Learn Hardcore French: La natation est moins fatigante pour mon dos que la course à pied. - Swimming is less tiring for my back than running.

La natation is a noun: it means “swimming” as a sport/activity (like “swimming” vs “swim” or “swimming (as a sport)” in English).
- La natation est moins fatigante… = Swimming (the sport) is less tiring…
Nager is a verb (the infinitive): “to swim”.
You could say:
- Nager est moins fatigant pour mon dos que courir.
  = Swimming is less tiring for my back than running.

Using the noun (la natation) makes it sound more like you’re talking about the sport in general, the same way you’d say “La course à pied” for running (as a sport).

Why is it fatigante (with an e) and not fatigant?

Adjectives agree with the noun they describe in gender and number.

La natation is feminine singular → the adjective must be feminine singular:
- fatigant → masculine singular
- fatigante → feminine singular
- fatigants → masculine plural
- fatigantes → feminine plural

So:

La natation est fatigante. ✅ (feminine singular)
Le marathon est fatigant. ✅ (masculine singular)
Les compétitions sont fatigantes. ✅ (feminine plural)

In your sentence, fatigante agrees with la natation.

What’s the difference between fatigant(e) and fatigué(e)?

They’re related but not the same:

fatigant / fatigante = tiring (causing fatigue)
- La natation est moins fatigante.
  = Swimming is less tiring.
fatigué / fatiguée = tired (the state of a person/animal)
- Je suis fatigué.
  = I’m tired.

So:

La course à pied est fatigante.
= Running is tiring.
Je suis fatigué après la course à pied.
= I’m tired after running.

About spelling: in modern usage, the adjective is normally fatigant / fatigante (without u). You may also see fatiguant as a present participle of fatiguer, but in sentences like this one, fatigant(e) is standard.

Why do we say moins fatigante pour… que… and not something like moins de fatigante que…?

In French comparatives:

moins + adjective + que
→ to compare qualities.
- moins fatigante que = less tiring than
moins de + noun + que
→ to compare quantities.
- moins de fatigue que = less tiredness than
- moins de travail que = less work than

So:

La natation est moins fatigante que la course à pied. ✅
Swimming is less tiring than running. (quality)
La natation provoque moins de fatigue que la course à pied. ✅
Swimming causes less fatigue than running. (quantity)

“moins de fatigante” is ungrammatical, because you can’t use moins de directly with an adjective like that.

Could we put the adjective before the noun, like la fatigante natation?

You can put fatigante before natation, but it’s unusual and sounds very literary or emphatic:

la natation fatigante = neutral, normal order
la fatigante natation = very marked style, almost poetic or complaining

In everyday French, most adjectives of physical effect, opinion, etc. go after the noun:

un sport fatigant
une activité intéressante
un exercice difficile

So in your sentence, est moins fatigante after la natation is the normal, natural word order.

Why is it pour mon dos and not pour le dos or à mon dos?

pour mon dos
- Means “for my back / on my back / as far as my back is concerned”.
- We use mon because we clearly want to say whose back it is.
- Very natural here:
  - C’est bon pour mon dos. = It’s good for my back.
pour le dos
- Means “for the back” in general, without specifying whose.
- You could say:
  - La natation est bonne pour le dos.
    = Swimming is good for the back (in general).
à mon dos
- This is not idiomatic in this context.
- à with body parts is used in fixed expressions like avoir mal au dos (“to have a backache”), but not to mean “for my back”.

So in your exact meaning (“for my back”), pour mon dos is the best choice.

But don’t the French usually say le dos for body parts, not mon dos?

Very often, yes — especially with reflexive verbs:

Je me suis cassé le dos.
= I broke my back.
Il se lave les mains.
= He’s washing his hands.

However, after pour, it’s more natural to use the possessive if you want to highlight whose body part it is:

C’est mauvais pour tes yeux.
C’est bon pour mon cœur.
C’est moins fatigant pour mon dos.

You can say pour le dos when you’re speaking in general (neutral, medical advice style). But if the point is your back specifically, mon dos is the natural choice.

Is dos masculine or feminine, and how can I tell from this sentence?

Dos is masculine: le dos.

In the sentence, you can see that from mon:

mon = masculine singular (or any singular noun starting with a vowel sound)
ma = feminine singular (before a consonant sound)
mes = plural

Because it’s mon dos and not ma dos, you know dos is masculine.

What exactly does la course à pied mean? Why not just la course or courir?

La course à pied is a set expression meaning “running (on foot), running as a sport”.

course alone just means “race / running / run” in a broad sense:
- une course = a race
- faire des courses = to go shopping / run errands (different meaning!)

To avoid ambiguity and to refer clearly to running as a sport, French usually says:

la course à pied
faire de la course à pied = to go running

Compare:

La natation est moins fatigante pour mon dos que la course à pied. ✅
Swimming is less tiring for my back than running (as a sport).

You could also use:

courir (verb):
- Nager est moins fatigant pour mon dos que courir.
le jogging (informal, more like “jogging”):
- La natation est moins fatigante pour mon dos que le jogging.

Why do we say la natation and la course à pied with “la” if we’re speaking in general?

French often uses the definite article (le, la, les) to talk about activities, sports, or things in a general sense:

J’aime la natation. = I like swimming (in general).
Le sport est bon pour la santé. = Sport is good for your health.
La musique classique est populaire ici. = Classical music is popular here.

Similarly:

La natation est moins fatigante…
…que la course à pied.

We’re talking about these sports in general, not one specific swimming session or one specific run, so French uses la.

If you were talking about doing the sport, you’d use de la:

Je fais de la natation. = I swim / I do swimming.
Je fais de la course à pied. = I (go) run(ning).

Could I move pour mon dos and say La natation est moins fatigante que la course à pied pour mon dos?

Yes, that’s grammatically correct:

La natation est moins fatigante pour mon dos que la course à pied.
La natation est moins fatigante que la course à pied pour mon dos.

Both are possible. The meaning is basically the same, but:

Putting pour mon dos earlier keeps it closer to moins fatigante, underlining “less tiring on my back”.
Putting it at the end is also fine; some speakers might find the original version slightly smoother.

You could also, more formally or emphatically, insert commas:

La natation est, pour mon dos, moins fatigante que la course à pied.
(Very correct, a bit more written/formal.)

Could I say C’est moins fatigant pour mon dos de nager que de courir instead? How is that different?

Yes, that’s a very natural alternative:

C’est moins fatigant pour mon dos de nager que de courir.

Differences:

Subject of the sentence
- Original: La natation is the grammatical subject.
- New version: C’ (empty “it”) is the subject, and the real content comes with de nager… de courir.
Style
- La natation est moins fatigante…
  → slightly more formal, more like a written or descriptive style.
- C’est moins fatigant pour mon dos de nager que de courir.
  → very natural, spoken-style, close to English “It’s less tiring for my back to swim than to run.”

Both are correct; they just use different structures to express the same idea.