勁, Jin or Jing?

[Altair]

In Taijiquan (太極拳), the character 勁 is a much used term of art; for example, it is used in the common expressions 發勁 ("issue power"), 聽勁 ("listening energy"?), 化勁 ("dissolving energy"?), and in the phrase 虚靈頂勁/虚領頂劲. Can someone tell me which reading to give 勁 in these phrases? My dictionaries seem to say that "jìn" is used for the noun usages, where 勁 means "strength" or "power"; whereas "jìng" is used for adjectival usages, where 勁 means "strong" or "powerful." From what I see reading articles in magazines, native Chinese speakers seem to favor the pronunciation "jìng." Could anyone tell me which reading to use for this character?

My dictionaries also say that 勁 also has differing pronunciations in Cantonese ("ging" in a mid level tone, and "gihng" in a low level tone) with apparently the same distinctions as in Mandarin. I would also appreciate it if someone could let me know which of these pronunciations is appropriate for the phrases above.