Interaction between position sense and force control in bimanual tasks.
Giulia Ballardini, Valentina Ponassi, Elisa Galofaro and 5 others
PMID 31703703WHAT IT FOUND
In healthy right-handed people, lifting two hands to the same height becomes inaccurate if the hands hold different weights.
The hand holding the lighter weight consistently stops lower. Force matching accuracy depends on the left hand's position, not on whether the arms are symmetric.
Key findings
01Asymmetric loading caused the hand holding the lighter weight to reach a systematically lower height than the hand holding the heavier weight.
02Symmetric loading (both hands holding equal weights) did not produce a significant difference in height between the two hands.
03In bimanual force matching, the left hand's position determined the force error, regardless of the right hand's position or symmetry of the setup.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study included only healthy right-handed subjects, so results may not apply to left-handed individuals or those with motor impairments. Muscle activity (EMG) was not recorded, so the neural mechanisms behind the proprioceptive errors were not directly measured. Tactile feedback and grip force were not controlled for in the force-matching task. The weight range tested was narrow (250g and 500g), so the findings may not hold for heavier loads.
Declared interests
Funded by FP7 People: Marie-Curie Actions and the Ministry of Science and Technology, Israel. No other conflicts declared.
The easy way to misread this
Do not assume these proprioceptive biases apply to patients with neurological deficits. The study tested only healthy right-handed adults, and the authors explicitly state this is a starting point for future clinical assessment, not a validated clinical tool for patient populations.