# Arm Swing Movements during Walking as an Early Predictor of Multiple Sclerosis Progression
## 1 Introduction  
Multiple sclerosis (MS) is the most common inflammatory and demyelinating disease of the central nervous system [1] characterized by motor and sensory deficits, cerebellar symptoms, and balance problems. Due to these symptoms, gait abnormalities are common in MS, even in patients with low degrees of impairment [2]. Given the disease's progression, persons with MS (pwMS) are at a high risk of falling [3], with abnormal gait pattern as one of the disease's most prevalent impairment that affect gait stability and increase fall risk [4].  
The upper limbs play an important role in postural control and gait stability [5, 6]. Natural upper limb movements during walking in healthy persons lower the energeticcost of walking, facilitate leg movements [6] and enhance dynamic balance during locomotion [7] compared to when the upper limbs are not allowed to move or are moving in an altered coordination pattern. Affected arm swing movement and asymmetry during gait are common in neurological disorders such as Parkinson's disease (PD), even in early stages of the disease [8; 9] and in patients after stroke [10], which can affect their gait pattern [6]. Several papers have even acknowledged that upper extremity treatment enhances gait and normalizes arm swing, for various diagnoses such as PD [11], stroke [12] and juvenile idiopathic arthritis [13]. Considering the progression of unilateral and bilateral upper extremity dysfunction associated with disease severity in individuals with MS [14], it can be hypothesized that arm swing movements may be impacted during walking. Such alterations could potentially influence overall walking patterns and dynamic balance in pwMS.  
Studies on arm swing movements during gait in pwMS are scarce. A study found that pwMS walked slower and with decreased amplitude of elbow flexion compared to healthy control participants [15]. A recent study does indicate a preliminary link between upper limb function and balance in pwMS [16]. [PERSON] et al. researched arm swing during walking in pwMS, but their focus was specifically on dual-task assessment [17]. A separate study investigating the influence of upper extremity movements on balance during tandem walking in individuals with early-stage MS indicated that such movements may serve as an early marker for balance impairment in the progression of the disease [18]. During walking, pwMS may exhibit arm swing modifications that resemble those seen in people with PD, particularly in the early stages of the disease. These swing variations may be a sign of balance issues. This finding implies that changes in arm movement may indicate an onset of balance problems. This was, however, not investigated as such. More knowledge is needed on how these early alterations in arm swing can indicate the beginning and development of the disease because prior research has primarily concentrated on other motor symptoms or on more advanced stages of the disease. Comprehending these alterations in arm swing may offer a significant understanding of the wider range of motor function decline in pwMS, ultimately improving patient outcomes through early and focused therapy interventions. The innovative aspect of this study is examining changes in upper extremity movements in the early stages of MS and their potential importance as a predictive criterion.  
Therefore, the aim of the current study is to assess the arm swing during walking in pwMS shortly after their diagnosis in early MS. Additionally, we assess whether there are changes in the arm swing in the same pwMS in a short period (after three months). Finally, we will evaluate associations between the arm swing (changes) and functional mobility tasks which are related to balance and gait stability.