Learn Hardcore Swahili: Baada ya kukimbia, tunahisi jasho likitoka na misuli ikichoka. - After running, we feel sweat coming out and our muscles getting tired.

baada ya + ku-verb = after doing X
- baada ya kula – after eating
- baada ya kuoga – after bathing
- baada ya kukimbia – after running

This infinitive acts like an English -ing noun (running, eating), so baada ya kukimbia is like saying “after (the) running” or “after running”, not “after we ran”.
If you really want a full clause with tense and subject, you would use baada ya plus kufanya or another structure, but for everyday speech baada ya + ku-verb is the standard and most natural way.

What does tunahisi literally mean, and how is it different from tunajisikia or tunajihisi?

tunahisi = we feel / we sense
tunajisikia / tunajihisi = we feel (ourselves), often about physical or emotional state

In practice:

tunahisi jasho likitoka = we feel (that) sweat is coming out
– here jasho is the object of hisi.
tunajisikia vibaya = we feel bad / unwell (about ourselves)
tunajihisi wachovu = we feel (ourselves to be) tired

In the sentence you gave, tunahisi jasho likitoka is natural because you’re feeling something external (the sweat), not just describing your internal general state.

Why is it jasho likitoka and not jasho linatoka?

Both are grammatically correct, but they do slightly different things:

jasho linatoka = the sweat is coming out (simple present/progressive statement)
jasho likitoka = as (the) sweat comes out / while the sweat is coming out

The -ki- in likitoka acts like a “when / as / while” marker. It often corresponds to English “-ing” in subordinate clauses:

Nilitembea jua likiwaka. – I walked while the sun was shining.
Tunazungumza mvua ikinyesha. – We are talking as it rains.

So tunahisi jasho likitoka carries the nuance “we feel (it), as the sweat comes out”, more like an ongoing accompaniment than a simple fact.

Why is the subject prefix li- used in likitoka with jasho?

Swahili verbs agree with the noun class of their subject. Jasho (sweat) is in noun class 5 (often labeled JI-/LI-):

Class 5 singular subject prefix: li-
Class 5 plural noun (if used): majasho with subject prefix ya-

So:

jasho linatoka or jasho likitoka – the sweat is coming out / as the sweat comes out.

The li- doesn’t indicate tense here; it’s just subject agreement with the noun jasho.

Why is the subject prefix i- used in misuli ikichoka?

Misuli (muscles) is the plural of msuli and behaves like a class 4 noun in this context:

Class 3 singular (m-/mw-) often uses u- as subject prefix
Class 4 plural (mi-) uses i- as subject prefix

So:

msuli umechoka – the muscle is tired
misuli imechoka – the muscles are tired
misuli ikichoka – as the muscles get tired / as the muscles are getting tired

Again, i- is just subject agreement with misuli.

What exactly is the role of -ki- in likitoka and ikichoka? Is it a tense?

-ki- here is not a normal tense like present or past; it is a converb / subordinator that often means “when / while / as”.

Pattern:

[main clause], [subject prefix] + ki + verb root ...

Examples:

Nilisoma muziki ukiendelea. – I studied while the music was continuing / playing.
Watoto walicheza mvua ikinyesha. – The children played as it was raining.

So in your sentence:

jasho likitoka – as sweat comes out
misuli ikichoka – as the muscles get tired

They express actions that happen at the same time as the feeling described by tunahisi.

Why is na used between jasho likitoka and misuli ikichoka? Could we omit it?

Here na functions as “and”, joining two parallel things you feel:

jasho likitoka – sweat coming out
misuli ikichoka – muscles getting tired

So:

tunahisi jasho likitoka na misuli ikichoka
= we feel sweat coming out and (we feel) muscles getting tired.

You normally keep the na; without it, you’d have two phrases next to each other that sound incomplete or run-on. The na clearly signals two separate but related experiences.

Could we say Baada ya kukimbia, tunahisi jasho linatoka na misuli inachoka instead? How would that change the meaning?

Yes, that is grammatically fine:

jasho linatoka – the sweat is coming out
misuli inachoka – the muscles are getting tired

Compared to likitoka / ikichoka:

linatoka / inachoka: simple present/progressive; more like plain statements.
likitoka / ikichoka: with -ki-, sound more like ongoing accompanying actions, similar to English “as it comes out / as they get tired”.

So your version is more neutral and straightforward; the original version adds a slight “as this is happening” nuance.

Why do we use baada ya instead of just baada or kwa baada ya?

Baada ya is a fixed prepositional phrase in Swahili meaning “after”:

baada ya kazi – after work
baada ya chakula – after the meal
baada ya kukimbia – after running

You don’t normally say:

✗ baada kukimbia
✗ kwa baada ya kukimbia

The structure is simply:

baada ya + noun / noun-like thing (including ku-verb)

So ya is part of this fixed expression and also matches baada, which is treated like a class 9 noun taking ya.

Could we replace Baada ya kukimbia with Tukimaliza kukimbia or Tukiisha kukimbia? Are they equivalent?

They are close in meaning, but not identical:

Baada ya kukimbia – after running (more neutral, time reference)
Tukimaliza kukimbia – when we finish running / once we finish running
Tukiisha kukimbia – when we have finished running / once we’re done running

All can introduce what happens after the running, but:

baada ya kukimbia focuses simply on time sequence.
tukimaliza / tukiisha kukimbia emphasize completion of the activity (“when we finish / when we’re done”).

Your original sentence is slightly more general and stylistically simpler.

Why is there a comma after Baada ya kukimbia? Is it required in Swahili?

Punctuation in Swahili generally follows similar conventions to English. A comma after Baada ya kukimbia:

marks a natural pause,
separates the time expression from the main clause.

You could technically write it without a comma in informal contexts and many people do, but:

Baada ya kukimbia, tunahisi ...

is the recommended, clearer style, especially in writing or teaching materials.