Precision of a pointing movement performed with either the dominant or non-dominant hand is linked to the timing of anticipatory postural adjustments

Introduction: It is a common experience to feel motor awkwardness when performing a pointing movement with the non-preferred limb, which is known to be associated to less precise movements. Here we provide evidence that this last behaviour partly stems from changes in the temporal organization of the Anticipatory Postural Adjustments (APAs) in the non-preferred side. Materials and methods: We investigated the effect of lateralization on APAs in Biceps Brachii, Triceps Brachii and Anterior Deltoid, which stabilize the arm when performing a pen-pointing movement (prime mover Flexor Carpi Radialis). Moreover, we analysed the elbow and wrist kinematics as well as the precision of the pointing movement. Results: The mean kinematics of wrist movement and its latency, with respect to prime mover recruitment, were similar in the two sides, while APAs in Triceps Brachii, Biceps Brachii and Anterior Deltoid were less anticipated when movements were performed with the non-dominant (20–30 ms) versus dominant hand (60–70 ms). APAs in the non-dominant limb were associated with an altered fixation of the elbow, which showed a higher excursion, and with a more scattered pointing error (non-dominant: 16.3 ± 1.7 mm versus dominant: 10.1 ± 0.8 mm). Discussion: By securing the dynamics of the more proximal joints, an appropriate timing of the intra-limb APAs seems necessary for refining the voluntary movement precision. The linkage between APAs, elbow fixation and movement accuracy also agrees with the recent suggestion that APAs and prime mover recruitment are driven by a shared motor command, which strives to obtain an accurate pointing.