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Table 1 Summary of studies that compared EA to training without error modification

From: The effects of error-augmentation versus error-reduction paradigms in robotic therapy to enhance upper extremity performance and recovery post-stroke: a systematic review

Article Study design Number of participants: experimental group (E) and control group (C) Participants characteristics Equipment Experimental Protocol Outcomes and assessment tools Main results and interpretation
(means ± standard deviation)
Effect size (Cohen’s d) Quality of study (PEDro score)
Abdollahi et al. [52] Crossover randomized controlled trial.
Trial registered NCT01574495
27 in total, E = 13, C = 14 (before crossover) Ages: 36–88 years (mean = 57.92 ± 9.96), 12 males and 15 females, all participants suffered a single cortical or subcortical stroke at least 6 months prior to the study (mean = 82.34 ± 72.04 months, 9 hemorrhagic, 18 ischemic) FMb scores: 15–50 (mean/SD unknown) Virtual Reality Robotic and Optical Operations Machine (VRROOM). Phantom Premium 3.0 robot. Experimental task: various reaching movement
Control group: received only treatment of repetitive practice
EA group:
same as the control group in addition of combined visual and haptic error augmentation
Training parameters:
60 min per session, three sessions per week, two weeks of training per phase (two). After first phase, all subjects switched to the other group.
Clinical
ROMc, AMFMa, WMFT FASd, WMFT time measure, Box and Blocks test
ROM: no significant effects AMFM: in the first phase, EA showed more improvement than control (2.08 ± 2.25 vs 0.69 ± 2.90), and this difference was significant [F(1,24) = 4.261, p < 0.05]
In the second phase, EA was still better than control (1.15 ± 2.21 vs 0.54 ± 2.30), but not significantly (numerical values not provided)
WMFT FAS: in the first phase, EA was better than control (0.11 ± 0.24 vs 0.01 ± 0.16), but level of significance unknown.
In the second phase, control was better than EA (0.14 ± 0.22 vs − 0.02 ± 0.25), but level of significance unknown.
WMFT time: in the first phase, EA was better than control (1.48 ± 8.86 vs − 0.53 ± 5.19), but level of significance unknown.
In the second phase, EA was better than control (1.19. ± 5.68 vs 0.17 ± 8.02), but level of significance unknown.
Box and Blocks test: no significant effects
AMFM:
first phase 0.53 (medium effect).
second phase 0.27 (small effect).
WMFT FAS:
first phase 0.51 (medium effect).
second phase 0.52 (medium effect)
WMFT time:
First phase
0.28 (small effect)
Second phase 0.14 (very small effect)
7/10, high quality
Givon-Mayo et al. [63] Pilot study.
Trial registered
NCT02017093
7 in total, E = 4 and C = 3 Ages: 45–78 (mean = 59.14 ± 9.77), 8 males and 1 female. All participants sustained a stroke (1 hemorrhagic, 8 ischemic) 2 to 3 weeks prior to the study. FM scores: EA group mean = 53.25 ± 3.77
Control group
mean = 54.33 ± 3.84
DeXtreme prototype robot- 2 degrees of freedom. Free end Robot. Experimental tasks: reaching
EA group: received error inducing forces from the robot
Control group: also attached to the robot, but did not receive forces
Training parameters:
20 min per session, three sessions per week for five weeks
Kinematic: movement velocity deviation error (cm/sec).
Clinical: FM, MASe
MAS: the EA group showed more improvement than the control group (3.2 ± 2.6 vs 1.7 ± 3.2), but the level of significant unknown
FM: no significant changes
Velocity deviation error: the EA group showed significant (p < 0.05) more improvement than the control group (− 16.8 ± 3.8 vs − 4.7 ± 3.8)
MAS: 0.51 (medium effect)
Velocity deviation error:
3.2 (very large effect)
3/10, poor quality
Huang and Patton [59] Crossover design.
Trial not registered
30 in total, Participants were randomly assigned to either one control group or two experimental groups, but the numbers are unknown. Mean age = 52.0 ± 8.2, all participants suffered from a chronic stroke (mean = 102.0 ± 84.0 months). Clinical assessment results prior to the study were not available A planar force feedback device. The subject’s arm was supported by a low-friction, low-impedance mechanism Experimental tasks: circular movement task
Control group practiced on the training device in null-field conditions in all sessions.
The two experimental groups: trained in a null field condition in the first session, then received either EA force alone or EA force combined with positive limb inertia in the next session. They switched to the other condition in third session
Training parameters:
Two hours per session, three sessions in total
Kinematic: radial deviation (distance between the handle and template circular track) (mm) When evaluated in the next session, the control showed no significant improvement (0.7 mm ± 2.3, 95% confidence interval: − 0.4 to 1.8). The EA group showed the largest significant improvement (1.4 ± 2.7, CI: 0.2 to 3.0) while the combined EA with inertia group showed non-significant improvement (1.1 ± 2.7, CI: 0 to 2.2) EA compared to control: 0.28 (small effect).
EA compared to combined EA with inertia: 0.11 (very small effect)
3/10, poor quality
Majeed et al. [62] Randomized comparative experiment.
Trial not registered.
28 in total, participants were randomized into experimental and control groups based on blocks of FM scores Ages: 26–78 (mean = 55.38, SD unknown), 17 males and 11 females, all participants suffered from a cortical chronic stroke (mean/SD unknown), Upper extremity FM score: 25–49 (block randomized into both groups, mean/SD unknown) Three-dimentional haptic/ graphic system called the Virtual Reality Robotic and Optical Operations Machine (VRROOM) Experimental tasks: reaching
Control group: received only treatment of repetitive practice
EA group:
same as the control group in addition of combined visual and haptic error augmentation
Training parameters:
45 min per session, three sessions per week, two weeks of training
Clinical:
AMFM
At the end of 2 weeks of training, no significant difference was found between EA and control groups in improvement of AMFM (numerical data not provided).
At one-week follow-up, EA group showed more retention than control group (2.60 ± 3.50 vs − 0.1 ± 6.98), but the level of significant known
From the end of training to one-week follow-up:
0.52 (medium effect)
6/10, high quality
Patton et al. [53] Randomized controlled trial.
Trial not registered
15 in total. E = 12, C = 9 (6 subjects returned for a second visit, so they served as their own control) Ages: 30–76 (E: mean = 50.66 ± 13.08;
C: mean = 50.77 ± 12.16), 9 males and 6 females, all participants suffered from a chronic stroke (E: mean = 77.25 ± 40.85 months;
C: mean = 99.89 ± 44.13) prior to the experiment. FM score (E: mean = 34.36 ± 12.23; C: mean = 35.0 ± 11.79
A two degrees-of-freedom robot Experimental tasks: reaching EA group: received EA forces from the robotic while doing repetitive practice.
Control group: Same training but without EA forces.
Training parameters:
One single session of three hours and consisted of 744 movements
Kinematic: size of movement error (change in %) Clinical:
AMFM
AMFM: the EA group had a greater improvement than control group (1.6 ± 2.6, p = 0.06 vs 0.4 ± 1.1, p > 0.27), but the results were not significant
Movement error size: the EA group had a greater improvement than control group (− 45.2 ± 80.6 vs − 11.1 ± 48), but the levels of significance unknown
AMFM: 0.65 (medium effect)
Movement error size: 0.53 (medium effect)
5/10, fair quality
Rozario et al. [60] Crossover design.
Trial not registered
10 in total
Stroke group (before cross-over)
EA = 3
Control = 2
Healthy group 5
Stroke: ages: 36–69 (mean = 55.0 ± 12.1), 4 males and 1 female, suffered a single cortical stroke for more than 6 months (mean/SD unknown), AMFM:
EA group mean = 35.33 ± 8.14
Control group mean = 43.50 ± 2.12
Healthy: ages: 19–27 (mean/SD unknown)
A 6-degree of freedom PHANTOM Premium 3.0 robot Experimental tasks: various reaching movement.
Control group: received only treatment of repetitive practice
EA group:
same as the control group in addition of combined visual and haptic error augmentation
Healthy group: did not receive any treatment, only data collected
Training parameters:
40 min per session, three sessions per week, and two weeks per phase (two). After first phase, all subjects switched groups.
Kinematic: ROM errors (m)
Clinical:
AMFM, WMFT FAS, WMFT time, Box and Blocks test
Clinical test: no noticeable changes in any of the clinical tests (numerical data not provided).
ROM errors: In the first phase, EA showed more improvement than control group (0.08 ± 0.08 vs 0.04 ± 0.04), level of significant unknown.
In the second phase, EA showed no improvement but control group showed deterioration (0 ± 0 vs − 0.02 ± 0.03).
More errors seen in stroke subjects than healthy subjects.
ROM errors: first phase 0.75 (medium effect).
Second phase 1.05 (large effect)
4/10, fair quality
  1. aEA/ER: error augmentation/error reduction
  2. bFM/AMFM: Fugl-Meyer assessment/Arm Motor Fugl-Meyer
  3. cROM: Range of motion
  4. dWMFT FAS: Wolf motion function test-functional ability scale
  5. eMAS: Motor Assessment Scale