Effectiveness of different extrinsic feedback forms on motor learning in children with cerebral palsy: a systematic review

Figures & data

Figure 1. Visual display of different forms of extrinsic feedback.

Tree figure depicting varying forms of extrinsic feedback, divided into the following categories: modality, focus, specificity, timing, frequency, and level of guidance.

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Tree figure depicting varying forms of extrinsic feedback, divided into five categories, shown in squares. It starts with modality of the feedback: auditory, visual, sensory or verbal. From verbal feedback, an arrow leads to the next square holding further specifications of verbal feedback. These are: the focus of the feedback (that is, knowledge of performance versus knowledge of results feedback), and the level of specificity of the feedback (that is, quantitative versus qualitative feedback). From this square, three arrows lead to the last three squares aligned vertically underneath each other, each holding one category. The upper square holds “Timing”, that is, concurrent versus terminal feedback. The middle square holds Frequency, that is, 100% versus less than 100% feedback. Under the latter, four bullet points show four manners of reducing the feedback frequency, namely: faded, summative slash averaged, performance based-bandwidth, and self-controlled feedback. The lower and final square holds the level of guidance, that is, prescriptive versus descriptive feedback. Underneath the latter are two bullet points, showing two options with regard to the informational content of the descriptive feedback, that is, correct aspects information versus error information.

Figure 2. Flow chart depicting the process of inclusion of studies.

PRISMA flow chart displaying the process of search and selection of included studies. From 404 records coming out of the initial search, 12 studies were ultimately included in this review.

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This flow chart shows the process of search and selection of included studies, following the PRISMA guidelines. Firstly, 401 records were identified through database searching, and three additional records were identified through other sources. After duplicates were removed, 358 records remained, which were all screened. Two hundred eighty-nine records were excluded, based on title and abstract. The remaining 69 articles were assessed for eligibility based on full-text versions. In this process, 57 articles were excluded for several reasons. Of these excluded articles, 30 concerned biofeedback; 6 articles concerned mirror therapy; 7 articles made no comparison between modalities or frequencies, or between samples of typically developing children and children with cerebral palsy; 9 articles only examined motor performance, and not motor learning; 5 articles examined adults, and not children with cerebral palsy. Ultimately, 12 studies were included in our qualitative synthesis.

Table 1. Extracted details of the included studies applying knowledge of results feedback.

Author, year	Sample characteristics	Study design	Intervention/Task	Movement characteristics	Outcome measures	Assessment time points	Feedback provided	Feedback delivery schedule	Results
Hemayattalab et al. 2013 [36]	20 CP (0% female), aged 7–12, spastic hemiplegia, GMFCS level I-III, MACS level not reported.	RCT	Throwing a bean bag (100 g) overhead, blind-folded, towards a circular 10 cm radius/20 cm diameter target, 3 m away. 80 trials. Transfer: 4 m away.	Upper extremity, aiming, gross motor coordination, complex.	Accuracy, (AU). Higher score is better (closer to the target center).	Pre-test, post test, retention test (24 h), transfer test (24 h).	KR (verbal): placement of bean bag landing (near/far, left/right, short/long).	Group 1: self-controlled KR frequency. Group 2: yoked^a KR frequency.	Group 1 and 2 were not stat. different at posttest. At retention and transfer test, group 1 performed better than group 2 (r = .89 and r = .95**).
Burtner et al., 2014 [32]	19 children with CP (52.6% female), aged 8–16 years, spastic hemiplegia, MACS level I-III. 20 TD children (40% female), aged 8–14 years.	Quasi controlled trial	Moving a lever to replicate a target trajectory, shown at the beginning of each trial (for 2000 ms). 200 trials (4 sessions of 5 10-trial blocks).	Upper extremity (single-handed), fine motor coordination, discrete, simple.	Accuracy (root mean square error (RMSE))	Pretest, post test, retention test, reacquisition test	KR (visual): RMSE. KP (visual): graphic representation of participant's trajectory.	Group 1 (CP): feedback 100%. Group 2 (TD): feedback 100%. Group 3 (CP): faded feedback, each session −25% (total: 62%). Group 4 (TD): faded feedback, each session −25% (total: 62%).	Pretest - posttest: all groups improved, no group*feedback interaction. Retention test: no group*feedback interaction. Reacquisition: all groups reached their best score from the acquisition phase.
Hemayattalab, 2014 [40]	22 students with CP (0% female), 12.26 ± 3.11 years old, left-side hemiplegia, GMFCS level and MACS level not reported.	Quasi controlled trial	Dart throwing towards the center of a target, 205 cm away. 5 sessions of 4 blocks*5 trials.	Upper extremity, aiming, fine motor coordination, complex.	Target score: center = 10 points, each peripheral band −1 point. Outside of all bands = 0 points.	Post tests (end of each session), retention test (24 h), transfer test (target 300 cm away; 24 h).	KR (visual): placement of dart on target.	Group 1: self-controlled KR after 50% of the trials. Group 2: instructor-controlled KR after 50% of good and bad trials. Group 3: no KR.	Group 1: bigger improvement prepost test (effect size r = .55**), pretest-retention (effect size r = .51**), pretest-transfer (effect size r = .56**) compared to group 2 and 3. No difference between group 2 and 3.
Harbourne, 2001 [34]	10 adolescents with CP (60% female), aged 13–18 years, spastic hemi-(n = 3)/di-(n = 4)/quadriplegia(n = 3), GMFCS level I-IV, MACS level not reported. 10 TD adolescents (40% female), aged 13–18 years.	Quasi post test only design	Move lever along slide in 150 ms and guess their own movement time. 80 trials in two days.	Upper extremity (single-handed), fine motor timing, simple.	Speed error (ms), error detection (ms).	Retention test (without KR, trials 51–60).	KR (verbal): movement time (ms).	Group 1(CP) and 2 (TD): KR after trials 1–10, 21–50 (day 1), 61–80 (day 2). No KR after trials 11–20 (day 1), 51–60 (day 2).	Group 2: lower speed error (effect size d = 1.02**) and better error detection (effect size d = 1.46**) than group 1. However, wide variability within group 1 scores, with some scoring within the range of group 2.
Hemayattalab and Rostami, 2010 [35]	24 CP (sex ratio not reported), aged 7–15, spastic hemiplegia, GMFCS level and MACS level not reported.	Quasi controlled trial	Dart throwing towards the center of a target, 205 cm away. 8 sessions of 6 blocks*5 trials.	Upper extremity, aiming, fine motor coordination, complex.	Accuracy (AU). Higher score is better (closer to the center).	Pretest, acquisition test/posttest, retention test (72 h)	KR (visual): placement of dart on target, numeric.	Group 1: 100% KR. Group 2: 50% KR. Group 3: 0% KR.	Group 1, 2, and 3 improved pretest-acquisition test (r = .99 **; r = .98; r = .94) and pretest-retention test (r = .84; r = .96; r = .91**). Group 1 scored better than the other groups pretest-acquisition (r = .84**). Group 2 scored better at pretest-retention than group 1 (r = .73**) and group 3 (non-significant).
Valvano and Newell, 1998 [39]	8 CP (% female), aged 7–12 years. Spastic diplegic/quadriplegic. GMFCS and MACS levels not reported. 8 age-matched TD children.	Quasi controlled trial	Pinch grip force matching of 20% MVC. 12 block of 6 trials, 5 s per trial	Upper extremity (single-handed), fine motor control, simple.	Accuracy (RMSE and AE), variability (coefficient of variation (CV))	Pretest, post test, retention (5 days)	KR (visual): forces produced relative to a stationary target.	CP group and TD group: KR in 50% of the trials, counterbalanced across participants.	Acquisition: Both groups improved, but TD improved significantly more in RMSE, AE and CV than CP group. Retention: No significant differences compared to acquisition level.

Table 2. Extracted details of the included studies applying knowledge of performance feedback.

Author, year	Sample characteristics	Study design	Intervention/Task	Movement characteristics	Outcome measures	Assessment time points	Feedback provided	Feedback delivery schedule	Results
Baram and Lenger, 2011 [31]	14 patients with CP (61.5% female), aged 5–26 years. Type and GMFCS level unknown. 8 able-bodied controls (50% female), aged 12–14.	Quasi controlled trial	Walking a 10 m track (20 min training).	Lower extremities, postural control, gross motor coordination, complex.	Walking speed (m/s), stride length (m)	Pretest, post test	KP (visual): transverse lines projected through glasses, based on participant's motion. Steps should be placed in between lines. KP (auditory): clicking sound in response to step.	Group 1 (CP): KP (visual). Group 2 (TD): KP (visual). Group 3 (CP): KP (auditory). Group 4 (TD): KP (auditory). All groups were provided with KP throughout the whole training session.	Group 1 improved stride length more than (effect size d = 1.58**) and walking speed comparably to group 2. Group 3 improved walking speed (effect size d = 1.15**) and stride length (effect size d = 1.41**) more than group 4. No differences in magnitude of improvement between group 1 and 3.
Burtner et al., 2014 [32]	19 children with CP (52.6% female), aged 8–16 years, spastic hemiplegia, MACS level I-III. 20 TD children (40% female), aged 8–14 years.	Quasi controlled trial	Moving a lever to replicate a target trajectory, shown at the beginning of each trial (for 2000 ms). 200 trials (4 sessions of 5 10-trial blocks).	Upper extremity (single-handed), fine motor coordination, discrete, simple.	Accuracy (root mean square error (RMSE))	Pretest, post test, retention test, reacquisition test	KP (visual): graphic representation of subject's trajectory. Additional KR (visual): RMSE	Group 1 (CP): feedback 100%. Group 2 (TD): feedback 100%. Group 3 (CP): faded feedback, each session −25% (total: 62%). Group 4 (TD): faded feedback, each session −25% (total: 62%).	Pretest – post test: all groups improved, no group*feedback interaction. Retention test: no group*feedback interaction. Reacquisition: all groups reached their best score from the acquisition phase.
Hamed and Abd-elwahab, 2011 [33]	30 children with CP (43.3% female), aged 6–8 years, spastic (1 − 1+ on the MAS), hemiparetic. GMFCS level not reported.	RCT	Gait training (7 different walking activities). 3 sessions per week for 3 months.	Lower extremities, postural control, gross motor coordination, complex	Walking velocity (m/s), stride length (m), cadence (step/min), cycle duration (s).	Pretest, post test	KP (auditory): during all walking activities, music based on walking speed, stride length, cadence.	Group 1: KP throughout all training sessions. Group 2: no augmented feedback.	Group 1: improved walking velocity (effect size d = 3.29**), stride length (effect size d = 2.90**), cadence (effect size d = 3.24**) and cycle time (effect size d = 1.57**) compared to group 2.
Hussein et al., 2019 [37]	30 children with CP (50% female), aged 4–6 years, spastic (1–1+) diplegic, GMFCS II-III.	Quasi controlled trial	Gait training, 3*30 min a week for two months	Lower extremities, postural control, gross motor coordination, complex.	Spatial parameters (step length, step width, foot angle), temporal parameters (cadence, gait velocity, gait time), kinetic parameters (max force, max peak pressure)	Pretest, post test	KP (visual): appearing image of 7 pressure points of the foot	Group 1: KP (visual) throughout all training sessions. Group 2: no augmented feedback.	Group 1 improved significantly more than group 2 in spatial parameters (step length d = .781**, step width d = .803**, foot angle d = 1.228**) and temporal parameters (cadence d = .828**, gait velocity d = .794**, gait time d = .765**), but not in kinetic parameters.
Talbot and Junkala, 1981 [41]	59 CP (45.8% female), aged 7–21 years (mean age: 14.25 years), spastic (84%). MACS level not reported.	RCT	Line tracing task. 40 trials. 2 per day; 20 training days.	Upper extremity, fine motor coordination, complex	Accuracy (through Motor Accuracy Test (SCMAT)), accuracy adjusted for speed	Pretest, post test, retention test (3 months)	KP (auditory, concurrent): buzzer sounds when deviating from black tracing line	Group 1: KP at each trial. Group 2: no KP. Group 3: no practice, only tests.	Post test: Group 1 performed better than group 2 and 3. Retention test: trend - Group 1 performed better than group 1 and 3. For speed-corrected accuracy: only trends in favor of group 1.
Thorpe and Valvano, 2002 [38]	13 children with bilateral CP (61.5% female), aged 6–12 years, GMFCS level III, diplegia (n = 9) and quadriplegia (n = 4)	RCT	Moving a therapeutic vehicle (Pedalo) backwards along a 6.4 m line by shifting weight and alternately extending the legs. 28 trials (7 blocks of 4*10 s trials)	Lower extremities, postural control, gross motor coordination, complex	Backward displacement (cm)	Pretest, 48 h retention test (both 1 block of 4 trials).	KP (verbal): every other trial, based on 6 common constraints. KP + CS (verbal): feedback coupled to one of the 6 model movement pictures for mental imagery.	Group 1: block 1 none, block 2 KP, block 3–7 KP + cognitive strategy (CS). Group 2: block 1–2 none, block 4–5 KP, block 6–7 KP + CS. Group 3: block 1–3 none, block 4–6 KP, block 7 KP + CS.	8/13 participants were unable to learn the task. 4 participants improved through practice without feedback, 1 participant improved most with KP, 3 participants improved most with KP + CS.

^aA yoked feedback scheme can be used in a control group in studies where the effects of self-controlled feedback frequency are investigated. The participants in the intervention group get to determine how often and after which trials they receive feedback. The yoked group cannot determine when and how often they receive feedback. They are provided with feedback at the same frequency at which the intervention group, on average, has asked for feedback.

*Effect size available from the cited publication.

**Effect size computed from publication data.

Figure 3. Results of risk-of-bias assessment for each study. Green = low risk of bias; red = high risk of bias; yellow = some concerns.

Results of the risk of bias assessment per study for each of the five domains, and the overall risk of bias. One study, from Hamed and Abd-elwahab, has a low overall risk of bias; six studies have a high overall risk of bias; and five studies have some concerns.

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These are the results of the Risk of Bias assessment per study for each of the five domains, and the overall risk of bias. Baram and Lenger, 2011. Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: some concerns. Selection of the reported result: some concerns. Overall: some concerns. Burtner and alia, 2014. Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: low risk. Selection of the reported result: low risk. Overall: some concerns. Hamed and Abd-elwahab, 2011. Randomization process: low risk. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: low risk. Selection of the reported result: low risk. Overall: low risk. Harbourne, 2001. Randomization process: some concerns. Deviations from the intended interventions: some concerns. Missing outcome data: low risk. Measurement of the outcome: low risk. Selection of the reported result: high risk. Overall: high risk. Hemayattalab and Rostami, 2010. Randomization process: some concerns. Deviations from the intended interventions: some concerns. Missing outcome data: some concerns. Measurement of the outcome: some concerns. Selection of the reported result: high risk. Overall: high risk. Hemayattalab and alia, 2013. Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: low risk. Selection of the reported result: some concerns. Overall: some concerns. Hemayattalab, two thousand fourteen. Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: low risk. Selection of the reported result: low risk. Overall: some concerns. Hussein and alia, 2019. Randomization process: low risk. Deviations from the intended interventions: some concerns. Missing outcome data: some concerns. Measurement of the outcome: some concerns. Selection of the reported result: high risk. Overall: high risk. Kara and alia, 2020. Randomization process: some concerns. Deviations from the intended interventions: some concerns. Missing outcome data: some concerns. Measurement of the outcome: some concerns. Selection of the reported result: some concerns. Overall: some concerns. Talbot and Junkala, 1981 Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: some concerns. Selection of the reported result: high risk. Overall: high risk. Thorpe and Valvano, 2002. Randomization process: some concerns. Deviations from the intended interventions: some concerns. Missing outcome data: some concerns. Measurement of the outcome: some concerns. Selection of the reported result: high risk. Overall: high risk. Valvano and Newell, 1995. Randomization process: some concerns. Deviations from the intended interventions: low risk. Missing outcome data: low risk. Measurement of the outcome: high risk. Selection of the reported result: some concerns. Overall: high risk.

Figure 4. Results of risk-of-bias assessment per domain. Green = low risk of bias; red = high risk of bias; yellow = some concerns.

Figure showing the percentages of the three verdicts given in each domain, as well as the overall risk of bias. Overall, 8.3% of the studies shows low risk of bias; 41.7% shows some concerns. Fifty percent shows high risk of bias. The domain where relatively many studies, namely 41.7%, showed a high risk of bias, was the domain “selection of the reported result”.

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These are the risk of bias results in percentage for each of the five domains, as well as the overall risk of bias. Randomization process: 16.7% of the studies shows low risk of bias; 83.3% shows some concerns; 0% shows high risk of bias. Deviations from intended interventions: 58.3% of the studies shows low risk of bias; 41.7% shows some concerns; 0% shows high risk of bias. Missing outcome data: 66.7% of the studies shows low risk of bias; 33.3% shows some concerns; 0% shows high risk of bias. Measurement of the outcome: 41.7% of the studies shows low risk of bias; 50% shows some concerns; 80.3% shows high risk of bias. Selection of the reported result: 25% of the studies shows low risk of bias; 33.3% shows some concerns; 41.7% shows high risk of bias. Overall: 8.3% of the studies shows low risk of bias;41.7% shows some concerns; 50% shows high risk of bias.

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