Controlling posture, i.e., governing the ensemble of involuntary muscular activities that manage body equilibrium, represents a demanding function in which the cerebellum plays a key role. Postural activities are particularly important during gait initiation when passing from quiet standing to locomotion. Indeed, several studies used such motor task for evaluating pathological conditions, including cerebellar disorders. The linkage between cerebellum maturation and the development of postural control has received less attention. Therefore, we evaluated postural control during quiet standing and gait initiation in children affected by a slow progressive generalized cerebellar atrophy (SlowP) or non-progressive vermian hypoplasia (Joubert syndrome, NonP), compared to that of healthy children (H). Despite the similar clinical evaluation of motor impairments in NonP and SlowP, only SlowP showed a less stable quiet standing and a shorter and slower first step than H. Moreover, a descriptive analysis of lower limb and back muscle activities suggested a more severe timing disruption in SlowP. Such differences might stem from the extent of cerebellar damage. However, literature reports that during childhood, neural plasticity of intact brain areas could compensate for cerebellar agenesis. We thus proposed that the difference might stem from disease progression, which contrasts the consolidation of compensatory strategies.

Background: Power and energy at the ankle joint during gait are usually computed considering the foot as a rigid body. The foot is instead a deformable structure and can absorb and produce energy by pronation/supination, foot arch deformation and other intrinsic movements.Research question: Is it feasible to improve the foot power and energy estimation during gait with a simple gait analysis protocol?Materials and Methods: The power exchanged between the foot and the shank was computed as the sum of rotational and translational power, intrinsically considering the foot deformation ("Deformable Foot method", DF). By this method the only shank movements and ground reaction forces need to be analysed. Eighteen healthy subjects were evaluated while walking barefoot and shod at different velocities. We then compared the obtained results with those obtained by the conventional power and energy calculation method ("Ankle Joint method", AJ). Results:The DF method showed a consistent negative peak of power absorption during the load acceptance (-1.16±0.47 W/Kg barefoot, -1.08±0.44 W/Kg shod), barely visible with the AJ method (-0.23 ±0.09 W/Kg barefoot, -0.30±0.09 W/Kg shod). The maximum power production calculated with the DF method (2.44±0.56 W/Kg barefoot, 2.49±0.57 W/Kg shod) was significantly lower than to the one calculated with the AJ method (3.15±0.68 W/Kg barefoot, 3.09 ±0.69 W/Kg shod). Similarly, the final energy values, the energy absorbed and produced were different between the two methods.Significance: Neglecting the foot deformations during gait leads to underestimate power absorption and overestimate power production. The DF method does not require a complex gait analysis protocol and can provide important information about the internal structure of the foot, thus improving physiological and clinical assessment.

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This review aims to highlight the important contribution of the cerebellum in the Anticipatory Postural Adjustments (APAs). These are unconscious muscular activities, accompanying every voluntary movement, which are crucial for optimizing motor performance by contrasting any destabilization of the whole body and of each single segment. Moreover, APAs are deeply involved in initiating the displacement of the center of mass in whole-body reaching movements or when starting gait. Here we present literature that illustrates how the peculiar abilities of the cerebellum i) to predict, and contrast in advance, the upcoming mechanical events; ii) to adapt motor outputs to the mechanical context, and iii) to control the temporal relationship between task-relevant events, are all exploited in the APA control. Moreover, recent papers are discussed which underline the key role of cerebellum ontogenesis in the correct maturation of APAs. Finally, on the basis of a survey of animal and human studies about cortical and subcortical compensatory processes that follow brain lesions, we propose a candidate neural network that could compensate for cerebellar deficits and suggest how to verify such a hypothesis.