Small forces that differ with prior motor experience can communicate movement goals during human-human physical interaction.
Andrew Sawers, Tapomayukh Bhattacharjee, J Lucas McKay and 3 others
PMID 28143521WHAT IT FOUND
Small hand forces during blindfolded partner stepping varied with movement phase and dancer expertise, indicating they can communicate movement goals.
Expert pairs used larger forces and improved synchronization, but patients were not studied.
Key findings
01Expert-expert dyads used significantly larger peak interaction forces than novice-novice dyads in both predictable and unpredictable stepping tasks.
02Interaction force magnitude differed across initiation, forward, backward, and change-of-direction phases in all dyad types.
03Only expert-expert dyads significantly improved spatial synchronization with practice, and force range did not change significantly in any group.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study used healthy expert and novice dancers, not patients or therapist-patient dyads, so it does not show what happens in rehabilitation. The reported participant and dyad counts are internally inconsistent, which makes the sample size hard to verify. The task was artificial: partners wore blindfolds, could not hear each other, and only hand forces were studied. Only force magnitude was analyzed, not the timing pattern of forces, and only one hand pair was used. Practice effects were measured only within the session, not after a retention period or on individual mobility.
Declared interests
The work was funded by the Division of Emerging Frontiers in Research and Innovation (US), the Foundation for the National Institutes of Health, and the National Institute of Child Health and Human Development. No author conflict-of-interest declaration is given in the supplied text.
The easy way to misread this
Do not conclude that therapist-patient hand forces improve patient rehabilitation. The study tested healthy expert and novice dancers in a lab stepping task, not patients or therapy outcomes.