Analysis of finger motion coordination during packaging interactions

Packaging accessibility is a significant problem for many older people. Whilst the majority of studies have focused on issues surrounding strength, work has shown that dexterity required to open a pack is also a major issue for many older people. Hence, the work undertaken here, reports a quantitative study that aimed to analyse motion coordination patterns across digits 2–5 (index to little finger) during interactions with three of the most common types of packaging: plastic bottles, jars, and crisps packets, and comparing those interactions to a common measure of dexterity, the Perdue Pegboard. Ten subjects (6 males and 4 females) were examined while reaching forward to grasp and open a 300ml plastic bottle and a 500g jar. A ten-camera opto-electronic motion capture system measured trajectories of 25 miniature reflective markers placed on the dorsal surface landmarks of the hand. Joint angular profiles for 12 involved flexion–extension movements were derived from the measured coordinates of surface markers. The results showed that finger correlations vary widely across the differing pack formats with the crisps having the lowest finger movement correlation and the jar having the highest. Speed and jerk metrics were also seen to vary across the various pack formats. However, finger correlations were seen to be more relevant to perceived dexterity of pack opening than finger speeds and jerk motions.