в качестве vs. как

[wolfie-18.livejournal.com]

So I wrote the following sentence as such

"Один олимпийский спортсмен, как тренировка, переплыл через пролив."

And the teacher corrected the "как тренировка" part to "в качестве тренировки." When to use what?

Comments

[oryx_and_crake]

как тренировка does not work in your case. It might work in the following case: Бег трусцой очень эффективен как тренировка выносливости. "как тренировка" is referring to the subject, so you have to ensure that the subject of your sentence is the activity itself. In your original sentence you actually said: спортсмен, как тренировка... which does not make sense because an athlete is not a training.

[dvanoltri.livejournal.com]

And you shouldn't place commas if you use "как" as "в качестве".

[archaicos.livejournal.com]

Another way to say it ... спортсмен для тренеровки переплыл...
You can't say спортсмен как тренеровка, because a human being isn't a practice/workout/whatever, you can't compare them or define one through the other which is what you tried to do with the original sentence.
These are OK though:
Машина, как средство передвижения, очень удобна. The car as a means of transportation is very convenient.
Регулярные упражнения, такие как тренировка, укрепляют организм. Regular exercises such as a workout strengthen the body.
The punctuation may be flawed.

[oryx_and_crake]

please mind your spelling: тренИровка

[archaicos.livejournal.com]

I'm so deeply embarrassed. I mean it.

[oryx_and_crake]

also такие, как needs a comma
but
машина как средство передвижения does not need any

[o-jovem-louco.livejournal.com]

The sentence that you had written could be translated like this:
A certain Olympic sportsman has crossed the channel like a training.
If you don't put there a comma you'll get something like this:
A certain Olympic sportsman has crossed the channel as a means of a training.
That sportsman neither looks like a training nor works as a training, got it? ;)