Postural forearm changes induced by predictable in time or voluntary triggered unloading in man

Abstract

Human subjects sitting in a chair were asked to maintain their right forearm in a horizontal position in half supination. The forearm was loaded with a constant weight of one kilogram. Vertical force at the wrist level, angular position of the elbow and EMG activity of biceps, brachio-radialis and triceps muscles were recorded. Unloading was tested under four different conditions, the first two having been used in a previous study (Hugon et al. 1982): Voluntary unloading by the subject's other hand. An "anticipatory" deactivation of the load bearing forearm flexors is observed preventing the elbow rotation of that arm. Unpredictable passive unloading. This results in an upward forearm rotation which provokes the classical "unloading reflex". Two new conditions were tested in the present paradigm: Imposed unloading predictable in time (tone signal preceding unloading by a fixed interval). Unloading being actively triggered when the subject presses a key. Under the two latter conditions, no anticipatory deactivation of the flexor supporting muscles preceding the onset of unloading as in situation A was observed. During the first 120 ms after the onset of unloading, the forearm rotation was the same as in situation B (unpredictable passive unloading). Thereafter, the rotation was smaller in some subjects, apparently due to an ameliorated reflex action. It is concluded that temporal information concerning the precise time of the unloading or the triggering of the load release by a voluntary movement (key press) was not by itself able to induce the anticipatory deactivation of the forearm flexors that was seen with a coordinated voluntary release of the load by the contralateral arm.

Early compensatory and anticipatory postural adjustments following anterior cruciate ligament reconstruction

“…This is in agreement with previous studies on bimanual tasks, wherein an anticipatory adjustment of the forearm muscles in one upper limb prevents the postural disturbances related to a forthcoming selfinitiated movement of the contralateral upper limb (Dufossè et al 1985;Bennis et al 1996;Massion et al 1999). In the perturbation task adopted in the present study, APAs of the involved limb muscles must be implemented by the central nervous system (CNS) to predict and prevent the perturbing consequences of the supporting limb action, hence bypassing long delays associated with 16 feedback (Santello 2005;Aimola et al 2011).…”

“…Any motor act combines the displacement of one or more segments toward a given goal and the postural stabilization of other segments (Dufossè et al 1985;Massion 1992;Bennis et al 1996;Baldissera et al 2008;Bolzoni et al 2012). Postural stability is achieved during voluntary movement by compensatory and anticipatory strategies aimed at minimizing unpredictable and predictable disturbances, respectively (Bennis et al 1996;Kanekar and Aruin 2014).…”

“…Postural stability is achieved during voluntary movement by compensatory and anticipatory strategies aimed at minimizing unpredictable and predictable disturbances, respectively (Bennis et al 1996;Kanekar and Aruin 2014). Since the work by Hugon et al (1982), a number of authors have investigated compensatory and anticipatory strategies using bimanual loading/unloading tasks of the upper limb (Dufossè et al 1985;Bennis et al 1996;Massion et al 1999). When a loading/unloading perturbation to the forearm is imposed 4 unexpectedly by the experimenter, compensatory postural adjustments (CPAs) are observed at the level of the forearm muscles following the perturbation.…”

Hierarchies of synergies: an example of two-hand, multi-finger tasks

“…Examples include the coordination of articulators during speech (Abbs and Gracco 1984), of arms during loading and unloading (Dufosse et al 1985;Paulingnan et al 1989), of joints during pointing, reaching, standing-up, and swaying (Domkin et al 2002;Freitas et al 2006;Scholz and Schöner 1999;Wang and Stelmach 1998), of muscles during standing and stepping (Krishnamoorthy et al 2003;Wang et al 2005), and of digits during pressing, grasping, and holding an object (Gao et al 2005;Santello and Soechting 2000;Scholz and Latash 1998;Shim et al 2005). Very few studies, however, have addressed synergies at different levels of an involved control hierarchy.…”

Time on your hands: Perceived duration of sensory events is biased toward concurrent actions.

“…It is essential that we represent not only the nature of our action outcomes (e.g., sight of lifting; 'what' information), but also crucially, the onset and duration of these outcomes (e.g., the duration of the lifting interval; 'when' information). For example, lifting the teacup from a saucer requires an anticipatory response to maintain postural stability (Diedrichsen, Verstynen, Hon, Lehman, & Ivry, 2003;Dufossé, Hugon, & Massion, 1985). Similarly, anticipating the duration of the lift phase is essential for coordinating hand and mouth gestures, and when shaking someone's hand, contact must be made for an appropriate length of time -neither too long, nor too short -to convey the intended social message.…”