Abstract
We studied the effect of abolishing cutaneous sensation (by infiltrating local anaesthetic around the median nerve at the wrist) on the ability of 10 healthy volunteers (a) to maintain a submaximal isometric pinch‐grip force for 30 s without visual feedback, and (b) to perform a fine finger‐manipulation „handwriting”︁ task. Blocking cutaneous sensation had no effect on ability to maintain pinch force, suggesting that muscle afferents have the major role in force‐control feedback. However, a near‐linear fall in force, present with or without block (mean slope = −1.3 ± 0.2% s^−1^), which cannot be attributed to motor fatigue, reveals a shortcoming of the afferent feedback system. Blocking cutaneous sensation did impair ability to perform the more demanding writing task, as judged by an 18 ± 6% increase in the length of the path between target points, a 22 ± 9% increase in the duration of the movement and a 63 ± 24% in „normalised averaged rectified jerk”︁, an averaged time‐derivative of acceleration (all significantly nonzero, P < 0.04). These experiments demonstrate the relative importance of muscular and cutaneous afferent feedback on two aspects of hand performance, and provide a way to quantify the deficit resulting from the lack of cutaneous sensation. © 2003 Published by Elsevier Ltd. on behalf of Orthopaedic Research Society. All rights reserved.