RESEARCH ARTICLE Hand immobilization affects arm and shoulder postural control Francesco Bolzoni • Carlo Bruttini • Roberto Esposti • Paolo Cavallari Received: 26 January 2012 / Accepted: 27 April 2012 / Published online: 23 May 2012 Ó Springer-Verlag 2012 Abstract It is a common experience, immediately after the removal of a cast or a splint, to feel motor awkward- ness, which is usually attributed to muscular and joint immobilization. However, the same feeling may also be perceived after a brief period of immobilization. We pro- vide 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 immo- bilization 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 adjust- ments and the focal movement. Keywords Motor control Á Posture Á APAs Á Immobilization Á Human Introduction It is well known that joint immobilization leads to signif- icant modification to the muscular and nervous system. Over the past few decades, several authors have docu- mented modifications in skeletal muscle properties such as atrophy (White et al. 1994; Hather et al. 1992), increasing in the intramuscular connective tissue (Jo ´zsa et al. 1990) and reduction in the maximal voluntary contraction strength (Veldhuizen et al. 1993; Hortoba `gyi et al. 2000) after cast immobilization. In contrast, only a few papers have examined the neural adaptations to immobilization. Liepert et al. (1995) showed that immobilization leads to a reduction of the cortical area of the inactivated muscle, while Facchini et al. (2002) demonstrated a decrease in the cortical excitability, without affecting nerve or muscle excitability, after only 4 days of motor restriction. Huber et al. (2006) found that these changes may even occur after 12 h of immobilization. Moisello et al. (2008) demonstrated that short-term immobilization affects inter-joint coordination by acting on feed-forward mechanisms, while Avanzino et al. (2011) showed that a brief period (10 h) of right-hand immobili- zation decreased the excitability of left primary motor cortex and reduced interhemispheric inhibition from left- to-right hemisphere. Finally, Langer et al. (2012) illustrated that the left cortical thickness of the sensorimotor cortex changed during right arm immobilization. We hypothesize that postural control, and especially anticipatory postural adjustments (APAs), may play a key role in the process leading to the motor impairment induced by immobilization. In fact, APAs are considered intimately coupled to several kinematics aspects of the primary movement, such as speed and trajectory (Kaminski et al. 1995; Pozzo et al. 2002; Bortolami et al. 2008; Kim et al. F. Bolzoni Á C. Bruttini Á R. Esposti Á P. Cavallari (&) Dipartimento di Fisiologia Umana, Universita ` degli Studi di Milano, Via Mangiagalli 32, 20133 Milan, Italy e-mail: paolo.cavallari@unimi.it 123 Exp Brain Res (2012) 220:63–70 DOI 10.1007/s00221-012-3115-7