ちから, たわめる and を-Particle

Question

I stumbled upon a sentence where I don't get the grammar:

(括れは) 柔{やわ}らかなままに弾{はず}んだ力{ちから}をたわめていて

the topic being the waist of a woman.

What I don't understand shouldn't it rather be で instead of を (because the waist is bent with a springyness or elasticity)?

Or is it a case where で and を can be used equivalently similar like in this post here: Making sense of transitive usage of 行く and 来る - 「を行く」 and 「を来る」 ?

In my opinion it would be the waist that should be an object to たわめる.

BTW: is たわめる the potential form of たわむ? because my dictionary has two different entries for たわめる - one potential form of "to bend/たわむ" and the other "to bend (a piece of wood)" which is not potential. Is there any real difference?

Thanks a lot!

Answer 1

Grammatically speaking, たわめる is a simple transitive verb, くびれ is its subject, and 弾んだ力 is its object. (を before an intransitive verb is also a kind of location marker like English "across" or "through", but that has nothing to do with this sentence.)

Dictionaries say たわめる is a transitive verb meaning "to bend (something)", although "to bend a force" makes little sense. Actually, たわめる is a more nuanced verb. It's used with an elastic sheet- or stick-like object (e.g., bow, bamboo, rubber mat), and implies the existence of a restoring force. Bending a steel pipe using a burner is パイプを曲げる but not パイプをたわめる because the deformation is irreversible. So, although 力をたわめる is perhaps not a standard combination, I think it means "to hold/store a (spring-like, elastic) force" here. 柔らかなままに弾んだ力をたわめていて is basically describing how her waist is "soft yet bouncy".

Answer 2

is たわめる the potential form of たわむ?

No, たわむ doesn't have the potential form because it's a non-volitional intransitive verb, besides, the subject for たわむ is virtually limited to inanimate objects, which can't be the subject for potential verbs, like your example.

たわめる is the transitive version of たわむ. In this case, 捩じれ is the subject to bend something and 弾んだ力 is the object to be bended.