## 1 Introduction  
Ankle balance deficits represent a significant issue in the health field as they are closely associated with an increased risk of ankle sprains [1]. Proprioception plays a crucial role in maintaining balance and joint stability, and its impairment can reduce the body's capacity to sense joint position and movement, leading to instability and a heightened risk of re-injury [2]. These deficits often result in chronic ankle instability (CAI), which negatively impacts individuals' quality of life and functional capacity [3]. A contributing factor during an ankle sprain is the delayed activation of the peroneal muscles in the presence of fatigue [4]. Additionally, following an ankle sprain, morphological changes and alterations in the pennation angle of the peroneus longus often occur [5], perpetuating a vicious cycle that promotes recurrence. This highlights the need for interventions aimed not only at addressing the acute injury but also at preventing future recurrences through strengthening and functional re-education. Given the high incidence of ankle sprains linked to balance deficits, it is essential to explore effective training methods to enhance balance and prevent injuries. Various training methods have been proposed to enhance balance and decrease the risk of ankle injuries [6]. Among these, instability devices have demonstrated particular effectiveness in strengthening and stabilizing the ankle, as these devices challenge the neuromuscular system, thereby improving proprioception and balance [7]. In this regard, recent evidence suggests a transition toward smaller and more portable devices, known as selective instability devices [8], which can offer similar benefits for ankle balance training when compared to larger, heavier, and less portable global instability devices (e.g., the widely used Both Sides Utilized (BOSU)) [9]. An example of such a device is the Blackboard (BB), a configurable wooden device composed of two interconnected boards with independent movement. Its bottom surface features Velcro, allowing the user to freely place half-cylinder slats, thereby directing the instability to specific areas of the foot (e.g., the forefoot, rearfoot, or targeted pronation/supination movements). To optimize the process of balance training, recent research has explored the combination of exercise-based programs with additional therapeutic modalities to enhance training outcomes [10; 11; 12]. One emerging modality in this context is transcranial direct current stimulation (tDCS), a non-invasive low-intensity galvanic current neuromodulation technique that has shown promising results in enhancing motor learning by modulating primary motor cortex excitability (M1) [13]. This is particularly relevant since individuals with CAI exhibit reduced cortical excitability in M1, altered somatosensory cortex activation in response to joint loading, and increased reliance on visual and planning areas during simple movement execution compared to uninjured controls [14; 15]. Clinical interventions targeting these neural alterations, such as tDCS interventions, could play an important role in ankle balance training programs. In healthy participants, anodal tDCS over the M1 leg area has shown effectiveness in promoting balance performance in a dynamic balance task relative to sham tDCS [16], as confirmed as well in the systematic review and meta-analysis by [PERSON] (2019) [17]. tDCS delivers low-amplitude electrical currents to modulate cortical excitability, facilitating neural plasticity and enhancing the capacity for skill acquisition [18; 19]. While its application in motor learning and rehabilitation is relatively novel, preliminary research suggests that tDCS can optimize training outcomes when combined with the performance of specific tasks [20; 21]. In fact, the application of tDCS over M1 has proven effective in enhancing motor learning both within and across sessions, in addition to improving the consolidation of this learning.