Digit cooling influences grasp efficiency during manipulative tasks

Abstract

A commonly experienced effect of cold is a sensation of numbness and loss of sensibility in the fingers. Intact tactile sensibility of the grasping digits is essential for the efficient scaling of grip force level during the manipulation of hand-held objects. We investigated whether or not cooling of the grasping digits affects scaling of the grip force magnitude in relation to the loads resulting from continuous vertical arm movements performed with a grasped instrumented object. Maxima and minima of load force occurred at the lower and upper turning point of the movement cycle, respectively, and were accompanied by maximum and minimum peaks in grip force occurring close in time prior to and following digit cooling, respectively. Thus, digit cooling did not influence the ability to adjust the grip force profile in anticipation of movement-induced fluctuations in load force. However, subjects established significantly higher grip forces against the hand-held object following digit cooling and generated a 10-70% higher ratio between grip and load forces at the upper and lower turning points of the movement cycle. It is thought that the impaired economical scaling of grip force level is the result of reduced sensory feedback from the grasping fingers during digit cooling. The results provide further evidence to support the suggestion that cutaneous afferent input plays a subordinate role in the predictive temporal regulation of the grip force profile, but is used to adapt economically the force level to the actual loading requirements during dynamic object manipulation.

Finger pad friction and its role in grip and touch

“…Moreover, data from studies involving healthy participants with experimentally induced sensory deficits and from patients with sensory loss, because of peripheral nerve damage or central brain lesions, clearly demonstrate the central role of somatosensory feedback for dexterous manipulation. Several methods have been used to transiently interrupt sensory information from the hands of healthy subjects: the use of gloves [6], cooling with sprays or gels [7] and injections of local anaesthetics [8,9]. An almost invariable effect of these manipulations was an increase in the grip force applied against the grasped object.…”

Functional sensibility assessment. Part I: develop a reliable apparatus to assess momentary pinch force control

“…5 The specification was a cuboid in consideration of hand ergonomics. 23 The apparatus had three components: (1) a specially designed steel cuboid (weight ¼ 480 g, 6.0 Â 4.5 Â 9 cm) that provided space for an accelerometer; (2) (Fig.…”

“…2 Previous researchers demonstrated that impaired control resulted in less precise adjustments in the friction force between the object and finger pulps owing to poor digital sensation by the local anesthesia on the digits or a long-term deprivation of digital sensation. [3][4][5] Any sensory deficit might contribute to permanent impairment, so that complete loss of palmar sensation of these parts is considered a 50% deficit of functional hand capacity. 6 However, few wellcontrolled works or apparati exist to investigate how sensory function contributes to the impairment of hand function.…”

Similar Motion of a Hand-held Object may Trigger Nonsimilar Grip Force Adjustments

“…G is modulated during shaking and point-to-point arm movements [2,3,5,27] as well as during locomotion [4]. Local skin anesthesia and digit cooling make the coordination of L and G less precise but does not change the general pattern of coordination [8,32,33]. When people lift an object from a support, they initially exert sufficiently large G force and only after that generate the force in vertical direction necessary to lift the object.…”