helpolta is also correct:

juokseminen = the act of running
This can sound a bit more “nominalized” or formal; juoksu is often shorter and more natural in everyday speech here.

So both:

Juoksu tuntuu helpolta.
Juokseminen tuntuu helpolta.

are grammatically okay, with a small nuance difference. Your sentence just chooses the simpler juoksu.

Why is it juoksu tuntuu (singular verb), not tuntuvat?

In the second clause, the subject is juoksu, which is singular, so the verb is also singular:

juoksu tuntuu helpolta – running feels easy.

Earlier, in Nämä lenkkikengät ovat kevyet, the subject is plural (lenkkikengät), so we use ovat.

So you see:

plural subject → ovat
singular subject → tuntuu

Why is it helpolta instead of helppo?

This is a key pattern with tuntua:

tuntua + adjective in the ablative case (-lta / -ltä)

It means “feel (like) X”:

juoksu tuntuu helpolta – running feels easy
Se kuulostaa hyvältä. – That sounds good.
Keitto maistuu pahalta. – The soup tastes bad.

Formally:

Adjective: helppo (easy)
Stem: help(o)- (weak grade, p instead of pp)
Ablative ending: -lta
→ helpolta

Compare:

Nämä kengät ovat helpot. – These shoes are easy (to put on / to use).
(with olla, the adjective is in the nominative: helpot)
Nämä kengät tuntuvat helpoilta. – These shoes feel easy (to use).
(with tuntua, it’s ablative: helpuilta in plural, helpolta in singular)

Can I say Nämä lenkkikengät ovat kevyitä instead of kevyet?

In this sentence, kevyet is the natural and expected choice.

With a definite plural subject (like nämä lenkkikengät = these particular shoes), the predicative adjective normally appears in nominative plural:
Nämä lenkkikengät ovat kevyet.

The partitive plural (kevyitä) is used in other situations, e.g.:

Pöydällä on kevyitä kenkiä. – There are some light shoes on the table.
(indefinite quantity, existential sentence)
Ostan kevyitä kenkiä. – I buy light shoes.

Saying Nämä lenkkikengät ovat kevyitä would sound odd or incorrect in standard Finnish in this context. Stick to kevyet here.

What exactly does joten mean, and can I replace it with siksi?

Joten is a conjunction meaning “so, therefore”:

Nämä lenkkikengät ovat kevyet, joten juoksu tuntuu helpolta.
= These running shoes are light, so running feels easy.

Siksi means “for that reason” and works more like an adverb. It usually starts a new clause or sentence:

Nämä lenkkikengät ovat kevyet, siksi juoksu tuntuu helpolta.
→ These running shoes are light, for that reason running feels easy.

Both are grammatically possible, but:

joten more tightly connects the two clauses into a single sentence.
siksi slightly emphasizes the cause–effect relationship (“for that reason”).

In many contexts they’re close in meaning, but they’re not interchangeable in all word orders or registers. Here, joten is perfectly natural.

Can I change the word order, for example: Juoksu tuntuu helpolta, joten nämä lenkkikengät ovat kevyet?

You can, but it changes the emphasis and logic a bit.

Original:

Nämä lenkkikengät ovat kevyet, joten juoksu tuntuu helpolta.
→ The lightness of the shoes is the cause, the easy feeling of running is the result.

Reversed:

Juoksu tuntuu helpolta, joten nämä lenkkikengät ovat kevyet.
→ “Running feels easy, so (you conclude that) these running shoes are light.”

That second version suggests that from the ease of running you infer that the shoes must be light. Grammatically fine, but a different message.

Inside each clause, the basic word order (Subject – Verb – Complement) is already the neutral order. You could do small variations for emphasis:

Helpolta juoksu tuntuu. – “Easy is how running feels.” (emphasizing easy)

But your original order is the clearest and most neutral.

How would I say “Running feels easy with these running shoes” more explicitly?

You’d make the “with these shoes” part explicit using the adessive case (-lla / -llä):

Näillä lenkkikengillä juokseminen tuntuu helpolta.
Literally: With these running shoes, running feels easy.

Breakdown:

nämä → näillä (adessive plural: on/with these)
lenkkikengät → lenkkikengillä (adessive plural: on/with the running shoes)
juokseminen – the act of running (subject)
tuntuu helpolta – feels easy

You could also say:

Näillä lenkkikengillä juoksu tuntuu helpolta.

Both versions clearly express “with these shoes”; your original sentence just leaves that connection implicit.

Are there any important pronunciation points in juoksu tuntuu helpolta?

Yes, a few:

juoksu:
- Stress on the first syllable: JUO-ksu.
- uo is a diphthong (gliding from u to o in one syllable).
tuntuu:
- Stress on TUN-.
- uu is a long vowel – noticeably longer than a single u. Compare:
  - tuntu (short) vs tuntuu (long).
helpolta:
- Stress on HEL-: HEL-pol-ta.
- The pp of the basic form helppo weakens to p in helpolta (consonant gradation), but you always say only one [p] in helpolta.

Rhythm: every word is stressed on the first syllable, and vowel length is meaningful, so tuntuu must have a clearly long final vowel.