I am no dancer, but I don't believe the context can support Mr. Garlock's interpretation:
The word in question (karar), is defined by BDB as "to whirl, to dance". However, since the word is only used twice (here and in v. 16), we shouldn't place too much confidence in the lexical precision. Rather, it is the context that clarifies what was going on.
In the first place (as DJClayworth astutely pointed out), the adverbial modifier "with all his might" suggests at the very least that this is an extremely expressive activity, utilizing all of David's extremeties, not merely his feet.
Secondly, verse 16 sheds even more light, combining karar with pazaz ("agile leaping"), lending further evidence that this was a full-bodied expression of celebration. In fact, it was exactly this uninhibited display that David's wife Michal "despised in her heart". Moreover, as your Gesenius source pointed out, the same word in the parallel passage (1 Chron 15:29), is exchanged with the word "raqad" ("jumping"), a word which is often used in Scripture to describe the excited skipping of young calves and goats.
But most crucially, it is precisely the undignified nature of David's display that serves as the central theme of his conversation with Michal (v. 20-22). She ridicules him for his "shameless" behavior (attacking his exuberant joy, just as the enemy of our souls attacks it in us), but David silences her, boldly maintaining that the Lord's magnamimous grace sometimes requires extravagant -- even "undignified" -- outbursts of emotion.
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So, Mr. Garlock can keep tapping his feet if he feels so inclined, but I suspect in heaven he may well be "jumping and leaping and praising God." (Ac 3:8)
