One possibility is that when the hand was in a more biomechanically constrained posture (i.e. palm up), variance in proprioceptive estimation increased and led to a bias towards the less biomechanically constrained postures.
Previous work suggests that neural coupling between proximal and distal muscles with changes in joint position is a possible mechanism but these studies tend to use artificially constrained postures that do not reflect activities of daily living.
The automated line, on the other hand, required higher skills, offered less constrained postures, lower loads and repetitiveness for the hands as well as frequent changes between different physical load levels.
Constrained postures, repetitive movements, heavy manual handling, lack of variation and insufficient recovery, are often cited as physical risk factors [ 3].
Because most studies examining the control of limb stiffness have constrained limb posture, it is unclear if posture selection is a critical component of endpoint stiffness regulation during more natural tasks in which the kinematic redundancies of the arm can be exploited to change posture without altering endpoint location.
Briefly, animals reached through a shoulder height portal that constrained their posture, with the whole arm extended, and then grasped a handle located outside of the chamber wall that was attached to a stationary force transducer (Futek Advanced Sensor Technology, Irvine, CA) (Additional file 1: Figure S1 and Additional file 2).
IK is exploited to reconstruct an anatomically correct posture of the user (i.e., its joint state) considering the 3D locations of selected end-effectors which are used to constrain the posture.
Each firm's ability to engage in innovative activities will be constrained by its posture, which is exogenous to the innovation process being measured.
To constrain participants' hand posture, two wooden frames locked the participant's wrists in the selected posture.
We used an operant model developed previously [ 22, 55- 58], in which rats reach forward using their whole forearm, into a portal that constrains their posture, for a handle located outside of the chamber, and then grasp the handle that is attached to a stationary force transducer, at a learned and defined reach rate and target force for a food reward.
