The effect of repeated measurements using an upper extremity robot on healthy adults

Kinematic parameters obtained with the ArmeoSpring for upper-limb assessment after stroke: a reliability and learning effect study for guiding parameter use

BACKGROUND

After stroke, kinematic measures obtained with non-robotic and robotic devices are highly recommended to precisely quantify the sensorimotor impairments of the upper-extremity and select the most relevant therapeutic strategies. Although the ArmeoSpring exoskeleton has demonstrated its effectiveness in stroke motor rehabilitation, its interest as an assessment tool has not been sufficiently documented. The aim of this study was to investigate the psychometric properties of selected kinematic parameters obtained with the ArmeoSpring in post-stroke patients.

METHODS

This study involved 30 post-stroke patients (mean age = 54.5 ± 16.4 years; time post-stroke = 14.7 ± 26.7 weeks; Upper-Extremity Fugl-Meyer Score (UE-FMS) = 40.7 ± 14.5/66) who participated in 3 assessment sessions, each consisting of 10 repetitions of the 'horizontal catch' exercise. Five kinematic parameters (task and movement time, hand path ratio, peak velocity, number of peak velocity) and a global Score were computed from raw ArmeoSpring' data. Learning effect and retention were analyzed using a 2-way repeated-measures ANOVA, and reliability was investigated using the intra-class correlation coefficient (ICC) and minimal detectable change (MDC).

RESULTS

We observed significant inter- and intra-session learning effects for most parameters except peak velocity. The measures performed in sessions 2 and 3 were significantly different from those of session 1. No additional significant difference was observed after the first 6 trials of each session and successful retention was also highlighted for all the parameters. Relative reliability was moderate to excellent for all the parameters, and MDC values expressed in percentage ranged from 42.6 to 102.8%.

CONCLUSIONS

After a familiarization session, the ArmeoSpring can be used to reliably and sensitively assess motor impairment and intervention effects on motor learning processes after a stroke. Trial registration The study was approved by the local hospital ethics committee in September 2016 and was registered under number 05-0916.

Test-Retest Reliability of Kinematic Assessments for Upper Limb Robotic Rehabilitation

Robot-measured kinematic variables are increasingly used in neurorehabilitation to characterize motor recovery following stroke. However, few studies have evaluated the reliability of these kinematic variables. This study aimed at evaluating the test-retest reliability of typically-used robot-measured kinematic variables in healthy subjects (HS) and patients with stroke (SP). Sixty-one participants (40 HS, 21 SP) carried out a planar robot-pointing task on two consecutive days. Nine robot-measured kinematic variables were computed: movement time (T), mean velocity (mV), maximal velocity (MV), smoothness error (SE), number of velocity peaks (nP), mean arrest period ratio (MAPR), normalized path length (NPL), root mean square error (RMS) from a straight line and the orthogonal projection of the last point of movement (LP). Intraclass Correlation Coefficients (ICC), percentage of the Standard Error of Measurement (SEM measured as a percentage of the mean value of the variable (%SEM)) and percentage of the Minimum Detectable Difference (MDD measured as a percentage of the mean value of the variable (%MDD)) were used to analyze the test-retest reliability of the kinematic variables. ICC scores for all kinematic variables were above 0.75 in both groups. %SEM values were below 10% except for MAPR (13.4%) in HS and nP, MAPR and RMS in SP (13.0%, 11.7% and 15.2% respectively). %MDD values were higher for RMS in SP (42.1%) and MAPR in HS (37.1%) and lower for LP (1.6% in HS and 8.1% in SP). The nine robot-measured kinematic variables all demonstrated good reliability, with high ICC values (>0.75) and an acceptable level of measurement error (%SEM< 16%). However, 3/9 robot-measured kinematic variables, did not appear to be sufficiently sensitive to change (%MDD>30%) to be considered useful in patients with stroke.

Compensation for the intrinsic dynamics of the InMotion2 robot

The InMotion2 and other similarly designed robots, are commonly used for rehabilitation of neurological injuries and motor adaptation studies. These robots are used to simulate haptic environments; however, anisotropy in end-point impedance due to the intrinsic robot dynamics can compromise these experiments. The goal was to decrease the magnitude and anisotropy of the robot impedance using a dynamic compensation algorithm that reduces the forces normally felt by the user during rapid movements. We tested this algorithm with two different methods for real-time calculation of derivatives, a novel quadratic fit method (CQF) and the commonly used backward derivative method (CBD). Six subjects performed a series of point-to-point movements under three conditions (no compensation, CQF, CBD), in different directions at peak speeds of 50, 100 and 150 cm/s. Without compensation, tangential peak-to-peak forces were as large as 69 N in certain directions at the 150 cm/s speed. Both CQF and CBD significantly reduced tangential forces in all directions and speeds. CQF outperformed CBD in the directions with highest intrinsic impedance, reducing tangential forces by 64% in these directions. Compensation also significantly reduced forces normal to the movement direction, with CQF again outperforming CBD in several cases. Anisotropy was assessed by the range of tangential peak-to-peak forces across movement directions. In the no compensation condition, anisotropy was as high as 52.7 N at the 150 cm/s speed, but an average anisotropy reduction of 74% was achieved with CQF. The CQF method can significantly reduce impedance and anisotropy in this class of robot.

Effect of gravity on robot-assisted motor training after chronic stroke: a randomized trial

OBJECTIVES

To determine the efficacy of 2 distinct 6-week robot-assisted reaching programs compared with an intensive conventional arm exercise program (ICAE) for chronic, stroke-related upper-extremity (UE) impairment. To examine whether the addition of robot-assisted training out of the horizontal plane leads to improved outcomes.

DESIGN

Randomized controlled trial, single-blinded, with 12-week follow-up.

SETTING

Research setting in a large medical center.

PARTICIPANTS

Adults (N=62) with chronic, stroke-related arm weakness stratified by impairment severity using baseline UE motor assessments.

INTERVENTIONS

Sixty minutes, 3 times a week for 6 weeks of robot-assisted planar reaching (gravity compensated), combined planar with vertical robot-assisted reaching, or intensive conventional arm exercise program.

MAIN OUTCOME MEASURE

UE Fugl-Meyer Assessment (FMA) mean change from baseline to final training.

RESULTS

All groups showed modest gains in the FMA from baseline to final with no significant between group differences. Most change occurred in the planar robot group (mean change ± SD, 2.94 ± 0.77; 95% confidence interval [CI], 1.40-4.47). Participants with greater motor impairment (n=41) demonstrated a larger difference in response (mean change ± SD, 2.29 ± 0.72; 95% CI, 0.85-3.72) for planar robot-assisted exercise compared with the intensive conventional arm exercise program (mean change ± SD, 0.43 ± 0.72; 95% CI, -1.00 to 1.86).

CONCLUSIONS

Chronic UE deficits because of stroke are responsive to intensive motor task training. However, training outside the horizontal plane in a gravity present environment using a combination of vertical with planar robots was not superior to training with the planar robot alone.

Recovery of submaximal upper limb force production is correlated with better arm position control and motor impairment early after a stroke

OBJECTIVE

This study determined whether recovery of upper limb position control using submaximal force production correlates with an improvement in functional arm impairment during early recovery from stroke.

METHODS

Ten consecutive inpatients were recruited from a stroke unit. Each patient was in early recovery (<8 weeks post-lesion) from their first ever stroke. Evaluations of submaximal continuous force production and position control, maximal force production at the shoulder and a clinical outcome measure of motor impairment (Fugl-Meyer score; FM) were performed 20 days post-stroke as a baseline and then once a week for the following four weeks.

RESULTS

Submaximal force production and its modulation during a position-holding task improved in early recovery after stroke, whereas maximal force production did not. Better modulation of submaximal force production enabled improved arm position control which was significantly correlated to the changes in FM score of motor impairment during recovery.

CONCLUSIONS

This study demonstrated that improvement in submaximal force modulation can operate as a mechanism enabling better motor behaviour such as arm position control during early recovery from a stroke.

SIGNIFICANCE

Future rehabilitation strategies may benefit from adding submaximal force development and modulation to early interventions after stroke.