This paper presents a cooperative body part labeling and tracking
algorithm
  for locating body parts in a video image sequence. The body part labeling
procedure is used to initialize the tracking procedure and to prevent
tracking
from getting lost; and the tracking procedure is used to analyze frames
that cannot be handled reliably by the labeling procedure. This
results in an automatic and robust body part tracking system. Unlike
previous work that always start tracking from the first frame which may be
difficult to analyze, our tracking procedure starts with some key frames
in
which body parts can be located reliably. Key frames are selected based on
a
labeling confidence measure which evaluates the similarity between the
human   
model and the image features. The labeled body parts are tracked
in-between
frames based on such cues as shape, color, and location interpolated
between
key frames iteratively. The proposed algorithm has been applied to analyze
NASA videotapes in which crew members present challenging postures of
bending,
twisting, and rotating in a space station. The experimental results
demonstrate the effectiveness of the proposed algorithm.
(UMIACS-TR-2004-30)