Grip force dynamics in the approach to a collision

Abstract

This experiment investigated the prediction of load force (LF) in impulsive collisions inferred from anticipatory adjustments of grip force (GF) used to stabilise a hand-held object. Subjects used a precision grip to hold the object between thumb and index finger of their right hand and used the arm either: (1) to move the object to produce a collision by hitting the lower end of a pendulum, causing it to swing to one of three target angles, or (2) to hold the object still while receiving a collision produced by the experimenter releasing the pendulum from one of three angles. Visual feedback of the pendulum's trajectory was available in the production task only. In all conditions, subjects increased GF in advance of the collision. In receiving the collision without advance information, subjects set GF levels to the mid-range of the experienced forces. When subjects possessed knowledge about the maximum angle of pendulum swing - either because they were going to produce it or because they were verbally informed - magnitude of the anticipatory-GF magnitude response was scaled to the predicted LF magnitude. Furthermore, GF was scaled to LF with a higher gain when producing compared to receiving the collision. This suggests that updating forward models through a semantic route is not as powerful as when the updating is achieved through the more direct route of dynamic exploration.

Biomechanics and visual-motor control: how it has, is, and will be used to reveal the secrets of hitting a cricket ball

“…Turrell et al (1999) and Li and Turrell, (2002) proposed that when receiving a collision -as would occur when playing a defensive stroke -the changes in grip forces are minimal prior to bat -ball contact, whereas large changes occur post-impact due to a latency reflex to prevent the bat from slipping from the hand. When producing a collision -as occurs when performing an attacking stroke -peak grip forces were observed at impact to ensure forces are transferred to the ball.…”

Influences of Load Characteristics on Impaired Control of Grip Forces in Patients With Cerebellar Damage

“…In healthy subjects, equivalent results were found by Hermsdörfer and Blankenfeld (2008) who argue that continuous sinusoidal load changes are predictable due to their repetitive time course and therefore do not solely rely on reactive mechanisms. These authors hypothesize that during external load changes reactive and predictive mechanisms are combined in a flexible way depending on task conditions (see Hermsdörfer and Blankenfeld 2008;Turrell et al 1999). In addition, the updating of the ongoing grip-force response may require a shorter time than its initiation in sudden load steps (Johansson et al 1992a).…”

“…The finding of impaired precision during sinusoidal and sinusoidal-like loads leaves open the possibility that reaction during rapid load changes that occur at arbitrary time points-as for example tested in catching and illusion experiments (Nowak et al 2004;Turrell et al 1999)-may be better preserved following cerebellar damage. Therefore in a second control experiment sudden externally generated load jumps were produced.…”

Effects of Gait Variations on Grip Force Coordination During Object Transport

“…Typically, when unpredictable loads are applied to a handheld object, feedback is used to track inertial changes and make appropriate grip force adjustments (e.g., Cole and Abbs 1988;Delevoye-Turell et al 2003;Johansson and Westling 1988;Johansson et al 1992a,b;Macefield and Johansson 1996;Nowak 2004;Serrien et al 1999;Turrell et al 1999). Consistent with this finding, we observed that when stepping on an unpredictable, pliant obstacle, peak grip force lagged peak inertial force by ϳ95 ms, indicating that feedback may be used to generate an appropriate response (Cole and Abbs 1988;Westling 1984, 1987).…”