Force Anticipation and Its Potential Implications on Feedforward and Feedback Human Motor Control

Abstract

Objective To investigate the effects of human force anticipation, we conducted an experimental load-pushing task with diverse combinations of informed and actual loading weights. Background Human motor control tends to rely upon the anticipated workload to plan the force to exert, particularly in fast tasks such as pushing objects in less than 1 s. The motion and force responses in such tasks may depend on the anticipated resistive forces, based on a learning process. Method Pushing performances of 135 trials were obtained from 9 participants. We varied the workload by changing the masses from 0.2 to 5 kg. To influence anticipation, participants were shown a display of the workload that was either correct or incorrect. We collected the motion and force data, as well as electromyography (EMG) signals from the actively used muscle groups. Results Overanticipation produced overshoot performances in more than 80% of trials. Lighter actual workloads were also associated with overshoot. Pushing behaviors with heavier workloads could be classified into feedforward-dominant and feedback-dominant responses based on the timing of force, motion, and EMG responses. In addition, we found that the preceding trial condition affected the performance of the subsequent trial. Conclusion Our results show that the first peak of the pushing force increases consistently with anticipatory workload. Application This study improves our understanding of human motion control and can be applied to situations such as simulating interactions between drivers and assistive systems in intelligent vehicles.

Threshold variations of medial pterygoid single motor units during vertical or horizontal force tasks

“…There is no information available as to activation of motor units in advance of recorded onset of force in an isometric jaw-motor task, although anticipatory jawclosing muscle activity has been noted during rhythmic open-close movements, 31 and muscle activity in advance of force has been well described in the limb motor system. 32 Further, activation of neurons in the tongue region of the face primary motor cortex has been reported in advance of EMG evidence of onset of a tongue protrusion movement. 33 The onset of motor unit activity prior to the onset of an increase in force in a task likely reflects the need for a progressive increase in force to take up elasticity in the system prior to force being recorded at the level of the force transducer.…”

A tensor decomposition reveals ageing-induced differences in muscle and grip-load force couplings during object lifting

“…However, a characterization of the motor patterns underlying these changes at the kinetic and muscle activation levels is currently missing. A potential explanation for this gap in the literature is the lack of a computational approach that enables characterizing the dynamic interaction between arm and hand muscle activations with grip and load force during grasp-lift-replace tasks 26 , 36 . As a result, even when differences in force variables are observed as a result of ageing, the corresponding differences in muscle activity remain largely unknown 49 .…”

A Tensor Decomposition Uncovers the Effect of Ageing on Muscle and Grip-Load Force Couplings During Grasping

“…However, our understanding of why OA adapt their grasping strategies is limited. A potential explanation for this gap in the literature is the lack of computational approach that enables characterising the dynamic interaction between arm and hand muscle activations with grip and load force during grasping [29, 20]. As a result, even when differences in force variables are observed as a result of ageing, their neuromuscular origins remain largely unknown [40].…”