Learn Hardcore Turkish: Masaj yaptırdıkça kaslarım güçleniyor. - My muscles get stronger as I get massages.

The suffix -dıkça follows a verb stem to form an adverbial clause expressing a proportional relationship: as one action happens, another action happens to that extent. In masaj yaptırdıkça kaslarım güçleniyor, it literally means as I get massages done, my muscles get stronger.
Additional notes:
• After stems ending in consonants, use -dıkça; after vowel stems, use -dikçe.
• It works with any verb: çalıştıkça (as one works), okudukça (as one reads).

Why is yaptırmak used instead of yapmak? How do these verbs differ?

yapmak = to do something oneself
yaptırmak = causative form of yapmak, meaning to have someone else do something or to get something done
Therefore, masaj yaptırmak means to get a massage, whereas masaj yapmak would mean to give a massage to someone.

Why is there no space between yaptır and -dıkça? Should these not be separate words?

In Turkish, suffixes attach directly to the stem without spacing. Here, yaptır- is the verb stem of yaptırmak, and -dıkça is an affix forming an adverbial clause. Together they form the single word yaptırdıkça.

How is kaslarım constructed? What roles do -lar and -ım play?

kaslarım is built from:
• kas = muscle
• -lar = plural suffix (equivalent to -s in English)
• -ım = 1st person singular possessive suffix (my)
So kas-lar-ım = my muscles. In Turkish, the plural suffix comes before the possessive suffix.

Why is güçleniyor in the present progressive? Could another tense be used?

The suffix -iyor creates the present continuous/progressive tense, which in Turkish also covers habitual actions and general truths. In güçleniyor (is getting stronger), it emphasizes an ongoing or repeated process each time a massage is received.
You could use the simple present (güçlenir) for a general statement, but it doesn’t highlight the ongoing progression. Past (güçlendi) or future (güçlenecek) would shift the focus to completed or anticipated actions.

Why doesn’t masaj take the accusative suffix -ı? Would masajı yaptırdıkça be incorrect?

Turkish marks definite direct objects with the accusative suffix. When an object is indefinite or general, it often appears without the suffix. Here, masaj means a massage (indefinite), so no suffix is needed. If you wanted to refer to a specific massage, you would say masajı yaptırdıkça.

Can I include the pronoun ben in masaj yaptırdıkça? How?

Yes. You can say Ben masaj yaptırdıkça kaslarım güçleniyor. However, Turkish typically omits subject pronouns because the verb endings already indicate person and number.

What is the subject of güçleniyor, and why is kaslarım in the nominative case?

The subject of güçleniyor is kaslarım (my muscles). In Turkish, the nominative case is unmarked—subjects do not take a specific case ending. Instead, kaslarım shows plurality (-lar) and possession (-ım), but no additional case suffix is used to mark it as the subject.