Upper limb contribution during tandem gait in multiple sclerosis: An early marker of balance impairments.

Tandem gait is widely used during clinical exams to evaluate dynamic balance in chronic diseases, such as multiple sclerosis (MS). The early detection of balance impairments in MS is challenging to improve the understanding of patients' complaints. The objective was to propose two indexes to quantify the contributions and inefficiency of limb and trunk movements during tandem gait in early-stage MS patients. Fifteen patients with remitting-relapsed MS, with a median Expanded Disability Status Scale of 2.5 [0-4] were compared to 15 matched healthy participants. Three-dimensional motion analysis was performed during tandem gait to calculate spatiotemporal parameters, contribution and inefficiency indexes, based on the linear momentum of body segments. Compared to healthy participants, MS patients at the early stage of disease executed tandem gait with higher speed (p = 0.03) and increased step length (p = 0.03). The contribution indexes of upper limbs were significantly decreased during swing phase in MS patients. The inefficiency index for the upper limbs were around twice higher for MS patients compared to healthy participants. Since the additional movements concerned only light body segments and not contribute to the whole-body forward progression during tandem gait, they could reflected more both upper limb movements alterations and restoring movements to avoid loss of balance during tandem gait around swing phase in MS. These quantified indexes could be used as physical markers to quantify both the balance deterioration and the efficiency of rehabilitation program during the follow up of MS from the early stage of their disease.

A new approach of the Star Excursion Balance Test to assess dynamic postural control in people complaining from chronic ankle instability.

The purpose of this study was to quantitatively and qualitatively assess dynamic balance with accuracy in individuals with chronic ankle instability (CAI). To this aim, a motion capture system was used while participants performed the Star Excursion Balance Test (SEBT). Reached distances for the 8 points of the star were automatically computed, thereby excluding any dependence to the experimenter. In addition, new relevant variables were also computed, such as absolute time needed to reach each distance, lower limb ranges of motion during unipodal stance, as well as absolute error of pointing. Velocity of the center of pressure and range of variation of ground reaction forces have also been assessed during the unipodal phase of the SEBT thanks to force plates. CAI group exhibited smaller reached distances and greater absolute error of pointing than the control group (p<0.05). Moreover, the ranges of motion of lower limbs joints, the velocity of the center of pressure and the range of variation of the ground reaction forces were all significantly smaller in the CAI group (p<0.05). These reduced quantitative and qualitative performances highlighted a lower dynamic postural control. The limited body movements and accelerations during the unipodal stance in the CAI group could highlight a protective strategy. The present findings could help clinicians to better understand the motor strategies used by CAI patients during dynamic balance and may guide the rehabilitation process.