What They Did
The researchers recruited 26 participants for a study of the
effect of cognitive tasks on postural sway while walking. (Postural sway refers
to the subtle movements used to maintain balance while standing or moving. Everyone
has some sway, but a large amount can indicate problems with balance.) Participants
first walked 10 meters in a straight line at a comfortable pace to get a
baseline for their speed and sway using smartphone accelerometers; this was
repeated three times for each participant.
In the next phase, participants were randomly assigned
cognitive tasks while walking. The tasks included: listing the months in
reverse order, naming category members that begin with a given letter,
participating in typical question-answer conversation, counting backwards from
100 by 3’s, spelling five-letter words backwards, and indicating whether a
number is larger or smaller than 50. Participants also rated the difficulty of
each task on a scale of 0 to 10. On average, the conversation task was
perceived by participants as the easiest, and the tasks of counting or spelling
backwards were the most difficult. The other three tasks were in-between and
were all about the same difficulty.
The researchers did not find a strong overall correlation
between task or perceived difficulty and sway. Although the relationships
between perceived difficulty and measurement of sway were significantly
correlated for some tasks, the direction of correlation varied. Furthermore,
each task showed a significant correlation between difficulty and sway for only
one of four sway measurements, and the correlated measurement varied across
tasks.
Further Exploration
Although the correlations between difficulty and sway were
minimal, the researchers noted that the difficulty ranking could have clinical
applications. When patients have rehabilitation for walking, clinicians
increase the challenge by asking them to perform cognitive tasks. The study
suggests that basic conversations should be the first challenge, followed by
listing the months backwards, listing items that start with a given letter, or
determining whether a number is greater or less than 50. Later, the clinician
can challenge the patient to count or spell backwards. The researchers also
note that, because the participants had no difficulty walking, the effects of
cognitive demands on sway may have been too small to detect. A sample of people
with at least minor mobility difficulties might be a better source of
information.
The difficulty ratings for the cognitive tasks generally
match my own. I’d definitely find the conversation the easiest, probably
followed by the listing task, then the classification of a number as over or
under fifty, followed by reciting the months backwards, then counting backwards
by 3’s, then finally spelling words backwards.
It feels like the difficulty correlates with how much I have
to visualize to complete the task. Conversation and list making don’t require
any visualization, but spelling a word backwards means holding an image of the
word in mind and “reading off” the letters in reverse order. I’m curious about
how my sense of the reasons for task difficulty aligns with empirical evidence,
but that’s a rabbit hole for another day!
https://commons.wikimedia.org/wiki/File:Walking_gait_cycle.png
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