## 1 Introduction  
Maintaining balance is crucial for daily life and long-term health [1]. Whether we are still or moving, maintaining an upright trunk posture is essential for many activities, such as eating, dressing, and using electronic devices. Postural control is the ability to maintain the body in space and achieve both stability and orientation goals [2]. It is a complex sensorimotor skill [1], which involves the processing of sensory information [3] that also needs to be integrated with the central nervous system to proficiently plan, control, and execute correct movements [4]. To achieve good postural control, proper control of the trunk and core stability are essential. Although the terms \"trunk\" and \"core\" are often used interchangeably, they have different meanings [5]. The trunk refers to the human body apart from the head, neck, and limbs, while the core extends from the sternum down to the public bone, including every muscle surrounding the lumbar spine and pelvis, such as the abdominal, back, and hip muscles [5]. Core stability refers to the ability to control and stabilize the spine and pelvis during movements [5; 6], whereas trunk control refers to the ability to move and control the upper body in relation to the lower body. The former primarily involves the muscles around the lumbar spine and pelvis, whereas the latter involves the entire trunk, including the chest and shoulders. The close connection between trunk control and core stability stems from their dependence on synchronized muscle group activations [7]. Both play a vital role in facilitating functional body movements [5] and maintaining sitting balance [1]. Several factors affect our ability to appropriately control the trunk and core muscles, including neurological diseases, musculoskeletal injuries, and ageing [5]. These factors affect either the central nervous system or peripheral structures or impair the communication between them. Neurodegenerative disorders are responsible for a gradual, or sometimes rapid, worsening of postural abilities, while traumatic events cause sudden damage affecting these abilities. Traumatic events include spinal cord injuries (SCI) and stroke, both of which affect the central nervous system. The former occurs at the level of the spine, resulting in partial or total loss of sensation and motor functions below the level of the injury, while the latter affects a specific region of the brain, causing impairments in movement and sensation. In contrast, Parkinson's disease (PD) is primarily caused by the gradual degeneration of the basal ganglia [8]. Specifically, the degeneration of dopaminergic neurons in the substantia nigra pars compacta triggers a cascade of functional changes that affect the whole basal ganglia network, resulting in tremors, body rigidity, and instability [8]. In multiple sclerosis (MS), the gradual demyelination of nerve fibers in the central nervous system, in addition to pain, tingling, and numness in the limbs, causes a slowdown in the exchange of information between the brain and muscles, resulting in muscle weakness coupled with a range of motor and sensory impairments [9]. Despite different causes, these conditions share common deficits related to core stability and trunk control [10]. These deficits include difficulty in maintaining an upright posture, as well as problems with correctly perceiving the position of the body in space and reacting to self-generated changes or unexpected disturbances, muscle weakness, and difficulty in selectively activating muscles, often leading to body asymmetries, with a direct impact on the functional activities of daily living [11; 12; 13; 14]. Rehabilitation programs that focus on enhancing core stability, trunk control, and sitting balance have the potential to assist individuals in restoring their capacity to sit and engage in activities with enhanced comfort and self-assurance [15; 16]. These rehabilitation programs are diverse in terms of the exercises, equipment, and approaches employed to address these impairments.