title: Hand immobilization affects arm and shoulder postural control.
abstract: It is a common experience, immediately after the removal of a cast or a splint, to feel motor awkwardness, which is usually attributed to muscular and joint immobilization. However, the same feeling may also be perceived after a brief period of immobilization. We provide evidence that this last effect stems from changes in the cortical organization of the focal movement as well as in the associated anticipatory postural adjustments. Indeed, these two aspects of the motor act are strongly correlated, although scaled in different manners. In fact, they are both shaped in the primary motor cortex, they both undergo similar amplitude and latency modulation and, as we will show, they are both impaired by the immobilization of the lone prime mover. Neuromuscular effects of limb immobilization are well known; however, most papers focus on changes occurring in the pathways projecting to the prime mover, which acts on the immobilized joint. Conversely, this study investigates the effect of immobilization on anticipatory postural adjustments. Indeed, we show that 12 h of wrist and fingers immobilization effectively modify anticipatory postural adjustments of the elbow and the shoulder, that is, those joints not immobilized within the fixation chain. Accordingly, the motor impairment observed after short-term immobilization most likely stems from the unbalance between anticipatory postural adjustments and the focal movement.
authors.affiliation: Dipartimento di Fisiologia Umana, Università degli Studi di Milano, Via Mangiagalli 32, 20133 Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bolzoni
authors.forename: Carlo
authors.initials: C
authors.lastname: Bruttini
authors.forename: Roberto
authors.initials: R
authors.lastname: Esposti
authors.forename: Paolo
authors.initials: P
authors.lastname: Cavallari
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001132:Arm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation*; D006801:Humans; D007103:Immobilization / Q000379:methods*; D008297:Male; D009068:Movement / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult