Learn Russian: Спортивная обувь очень важна для тренировок. - Sports shoes are very important for workouts.

In Russian, обувь translates closer to footwear and is a collective noun. It is always grammatically singular. Because of this, the matching adjective спортивная is also in the singular form.

How do we know the gender of обувь since it ends in a soft sign?

Nouns ending in a soft sign can be either masculine or feminine, so you just have to memorize them. You can tell обувь is feminine in this sentence because the adjectives describing it, спортивная and важна, both use feminine endings.

Why does the sentence use важна instead of the regular adjective важная?

Важна is a short-form adjective. Russian often uses short forms instead of full adjectives when stating a fact or quality as the main point of the sentence (acting as the verb "is"). Since обувь is feminine singular, we use the feminine short form важна.

Why does тренировок end in -ок?

The preposition для (for) requires the Genitive case. The base word is тренировка (workout). In the Genitive plural, feminine nouns ending in -а drop that letter. To make the resulting word easier to pronounce, an о is inserted between the final two consonants, changing it to тренировок.