AAI_2025_Capstone_Chronicles_Combined

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Figure 2.4 Wrist speed (top) and elbow angle (bottom) over a 25-second meal segment.

the strong temporal structure around it, motivating models that focus on brief, well-localized positive segments within very long background sequences. Figure 2.3 illustrates wrist trajectories over a short time interval for a representative meal, plotted separately for intake and non-intake segments. During intake, the wrist trajectory forms a compact path directed toward the face, reflecting a purposeful hand-to-mouth motion.

In contrast, during non-intake periods such as resting or chewing without new intake, the wrist trajectory remains more diffuse and does not consistently converge toward the face. The figure highlights this contrast by showing distinct trajectory shapes across the two activity types rather than relying on subtle differences in instantaneous speed or joint angle. When we look at the full sequence in time, we see that intake moments are not isolated spikes but short, structured episodes. Figure 2.4 plots right and left wrist speed (top) and elbow angle (bottom) over the first twenty-five seconds of the clip, with shaded bands indicating the ground truth actions (for example, pick up tools with both hands, move hand towards mouth, eat it, and move hand away from mouth). Brief bursts of high wrist velocity appear precisely inside the green and red bands where the utensil moves toward the mouth and food is consumed, and they are accompanied by rapid elbow flexion followed by a more gradual extension as the arm returns to the table. In contrast, the long orange “food in hand at table”

Figure 2.3. Wrist XY paths for left and right hands during the first 5 seconds of a sample meal.

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