I have gone with the semi-common wisdom that bluffers will lock their feet in position (frequently around the legs of the chair) and people value betting will have much more relaxed legs/feet and movement.
However, ... I also know that anxiety can result in a lot of leg/foot movement. A google search of "foot movement and lies" will tell you that both movement and non-movement are signals of a lie.
I got extra curious after watching a hand last night. A guy with 3 friends watching him bet a paired flop, turn and river while his legs were moving quite noticeably. He was also cautiously called down by someone I thought was a better player (who had flopped trips, with a weak kicker).
At showdown, the bettor was bluffing.
This is making me question my simplistic interpretation of leg/foot movement.
Bluffing can be associated with a wide range of mental states depending on the type of bluff, the type of opponent, the skill of the bluffor, his confidence in the bluff. This is further modulated by his emotional control as well as his ability to contain his physical tells.
No one is bluffing with Aces pre, but plenty can become anxious about handling post flop play with them, or just get excited.
In certain situations where you could be checking for a bluff, it could be a useful enough tell. You might give away some info by continually looking under the table though.
Good strategy if there are ladies at the table as they are much more prone to this type of tell, i used this a lot in a card room i used to play in.
