Radak citing his father: This is phlegm, like Kicho v'Ni'o (Bava Kama 3b).

Radak: Some say that this is like Chiki (we reverse the letters). I cannot speak (for my palate is dry).

Radak citing Ibn Ezra: My strength. Normally, human life depends on moisture to connect and stand up the body. The moisture is called Ko'ach; it is dry, like happens to old people.

Malbim: Not only are all my external and internal limbs perturbed. Also my strength departed. It is as if my strength and bodily moisture dried like earthenware, and I cannot regain my strength.

Rashi: They are the gums. One who is pained, saliva is not abundant in his mouth. Radak - the gums are above and below the tongue. This is like "u'Leshonam l'Chikam Davkah" (Iyov 29:10). The prefix Lamed is omitted; it is as if l'Malkochai. They are called Malkochim because Lokchim (they take) the food at the time of chewing.

Rashi citing Menachem: This is [tongs,] like "b'Melkachayim Lakach" (Yeshayah 6:6). They are the teeth, which are like smiths' tongs.

Radak citing Shocher Tov #1: It is my esophagus.

Radak citing Shocher Tov #2: The decrees against Torah in Galus were Mevatel me from two Toros, written and oral - "Ki Lekach Tov Nasati Lachem" (Mishlei 4:2).

Rashi: It is the depression of death.

Radak: It is the grave. I am close to death, as if You prepare me. I am ready to be put in the grave. Malbim - I have no hope to be saved, for my strength cannot return (refer to 22:16:1:4), and I cannot even scream, for my tongue clings to my palate!

Rashi: You seat me. It is an expression of Shefisah of a pot (putting it on an oven), "Shefos ha'Sir" (Melachim II, 4:38). Menachem explains every 'Shefisah' to be putting.

Radak citing Shocher Tov: I am like an oven put between two roads, and travelers put pots on me.