Assessment and rehabilitation of the upper limb after stroke have focused primarily on the contralesional arm. However, increasing evidence highlights functional sensorimotor alterations also in the ipsilesional arm. This study aims to evaluate the position sense of both arms after stroke using a passive position matching task. We hypothesized that the ipsilesional arm would have higher accuracy and precision than the contralesional arm but lower than the dominant arm in unimpaired participants. Additionally, we hypothesized a correlation in performance between the two arms in stroke survivors. The study included 40 stroke survivors who performed the proprioceptive test with both arms and 24 unimpaired participants who performed it with their dominant arm. During each trial, a planar robot moved their hand to a target and back. In the Participants had to indicate when their hand reached the target position in the second phase. We evaluated performance by computing the matching accuracy and precision. We found that the ipsilesional arm had similar matching accuracy but higher precision than the contralesional arm. Furthermore, only the matching accuracy of the two arms was correlated in the left and central regions of the workspace. When comparing stroke survivors to unimpaired participants, the ipsilesional arm exhibited significantly lower accuracy, yet not different precision. These findings support the notion that the ipsilesional arm is not ‘unaffected’ by stroke but rather ‘less-affected’, suggesting that stroke does not impact ipsilesional position sense precision. Additionally, the results suggest a dissociation between accuracy and precision in passive multi-joint position matching tasks.

Post stroke upper limb rehabilitation is a challenging problem with poor outcomes as 40% of survivors have functionally useless upper limbs. Robot-aided therapy (RAT) is a potential method to alleviate the effort of intensive, task-specific, repetitive upper limb exercises for both patients and therapists. The present study aims to investigate how a time matched combinatory training scheme that incorporates conventional and RAT, using H-Man, compares with conventional training toward reducing workforce demands. In a randomized control trial (NCT02188628, www.clinicaltrials.gov), 44 subacute to chronic stroke survivors with first-ever clinical stroke and predominant arm motor function deficits were recruited and randomized into two groups of 22 subjects: Robotic Therapy (RT) and Conventional Therapy (CT). Both groups received 18 sessions of 90 min; three sessions per week over 6 weeks. In each session, participants of the CT group received 90 min of 1:1 therapist-supervised conventional therapy while participants of the RT group underwent combinatory training which consisted of 60 min of minimally-supervised H-Man therapy followed by 30 min of conventional therapy. The clinical outcomes [Fugl-Meyer (FMA), Action Research Arm Test and, Grip Strength] and the quantitative measures (smoothness, time efficiency, and task error, derived from two robotic assessment tasks) were independently evaluated prior to therapy intervention (week 0), at mid-training (week 3), at the end of training (week 6), and post therapy (week 12 and 24). Significant differences within group were observed at the end of training for all clinical scales compared with baseline [mean and standard deviation of FMA score changes between baseline and week 6; RT: Δ4.41 (3.46) and CT: Δ3.0 (4.0); p < 0.01]. FMA gains were retained 18 weeks post-training [week 24; RT: Δ5.38 (4.67) and week 24 CT: Δ4.50 (5.35); p < 0.01]. The RT group clinical scores improved similarly when compared to CT group with no significant inter-group at all time points although the conventional therapy time was reduced to one third in RT group. There were no training-related adverse side effects. In conclusion, time matched combinatory training incorporating H-Man RAT produced similar outcomes compared to conventional therapy alone. Hence, this study supports a combinatory approach to improve motor function in post-stroke arm paresis. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT02188628.

Although motor and sensory impairments of the upper limb after stroke have been widely studied, the relationship between sensory deficits and motor functions has been less thoroughly explored. In this ongoing study, we investigated the relationship between proprioceptive impairments and motor functions with 20 chronic stroke survivors. Their proprioceptive abilities were assessed with a passive joint position matching test using H-Man and their motor functions were assessed with ARAT (Action Research Arm Test) and FMA (Fugl Meyer Upper Extremity Assessment) clinical scores. The assessments were conducted before, during and after the therapy. Results indicated a significant difference between the proprioceptive outcomes of healthy and stroke participants (at baseline) in both matching accuracy (absolute error, p=0.02) and precision (variability of the signed error, p=0.03). Significant correlations were found between the proprioceptive assessment outcomes (assessed before the beginning of the motor rehabilitation) of stroke participants with impaired proprioception and their ARAT clinical scores assessed at the first follow-up (week 12) (rho =- 0.74 and p=0.047 for the absolute error; rho =-0.78 and p= 0.03 for the variability of the signed error). The results from this preliminary study indicated a significant relationship between proprioceptive impairments and motor function performances in proprioceptively impaired chronic stroke participants.

Dyadic interaction between humans has gained great research interest in the last years. The effects of factors that influence the interaction, as e.g. roles or skill level matching, are still not well understood. In this paper, we further investigated the effect of skill level matching between partners on learning of a visuo-motor task. Understanding the effect of skill level matching is crucial for applications in collaborative rehabilitation. Fifteen healthy participants were asked to trace a path while being subjected to a visuo-motor rotation (Novice). The Novices were paired with a partner, forming one of the three Dyad Types: a) haptic connection to another Novice, b) haptic connection to an Expert (no visuo-motor rotation), or c) no haptic. The intervention consisted of a Familiarization phase, followed by a Training phase, in which the Novices were learning the task in the respective Dyad Type, and a Test phase in which the learning was assessed (haptic connection removed, if any). Results suggest that learning of the task with a haptic connection to an Expert was least beneficial. However, during the Training phase the dyads comprising an Expert clearly outperformed the dyads with matched skill levels. The results point towards the same direction as previous findings in literature and can be explained by current motor-learning theories. Future work needs to corroborate these preliminary results.