Intermittent feedback for both groups was provided according to a faded feedback protocol in which the feedback was provided for 80% of the trials in training sessions 1 to 4, 60% of the trials in training sessions 5 to 8, and 40% of the trials in training sessions 8 to 12. Feedback was structured on the basis of the guidance hypothesis,26 wherein the beneficial effects of augmented feedback for reducing error can ultimately impede learning if the learner comes to depend on the feedback. This protocol of fading the frequency of feedback was developed on the basis of previous investigations that demonstrated that progressive fading of feedback over every one-third trials (over the course of training) was effective in promoting motor learning.27,28
Participants in both groups performed 150 to 200 movements, using the paretic arm in each training session. Some participants were able to achieve only 150 movements at the start of training but eventually worked up to more repetitions. Other participants were able to achieve close to 200 movements at the start of training and therefore required more complex tasks to work at the highest level of their ability during the 1-hour training session.
Participants were instructed to move at their preferred speed. Preferred speed was selected because, during pretraining trials using the pressure sensor device, errors rates were excessive when participants were required to adhere to an imposed speed criterion. Furthermore, while factors such as intensity of practice, motivation, repetition, and variability have been found to influence poststroke motor rehabilitation in TRT investigations,29 speed has not been shown to be a critical factor. However, once training progressed and participants began to find the tasks easier, they were encouraged to increase performance speed. If a participant completed the required training tasks in less than 45 minutes, then subsequent sessions employed more complex reaching tasks.
Participants were seated in a standard chair with no armrests. The chair was placed at a table with a large workspace and positioned so that there was a clearance of approximately 10 cm (4 inches) between the participant's body and the edge of the table. Objects were placed in different locations on the tabletop so that reaches of various directions and amplitudes were required to contact or grasp them. Participants were able to move the arm anywhere objects were placed, as all objects were placed within the arm's length.
Training activities progressed from reaching to contact objects, then reaching and grasping, and eventually transporting the objects. Common objects were used (eg, cups, mugs, writing, and eating utensils) and the objects varied in size, shape, and weight. Training also included unimanual activities such as sliding the arm across the tabletop with objects in the hand or tossing balls into boxes placed throughout the workspace. Bimanual activities included using 1 hand to pour water or open a container, while the other hand stabilized the object, moving objects in/out of containers, bimanual cutting activities, and folding activities. Training activities were adapted from literature related to reaching to grasp theories.30
A 2 × 2 (Group × Time) analysis of variance with repeated measures on the factor Time was used to determine whether there were significant between-groups differences in the pretest/posttest change in outcome measures.31 Significant differences were further tested using post hoc comparisons between groups, according to Tukey's HSD (honestly significant difference) Test.32 Significance for all tests was set at P < 0.05. Levene's Test of Equality of Variance was used to confirm whether the data were normally distributed.
Age and pretest scores on outcome measures were not significantly different between groups. Mean age for the Sensor group was 62.9 ± 6.5 years and for the Stabilizer group was 63 ± 9.2 years. There were no differences in pretest scores between groups on the RPS-near (P = 0.53), RPS-far (P = 0.88), FMA (P = 0.24), WMFT (P = 0.56), shoulder flexion (P = 0.71), or elbow extension (P = 0.24).
For the RPS-near target, there was a significant main effect of Time (P < 0.01). There was also a significant Time × Group interaction for this measure (P < 0.04; see Figure 3). Post hoc analysis indicated that these differences were explained by the significantly greater improvement for the Sensor group compared to that for the Stabilizer group. For the RPS-far target, there was a significant main effect (P < 0.01) of Time, with no significant interaction effect.
For the FMA scores and the WMFT scores (P < 0.04), there was a significant main effect of Time (P < 0.02). For shoulder flexion AROM, there was a trend toward a main effect for improvement (P = 0.059). Measures of elbow extension (P = 0.1), grip strength (P = 0.69), and MAL (amount of use scale; P = 0.78) yielded no significant changes. All data are shown in Table 2.
Results indicated that faded sensory feedback in the form of both extrinsic auditory feedback (Sensor group) and intrinsic tactile feedback (Stabilizer group) yielded changes in impairment and activity measures. Improvements were observed in reaching (both RPS-near and -far), shoulder AROM, FMA, and WMFT for these individuals with moderate or severe arm impairments due to chronic stroke. However, reaching in the immediate workspace (RPS-near) improved more with auditory feedback.
Although previous work has demonstrated positive effects of using trunk restraint to promote improved arm use,9,15 there has been minimal information on the value of using auditory feedback from a pressure sensor device.17 The improvements made in the Sensor group further support the use of an external device to increase awareness of sensory events that accompany movements while learning a motor task. One systematic review evaluating the use of augmented feedback during rehabilitation (primarily in individuals with stroke) concluded that there was no firm evidence supporting its effectiveness for improving motor function of the upper extremity.33 The main reason for this finding was that the longer-term effects of auditory feedback were often not investigated in the studies available for review. In a more recent review of the effect of extrinsic feedback on motor learning in the upper limb poststroke, auditory feedback was found to improve movement quality immediately following training.18
The RPS measures the timing, smoothness, and directness of reaching movements.21 The finding that reaching performance within the participant's immediate workspace significantly improved without a trunk restraint (an approach that has dominated the literature in this area) supports the value of utilizing some form of auditory feedback for reaching to grasp activities.9,15 It is possible that reliance on an external trunk stabilizer to place pressure on the anterior shoulder during training may limit the ultimate goal of this training, which is to reach out and away from the body with the impaired arm, thereby allowing for more use and function during everyday tasks. With the use of auditory feedback from a pressure sensor, a physical restraint does not prevent movement from occurring; rather, the individual makes a cognitive decision to control the trunk in response to an auditory feedback signal.
In explaining movement recovery, it is important to know whether gains in movement (both performance and outcome) are due to recovery or compensation.22 Recovery is the reappearance of premorbid movement patterns while compensation is the appearance of alternative movement patterns.6,22 The population studied in the present investigation, classified as having moderate or severe impairment, has typically gained functional improvement by compensatory methods, such as greater trunk displacement/rotation, scapular elevation, shoulder abduction, and internal rotation.34,35 Physically restricting trunk movements to gain upper limb movement has been effective in improving motor patterns and limiting compensatory strategies in less-impaired individuals.3,15 The outcomes of the present study indicate that individuals poststroke with moderate or severe arm impairments have the potential to exhibit recovery with training that incorporates auditory feedback. The similar positive results for the majority of outcome measures in this investigation (for both extrinsic auditory feedback and intrinsic tactile feedback) suggest that the common component of this training, TRT with faded sensory feedback, is the primary factor underlying improvements. These findings and our prior findings3,15 indicate that TRT is associated with improvements regardless of whether training was carried out with or without trunk-restraint. Recent reviews of the evidence for stroke rehabilitation and recovery demonstrate strong support for TRT focusing on repetitive practice of meaningful tasks of progressively increasing difficulty.36 When the trunk is free to move during reaching, individuals poststroke with more severe impairments of arm function use trunk motion to compensate for inadequate control of the upper limb.3,9,13,34 This suggests that if the individual is not trained to control the trunk, those with moderate or severe impairments of arm function will make more compensatory movements during reaching activity. Current clinical opinion dictates that compensatory strategies should not be encouraged as these movements are associated with problems such as pain, discomfort, and joint contractures.4,37
The fact that the investigator who performed the data collection and analysis was not blinded to the participant treatment group is a limitation of this investigation. In addition, the sample size of this study was small, which may have masked significant group effects for measures such as the WMFT and the MAL, that have great amounts of variability. Prior studies have shown training-related changes in MAL scores in individuals with more severe impairment than participants in the current study.39,39 Furthermore, a qualitative component (beyond the MAL) asking participants about their experiences and perceptions about the program and its results may have captured significant changes in participation. It is the opinion of the author that the Motor Assessment Scale has floor/ceiling effect, limitations and thus was used in this investigation only as an exclusion criteria.
Studies with additional analyses and long-term follow-up are needed. To answer questions about the value of auditory pressure feedback, information about long-term retention of improvements in arm function, movement quality, and decreases in compensatory trunk movement are necessary. Thus, more sophisticated movement analysis and extended follow-up of these participants are important. Measures to identify neuroplastic changes related to this type of training, such as a functional magnetic resonance image, would further support the value of this approach. Future investigations should address these issues.
In individuals with moderate or severe arm impairment poststroke, TRT that incorporated auditory sensory feedback about trunk movement was associated with improved reaching and functional use of the hemiparetic arm. While most results were comparable to those obtained with training that incorporated trunk stabilization, improvements in reaching in the immediate workspace were greater with the auditory feedback. Extrinsic feedback training should be considered for individuals poststroke. Based on these pilot findings, future randomized controlled investigations would be indicated to further evaluate training protocols that utilize fading of feedback for the stroke population.
We thank the following USP graduate students who assisted in the training of the participants: Kate Bartnik, Ravi Buddharaju, Pat Hennessy, Julie Kametz, Stacy Prokopchuk, and Kim Wallace.
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Keywords:© 2010 Neurology Section, APTA
hemiplegia; reaching; recovery of function; rehabilitation