What is the main action with がてら (in the given example)?

Question

The grammar dictionary どんなときどう使う日本語表現文型辞典 defines がてら in the following way:

1. Accomplishing two objectives via one action. Can also mean to produce two results by doing a single action.
2. Verbs of movement, such as 歩くor 行く, often follow.

It also gives the following example:

② 散歩がてら、ちょっと郵便局まで行ってきます。

The sentence ② is basically consistent with the example given in this question, and the explanation given in the answer: "the phrase 散歩がてら立ち寄った公園 would make more sense because stopping at a park is done while on the walk."

It is also consistent with the explanation given in this answer: "運転(し)がてら食事する -- eating along the way driving (after having driven half way)"

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Now, the problem is that the same dictionary gives also another example:

④ 駅まで３０分ほどかかるが、天気のいい日は　運動がてら歩くこと　にしている。

and I see it as contrary to the above.

Walking is neither done in the middle of an exercise; nor is exercising the main action here (as we are talking about the station, then the action of moving towards the station should be, no matter what).

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Why isn't the example written in the following way:

駅まで３０分ほどかかるが、天気のいい日は　歩くことがてら運動　にしている。

Would there be a difference in meaning? What would be the meaning then?

^{Even if, for some reason, it doesn't sound right for a native speaker, please explain what meaning it would convey.}

Does it matter that the predicate is making decision (にする) here?

Answer 1

According to 明鏡国語辞典, 「～がてら」 can mean either 「～のついでに」 or 「～を兼ねて」.

And it gives two examples:

A: 「駅に行きがてら郵便局に立ち寄る」
B: 「散歩がてら買い物に行く」

The がてら in A means のついでに. I think the one in B can be interpreted as either のついでに or を兼ねて.

A: "I drop by at the post office along the way to the station."
B: "I go shopping while taking a walk." OR "I go shopping and it also/partly serves as a walk."

So I think your sentences:

② 散歩がてら、ちょっと郵便局まで行ってきます。
④ 駅まで３０分ほどかかるが、天気のいい日は運動がてら歩くことにしている。

The がてら in ② can be either 「を兼ねて」 "partly for the purpose of~~" "which also serves as~~" or 「のついでに」 "while doing~~" "along the way".　The one in ④ is used in the sense of 「を兼ねて」.

「駅まで３０分ほどかかるが、天気のいい日は（駅まで）歩きがてら運動することにしている」

I think it would mean "I (regularly/usually) get some exercise while walking to the station." (but it doesn't sound very natural to me...)

Answer 2

"運動がてら歩くことにしている" is OK but I prefer 歩きがてら運動することにしている.

歩くことがてら is simply ungrammatical and 運動することにしている means "I am scheduled (at my own will) to exercise myself" while 運動にしている means "I make it into exercise".

Answer 3

散歩がてら、ちょっと郵便局まで行ってきます。

駅まで３０分ほどかかるが、天気のいい日は　運動がてら歩くこと　にしている。

It's a kind of long walk that it takes 30 min to the station, but it makes a good exercise, so the speaker chooses to walk when the weather is good. The speaker is talking about walking to the station. The がてら phrase is an adverbial phrase; the sentence stands without it.

If it's 駅まで３０分ほどかかるが、天気のいい日は歩きがてら運動することにしている, it's talking about the exercise done by the long walk. Here I find the adverbial phrase is something more important than a mere modifier; you can't omit 歩きがてら.