# Exergaming-Based Rehabilitation for Lateral Trunk Flexion in Parkinson's Disease: A Pilot Study
## 1 Introduction  
Axial postural deformities are a characteristic motor feature of Parkinson's disease (PD) [1]. Although it is difficult to identify a clear prevalence due to the lack of a comprehensive classification in previous years, lateral trunk flexion (LTF) and Pisa syndrome (PS) are the most common postural deformities in PD, with an estimated prevalence of approximately 8.8% [1, 2, 3, 4, 5, 6, 7]. Pisa syndrome is clinically defined as a reversible lateral flexion of the trunk of at least 10\({}^{\circ}\), which can be reduced through passive mobilization or supine positioning, while it worsens in sitting, standing, or walking [7, 8]. In contrast, lateral trunk flexion is clinically defined as an involuntary lateral bending of the trunk with an angle ranging from 5\({}^{\circ}\) to 10\({}^{\circ}\), and can be considered as a milder form of Pisa syndrome [1, 2, 3, 4, 6, 7].  
LTF significantly reduces quality of life. In fact, increased lateral bending is related with limitations in activities of daily living (ADLs), motor impairment, increased back painintensity, imbalance, and increased risk of falling [5]. The cut off that identifies severe motor impairment and high disability is a lateral bending angle exceeding 10.5\({}^{\circ}\)[5]. Consequently, the treatment of these correlated symptoms is pivotal in order to prevent progression and worsening of LTF.  
These correlated symptoms are usually managed with pharmacological approaches such as onabotulinumtoxin-A [9; 10], non-pharmacological interventions such as rehabilitation [11], or a combination of both [12]. However, rehabilitation programs are heterogeneous, and there is ongoing debate about the best intervention type and for how long it should last [13].  
Exergaming, which combines physical exercise with interactive video games, has emerged as a promising tool in rehabilitation. From a psychological point of view, its engaging nature has the potential to both enhance motivation and improve therapy adherence. By incorporating gamification elements such as rewards, challenges, and real-time feedback, exergaming transforms traditionally monotonous rehabilitation exercises into appealing activities. Exergaming significantly increases intrinsic motivation in patients by fostering a sense of autonomy, competence, and relatedness [14]. Exergames have also improved balance and mobility in older adults [15], provided higher adherence rates and greater enjoyment compared to standard care in cancer patients [16], and improved exercise capacity and quality of sleep in heart failure patients [17]. This growing body of literature indicates that exergaming can boost motivation through enjoyable, interactive modalities while simultaneously promoting adherence to therapy regimens.  
With regard to exergaming in PD, today, rehabilitation protocols based on virtual reality and exergaming have emerged as a valid training strategy to improve balance, mobility, and gait in [PERSON]'s disease. These approaches provide individuals with PD the opportunity to experience more sensory stimulation and motor tasks while receiving real-time feedback [18; 19; 20; 21; 22; 23; 24]. However, up to now, there has been no detailed investigation addressing the use of a virtual reality or exergaming approach for managing lateral trunk flexion in [PERSON]'s disease.  
The first aim of this study is to investigate the clinical effects of a rehabilitation treatment based on exergaming on clinical outcomes such as motor impairment, imbalance, and risk of falling. The second aim is to assess the neurophysiological effect of an exergaming-based rehabilitation treatment on the contractile properties and on the pressure pain thresholds of specific trunk muscles.