Externally guided control of static grip forces by visual feedback - age and task effects in 3-6-year old children and in adults

This study has been devised to examine the visual feedback control of stati c grip force levels by pinch and by hand grip during pre-school age and in adults. 69 3-6-year old children and 17 adults were asked to establish and hold grip force levels defined by a visual target and feedback on the domin ant and non-dominant hand by hand grip and by pinch grip. From 3 to 6 years of age, the time needed to establish requested grip force levels decreased by a third and the precision increased two-fold for hand grip but four-fol d for pinch grip; in contrast to younger children, 5-6-year olds showed a m arked superiority of 60% for the pinch grip compared to hand grip, decreasi ng to about 40% in adults. In the case of pinch grip, all individuals had w orse results on higher force levels (children: 50%, adults: 32%). The young children generally tended to use too much force. Older children and adults were better by 75% under the condition of visual feedback vs. internal pro prioceptive control (after withdrawing visual feedback). In contrast to pre vious findings in anticipatory grip force regulation, externally guided for ce regulation begins to develop during late nursery age. Specific developme ntal effects were found for grip style and for the ability to use visual fe edback and to change from external to internal (proprioceptive) control, an d to a lesser extent for force magnitude but not for hand laterality and ge nder. The findings are interpreted by different developmental velocities of motor areas which are responsible for force regulation mechanisms and for grip style. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.