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Table 3 Summary of studies that compared EA to ER

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)

Bouchard et al. [61]

Randomized comparative experiment.

Trial not registered.

34 in total

EA group: 17 haptic guidance (ER) group: 17

ER group: age (mean) = 67 ± 7, months since stroke (mean) = 63 ± 54 AMFMa = 63 ± 8

EA group: age (mean) = 67 ± 6, months since stroke (mean) = 78 ± 64 AMFM = 60 ± 10

TEO, a robotic device with 10-degree flexion/ extension of the left/ right wrist, actuated by Dynamixel MX-106 servomotor

Experimental task: flex paretic wrist at the right time.

ER group:

the robotic device adjusted its activation time to reduce the timing errors (k value decreased by 90%).

EA group: the opposite, the timing errors were increased (k value increased by 90%)

Training parameters: Four phases of baseline assess-ment (140 trials) before the intervention. 75 trials during the inter-vention, and 40 trials at the reten-tion phase.

Kinematic:

Absolute timing errors (ms)

A significant decrease of 1.1 ± 5.1 ms in absolute timing errors in the ER group (p = 0.032), and a non-significant increase of 0.4 ± 6.0 in the EA group (p = 0.45).

A between group comparison revealed no significant difference between the two groups (95% confidence interval: − 1.2 to 4.3)

0.27 (small effect size)

8/10, high quality

Cesqui et al. [58]

Crossover design.

Trial not registered

15 in total

EA group: 6

ER group: 9

(before cross-over)

Ages: 20–71 years (mean = 42 ± 17) 8 males and 7 females, all participants suffered from stroke (stages unknown) CMb: First EA group: mean = 5 ± 0.89

First ER group: mean = 4 ± 0.86

InMotion2

Experimental tasks: reaching targets in a plane.

EA group: received divergent field (negative elastic force)

ER group: received active assistance

Training parameters:

One hour per session, ten sessions per therapy cycle which lasted two weeks before subjects switched groups.

Kinematic:

Metric indexes (movement smoothness, movement accuracy, path length ratio, movement direction variability)

Clinical: MSSc, MASd, ROM Shoulder and Elbow

MAS: in the first cycle, ER showed more improvement than EA (3.5 ± 2.8 vs 1.8 ± 3.6), but level of significance not provided.

In the second cycle, ER still showed more improvement than EA (0.9 ± 3.5 vs 0.3 ± 2.7), but level of significance not provided.

MSS: in the first cycle, ER showed more improvement than EA (2.9 ± 7.1 vs 1.8 ± 5.2), but level of significance not provided.

In the second cycle, ER still showed more improvement than EA (1.0 ± 4.8 vs 0.6 ± 6.4), but level of significance not provided.

ROMs: no significant changes (numerical values not provided)

Metric indexes: no numerical values reported, so unable to calculate differences between groups. The authors reported final metric indexes differences were not significant in the group started with EA (F = 1.61, p = 0.194) but in the group started with ER, there was a significant improvement indexes (F = 9,46, p = 0.006). They did not mention the comparison of metric indexes between groups.

MAS: first cycle 0.53 (medium effect).

second cycle 0.19 (very small effect).

MSS: first cycle 0.18 (very small effect).

second cycle 0.09 (very small effect).

3/10, poor quality

Patton et al. [24]

Quasi-experimental design.

Trial not registered

31 in total,

Stroke Group EA = 9

ER = 9

C = 9

Healthy Group

EA = 2

ER = 2

Ages = 30–72 years (EA: mean = 54.3 ± 8.8;ER: mean = 48.0 ± 8.4;Control: mean = 51.2 ± 6.1), besides 4 healthy subjects, all participants suffered from a chronic stroke (16–173 months, EA: mean = 69.1 ± 50.2; ER: mean = 109.3 ± 45.8; Control: mean = 70.8 ± 60.4), FM: EA group mean = 40.2 ± 13.7

ER group mean = 25.5 ± 10.9

Control group mean = 37.3 ± 16.2

Free-extremity robot with two degrees of freedom. The participant’s arm was supported by a low-friction, low-impedance mechanism

Experimental tasks: reaching

EA group: both stroke and healthy EA groups received force field that magnified errors (EA)

ER group: both stroke and healthy ER groups received force field that reduced error. In the stroke control group, the 9 participants with stroke did not receive interfering forces.

Training parameters:

One single session of 834 movements.

Kinematic: initial direction error (degrees). Adaptation capacity

The stroke EA group showed improvement at initial direction error (8.9 ± 10.9) while the stroke ER group showed deterioration (− 6.8 ± 9.6). The different between EA and ER groups was significant [F(1,13) = 4.29, p < 0.001].

Stroke subjects showed less adaptation capacity than healthy subjects (26% less)

Initial direction error: 1.53 (very large effect)

1/10, poor quality

Tropea et al. [54]

Crossover randomized controlled trial.

Trial not registered

18 in total

EA = 9

ER = 9 (before cross-over)

Ages: 21–71 (EA: mean = 49.7±

18.7; ER: mean = 44.9 ± 15.9), 9 males and 9 females, all participants suffered from a chronic stroke (mean/SD unknown), CM: First EA group: mean = 4.9 ± 0.9

First ER group: mean = 4.2 ± 1.0

InMotion2 robotic system

Experimental tasks: reaching targets in a plane.

EA group: received divergent force field

ER group: received active assist during practice

Training parameters:

Two weeks of training per cycle, and two cycles in total. After each cycle, subjects switch groups.

Kinematic: the trajectory of the end-effector

Clinical:

MAS, MSS

MAS: in the first cycle, ER group showed more improvement than EA (2.9 ± 3.2 vs 1.2 ± 3.2), but not significantly.

In the second cycle, ER group still showed more improvement than EA (1.4 ± 1.2 vs 0.7 ± 2.3), but not significantly.

MSS: in the first cycle, ER group showed more improvement than EA (2.2 ± 2.0 vs 0.8 ± 3.5), but not significantly.

In the second cycle, ER group still showed more improvement than EA (1.4 ± 1.3 vs 1.1 ± 1.1), but not significantly.

Trajectory of end-effector: no numerical values reported, but authors stated that EA group had significantly straighter (p = 0.028) as well as smoother (p = 0.031) trajectory than ER group

MAS: first cycle 0.53 (medium effect)

Second cycle 0.40 (small effect)

MSS: first cycle 0.51 (medium effect)

Second cycle 0.25 (small effect)

6/10, high quality

  1. aAMFM: Arm Motor Fugl-Meyer
  2. bCM: Chedoke-McMaster scale score
  3. cMSS: Motor Status Score
  4. dMAS: Modified Ashworth Scale