Yes, it is OK....not common but grammatically correct. All of your sentences are possible in the right context. Present participles can be used as adverbs. The participle usually follows directly after the verb in that case. Here are a few other examples. She ran screaming out of the room. I use the metro, but since I am afraid of germs, I always ride standing so I won't have to sit on those dirty seats! She ironed standing. In this sentence "standing" is an adverb of manner or attendant (accompanying) circumstances. It answers the question "How did she iron?" Mrs.Stone claimed that she had been paralyzed from the waist down in an auto accident and sued the the insurance company for 15 million dollars. An eyewitness for the insurance company claimed however that Mrs.Stone did not iron her clothes while sitting in her wheelchair but that she ironed standing. --------- She ironed while standing........In this sentence 'standing' is an object of the conjunction 'while' expressing an action going on at the same time.

#3 is good. But it really means: "He ate his meal (while) standing." The "while" has bee left out. "standing" is not an adverb. For the above reasons, #1 and #2 are wrong. 1. She did the ironing. (you usually stand when you do the ironing) 2. I had to stand all the way on the subway. (I went there standing...is nonsense)

'Standing' is either a noun ,an adjective or a verb in the continuous tense" to be + standING". You can't use it as an adverb to describe the subject doing an action in a standing position: 1. In the first sentence it is redundant to describe the act of 'ironing' as being done in a standing position,because it is usually done so,but if you like to mention it then you could say: "She ironed while standing (or on her feet) 2. You can't use 'standing' as an adverb to describe the state of standing in the subway. You could simply use the verb 'stand' instead: I had to stand,because... 3.The same goes for the third sentence, you can't use 'standing 'as an adverb. You could say instead: "He stood while eating his meal." There are some other ways to express the previous sentences.Some other italkians will be certainly giving you further examples:)