David J. Reinkensmeyer, Member, IEEE and Sarah J. Housman

Transcription

1 If I can t do it once, why do it a hundred times? : Connecting volition to movement success in a virtual environment motivates people to exercise the arm after stroke David J. Reinkensmeyer, Member, IEEE and Sarah J. Housman Abstract We are attempting to develop therapeutic technology that individuals with substantial arm weakness and minimal hand function after stroke can use to improve their movement ability without the continuous presence of a rehabilitation therapist. We have developed a device called Therapy WREX (T-WREX) that is comprised of four main features: 1) a passive, gravity-balancing arm support (based on WREX Wilmington Robotic Exoskeleton) that allows a wide range of arm motion 2) a grip sensor that detects even trace amounts of grasp 3) virtual reality exercises that simulate activities of daily living, and 4) software that provides feedback about task performance. Initial clinical testing indicates that chronic stroke patients can significantly improve their movement ability with T-WREX. We have also found that patients strongly prefer using T-WREX for therapy compared to conventional, self-directed, tabletop exercises. This paper reports the results of a follow-up survey conducted with 11 subjects to gain further understanding about the basis for this preference. The results suggest that subjects prefer T-WREX because it is more interesting, and because it allows them to be more successful with their movement attempts. Further, each of the four features of TWREX had significant value to the subjects, suggesting that their combination is synergistic. A I. INTRODUCTION key issue for individuals with severe weakness after stroke is the negative impact the weight of the limb has on upper extremity (UE) movement. Those with significant weakness cannot generate enough force to overcome gravity, and, as a result, become frustrated and stop practicing movement. The clinical standard for encouraging self-directed exercise in this situation is to use a table-top to support the arm against gravity and a towel to remove the friction between the arm and the table during movement attempts. This approach is simple, inexpensive, and widely used. Yet, it is boring, lacks objective feedback, and has questionable compliance. Clinicians and engineers have also developed simple technology for relieving the weight of the arm such as mobile arm supports, arm skateboards, and overhead slings. Such devices are present in many clinics, but are used inconsistently because they are not engaging and can be difficult to set up. At the high end of complexity are robotic devices, such as MIT-MANUS [2], MIME [3], the ARM Guide [6], Gentle-S [4], ARMIn [8], NeReBot [9] and VRROOM [10], which not only support the arm, but also provide robotic guidance. These devices are powerful tools for studying rehabilitation therapy; however, whether their therapeutic benefit is proportional to their cost remains to be demonstrated. What has been demonstrated is the importance of repetitive practice of movement attempts, with or without robotic guidance present [11, 12]. We have developed an arm therapy device that attempts to bridge the gap between boring table top exercise and expensive robotic therapy. Therapy WREX (T-WREX) [7, 13] uses a passive, gravity-balancing orthosis (based on WREX Wilmington Robotic Exoskeleton, developed by Rahman et al. [14]), a hand grip sensor, and virtual reality exercises to allow people with severe weakness to practice simulated functional activities (Fig. 1A). T-WREX is nonrobotic, but allows severely weakened patients to move by providing gradable assistance against gravity with elastic bands and sensing even small changes in grasp force with the grip sensor. It avoids the complexity of 3D virtual reality by focusing on the practice of simulated functional activities with a well-designed 2D display, for which movement is displayed only for a selected plane of actual motion (Fig. 1B). The exercises are easy to learn and approximate the movements needed for ADL. Hocoma A.G. A B Manuscript received February 9, This work was supported in part by the U. S. Department of Education National Institute on Disability and Rehabilitation Research (NIDRR) under Grant H133E020732, as part of the Machines Assisting Recovery from Stroke (MARS) Rehabilitation Engineering Research Center (RERC) on Rehabilitation Robotics and Telemanipulation, and by NIH N01-HD from NCMRR and NIBIB. S. J. Housman is with the Rehabilitation Institute of Chicago Sensory Motor Performance Program, Chicago, IL USA (phone: ; fax: ; shousman@ric.org). D. J. Reinkensmeyer is with the University of California at Irvine Department of Mechanical & Aerospace Engineering, Irvine CA USA. ( dreinken@uci.edu). Fig. 1: A) T-WREX relieves the weight of the arm and measures arm and hand movement. B) Example of a T-WREX game: user reaches for objects on the shelves, squeezes to grip the object, moves to the shopping cart, and releases to drop the object. Other games simulate driving, cooking, cleaning, self-care, and sports.

2 plans to begin selling a device called ARMEO in summer 2007 based on the T-WREX concept, including VR software. Initial clinical testing with T-WREX has demonstrated that it can improve UE movement ability following chronic stroke [7, 13] (Fig. 2A). For example, in an ongoing randomized, controlled study we are comparing motor training with T-WREX to a matched amount of conventional, self-directed tabletop exercises following chronic stroke. Briefly, the preliminary results from this study indicate that repetitive motor training with T-WREX can reduce motor impairment for chronic stroke survivors with moderate to severe upper extremity hemiparesis [7]. Individuals in the T-WREX (n = 13) and control groups (n = 12) demonstrated significant improvements in arm movement ability according to the Fugl-Meyer scale (mean±sd: 3.7±2.7 and 2.7±2.7) points on average, respectively, Fig. 2A). Subjects in both groups reported nearly significant gains on a functional scale that grades quality and amount of affected arm use in the home setting (Fig. 2B). There were no significant differences between groups with the current sample size. Both groups required about 4 minutes of direct contact with the supervising therapist for each hour therapy (primarily to set-up and initiate therapy), as measured with a stopwatch. After they completed the two month training program, subjects in both training groups were given an opportunity to try the other training technique for one training session. Subjects completed a survey rating their subjective opinions on each therapy type after the cross-over training session. Subjects in both training groups strongly preferred the use of T-WREX for therapy (Fig. 2C). 100% of subjects assigned to T-WREX treatment reported a preference for this type of training and would recommend T-WREX over conventional training. In addition, 100% of these subjects found the therapy less boring and easier to track their progress than conventional tabletop exercises. Control group participants also demonstrated strong preferences for T-WREX therapy, with 89% of controls finding the one-session sample of T- WREX exercises that they experienced less boring and more beneficial. An average of 73% of subjects from both groups also considered T-WREX more functional, and 80% reported an increased likelihood to complete this therapy in the home over conventional tabletop exercises. In the original survey, we did not ask the subjects why they preferred T-WREX to conventional tabletop therapy. We report in this paper the results of a follow-up survey conducted with a subset of 11 subjects to try to understand the basis for this strong preference. We were also curious if any one of the four key components of T-WREX (arm support, hand grip, computer games, feedback) accounted for this preference. Finally, we asked subjects how important new features for T-WREX would be, given several proposed options. II. METHODOLOGY We conducted the survey by telephone with 11 individuals who had participated in the randomized controlled test of T-WREX at the Rehabilitation Institute of Chicago. Five respondents had been enrolled in the group that received therapy with T-WREX, and six in the group that received the control therapy (tabletop exercise). The subjects had also participated in one cross-over training session with the alternate exercise program (i.e. the control therapy for the T-WREX group, or T-WREX therapy for the control group) following completion of their original 8-week therapy program. The average time post-stroke was 8 years, and the average Fugl-Meyer arm impairment score was 20 out of 66. The survey contained three sections. The first section was an open-ended narrative in which we asked subjects to tell us why they preferred T-WREX. The second section Fig. 2: A. Improvements in upper extremity (UE) movement ability were significant (p < 0.001), as measured with the UE Fugl-Meyer (FM) scale [1] following chronic stroke after two months of T-WREX therapy (n = 13) and conventional table top exercise (n = 12), as measured in the study in the current MARS RERC. For comparison, improvements in UE FM score for chronic stroke patients with the arm-therapy robotic devices MIT-Manus[2], MIME[3], and Gentle-S[4] with similar durations of therapy are shown. B. Increased amount of functional arm use, measured by the MAL Amount of Use subscale [5] ( Quality of Movement subscale not shown) after two months of T-WREX therapy is small but nearly significant, and larger than conventional table-top therapy. The MAL scale ranges from 0 (no use) to 5 (normal use). C. Percentage of subjects preferring T-WREX therapy compared to conventional, self-directed table-top exercise. Subjects in both groups were given a chance to try each therapy, and then select which one they preferred in 10 categories, of which 4 are summarized here. Data is summarized from [7].

3 required the subjects to determine the relative importance of each of the four T-WREX features (arm support, hand grip, computer games, feedback). To gauge importance, subjects were asked how much money they would spend on each feature if they were given $100 total to buy all of the features. Subjects were instructed to spend more money on items they considered more important and less money on features less important to them. In the third section, subjects were asked how they would spend $100 on several new features that we are considering developing for T-WREX. The exact survey questions are given in Tables 1 and 2. III. RESULTS A. Why did subjects prefer T-WREX training to tabletop exercises? When we asked why they preferred T-WREX, some subjects emphasized that T-WREX was more interesting: T-WREX wasn't so boring and it was more interesting (a 64- T-WREX was more interesting. The table exercises were kind of a drag. T-WREX is more interactive, and you are doing it all with your bad arm and not assisting at all with your good arm. (a 53-yearold) I had done most of the tabletop exercises as an inpatient and outpatient, and T-WREX was new; I hadn't tried it before. (a 28- Things like SAEBO and tabletop exercises are boring, repetitive (picking up balls with SAEBO); the T-WREX is more interesting. T-WREX is more challenging than tabletop and SAEBO. (a 52- Others subjects also spoke of the challenge and feedback that T-WREX provided: "T-WREX gives you more to do, something to shoot for. Table exercises are the same thing every day, and you make up your own criteria (for success/progress). T-WREX challenges you." (a 58- T-WREX gives you real-time response to your activity. You could actually see what you were doing; You could get better with the T-WREX motion." (a 61- Other subjects spoke of moving the arm more successfully during T-WREX exercises: The T-WREX moves your arm much better. I move my arm much better during the game than just on the tabletop. (a 70- "T-WREX was easier to understand and to move" (a 60- T-WREX was easier and it seemed like I was accomplishing more; with the tabletop I didn't feel like I was accomplishing anything. (a 62- The T-WREX supported my arm real good. With the table exercises, I just couldn't do some of the exercises, so if you can't do it once, why do it a hundred times? With T-WREX, I could actually do it. (a 50- B. What features of T-WREX did the subjects value the most? In the second part of the survey, we asked subjects how much money they would spend on the four key features of T-WREX (arm support, hand grip, computer games, feedback) if they were given $100 to buy different features. Table 1 shows the results. TABLE I SUMMARY OF RESPONSE TO SECOND PART OF SURVEY IN WHICH WE ASKED SUBJECTS WHAT FEATURES OF T-WREX WERE WORTH THE MOST TO THEM If you were given $100 to buy different features of Mean ± SD the T-WREX, how much money would you spend on each feature? 1) The arm support that made your arm feel 38 ± 21 weightless during training (If you don t buy this feature, you would practice with your arm on a tabletop or without any support) 2) The computer games (If you don t buy this feature, 21 ± 12 you would practice moving your arm without playing games on the computer) 3) The grip sensor that allowed you to use your hand for grabbing and releasing items in the games (If you don t buy this feature, you would not be able 25 ± 17 to practice grabbing and releasing with your hand) 4) The program that measured your performance and gave you feedback at the end of each game (If you don t buy this feature, you would not get information from the machine about your improvements in arm motion) 16 ± 11 Subjects assigned the most money to the arm support, followed by the grip sensor and then the computer games. The program which measured performance and provided feedback received the least money, significantly less than the arm support (paired t-test, p < 0.02) and marginally significantly less than the grip sensor (p = 0.08). C. What new features did the subjects want for T-WREX? In the third part of the survey, we asked subjects how they would spend $100 on several new features that are proposed as enhancements for T-WREX. The results are shown in Table 2. Subjects preferred a device that helps move their hand and wrist (a feature that scored significantly higher than any other feature, paired t-tests, p < 0.05), followed by robotic assistance for the arm, and games that adapt to the patient s abilities. The lowest scoring item was to add more computer games. T-WREX currently has 10 games (Selffeeding, Grocery shopping, Cleaning a stovetop, Washing a window, Driving, Playing basketball, Squeezing mustard on a hot dog, Picking up and cracking an egg over a pan, Washing the opposite arm, and Reaching for orbiting planets). As a follow-up question, we asked all 11 subjects if they would prefer arcade-style games or games that mimic daily

4 activities if we were to develop new games. Subjects preferred games that mimicked daily activities, although the preference was not strong nor statistically significant (Table 2, bottom). In addition, this question was likely strongly sensitive to the specific games that were listed as examples. IV. DISCUSSION AND CONCLUSION What was it about training with T-WREX that made subjects almost uniformly prefer it to conventional, table-top exercise? None of the subjects stated that they thought T- WREX had greater therapeutic efficacy (and preliminary clinical outcomes support this concept, although the study is ongoing and all measures have not yet been analyzed). Rather, their answers focused on the interest that T-WREX provided, and the improved movement ability that they had when they used it. The references to improved interest appear to speak to the interactive nature of the computer games, in which subjects are rewarded for specific arm movements (lifting the arm up and away from the body, for example) by virtual task success (observing a basketball moving into a basket and hearing simulated cheering from the crowd). In addition, subjects are able to track their progress and success by competing against their own daily and all-time high scores. We hypothesize that T-WREX exercises were perceived as more interesting because the tabletop exercises do not provide a comparably engaging environment with objective markers of success. In addition, subjects stated that T-WREX exercises were less frustrating and allowed greater movement success. Subjects were able to move the arm through a greater range of motion with T-WREX, and could use the hand to interact with virtual environments, even though the hand was very weak and essentially non-functional during daily activities. We propose therefore that T-WREX was attractive because it enhanced the functional causality of movement. By functional causality of movement we mean the subject s ability to volitionally effect a movement that caused something meaningful to happen in a simulated environment. Enabling functional causality is important for this population of stroke survivors, because these subjects have moderate to severe arm and hand weakness, which significantly limits their ability to use the affected arm successfully during activities of daily living. In fact, prior to treatment, all subjects rated the average amount of affected arm use as 0.46 on the 5-point Motor Activity Log rating scale, with a score of 0 denoting arm use never or not at all and 5 indicating normal arm use. With this data, it is evident that the subjects rarely used their arms. T- WREX provides a training modality in which these individuals can begin to experience success with movement attempts, and successful completion of the virtual tasks likely reinforces continued, repetitive task practice. An important question in the development of rehabilitation technology is What is the least expensive TABLE II RESPONSES TO THE THIRD PART OF THE SURVEY IN WHICH WE ASKED SUBJECTS WHAT NEW FEATURES THEY WOULD PAY FOR We are developing a new T-WREX. Pretend you Mean ± SD were given $100 to make the new T-WREX better than the version you tried. How much money would you spend on each new feature? 1) Making the arm support robotic (So that a motor can help you move your arm through a wider range of motion) 2) Adding a device that helps you move your wrist and hand (This would help turn your palm up, move your wrist backwards, open your hand, etc. while playing the games) 3) Adding more computer games (To increase the variety) 4) Improving the current system which provides feedback about your arm movement (So that you are given more accurate information about improvements in your movement) 5) Games which adapt to your abilities and provide the right amount of challenge (This program would monitor your movement and make the games easier or more difficult based on your current abilities) You identified more computer games as one feature you would spend money on. If you were given $100 to spend on computer games alone, how much money would you spend on these types: 1) Games that mimic daily activities such as eating, cooking, cleaning, and driving 2) Games that simulate arcade-style video games, such as PACMAN, NASCAR, and Star Wars 19 ± ± 26 8 ± 8 11 ± ± 17 Mean ± SD 59 ± ± 22 way to facilitate effective therapy? If we accept the hypothesis that functional causality is a key motivator for UE therapy, then what is the simplest, least expensive technology to provide it? Robotic devices can provide it, but simpler passive devices like T-WREX can as well. Are there possibilities even simpler than T-WREX that could provide it? A related question is What is the minimum amount of functional causality required to motivate subjects and promote recovery of movement? and Could this causality be provided with a visual display and sensors that sense small movements, or is a mechanically enhanced range of limb movement actually required for therapeutic effect? We are unsure of the answers to these questions, but in order to probe the subject s opinion on these questions with respect to T-WREX, we asked how they would spend money to buy existing T-WREX features. We expected that one of the features we thought the grip sensor would be relatively unimportant. The arm support was the most important feature, followed by, to our surprise, the grip sensor, and then close behind and with similar value the games and feedback. Thus, all four elements of T-WREX were important to the subjects, and doing without any one of the elements (but particularly the arm support) would seemingly be undesirable. This suggests that coordinated use of arm and hand, the assistance to movement provided by arm support, the engaging virtual environment, and the

5 feedback work synergistically to provide functional causality and motivate subjects. When asked what features they would invest in for future versions of T-WREX, the subjects strongly emphasized better hand/wrist assistance, suggesting that they were frustrated by their inability to use their hands, which were very impaired for all subjects. Surprisingly, adding more computer games and improving the feedback were the least important. This suggests that a library of 10 games that have simple 2D graphics and simulate activities of daily living is sufficient to hold subjects attention, and that simple feedback suffices for motivation. The question remains, however, whether the subjects experienced the problem of unconceived alternatives [15]. That is, it is likely that games and feedback schemes exist, currently unimagined by the subjects, which would prove more desirable if the subjects experienced them. Providing more assistance through robotic actuation for the arm and the creation of sensitive games which continuously adapt to the patient s abilities were also moderately appealing to the subjects. If the dollar values of these two features are combined into a single score that corresponds to a feature such as technology that helps me to achieve tasks, then the combined score rivals that of the score for wrist/hand assistance. This result therefore suggests that providing technology that provides an appropriate amount of challenge and success is important. All of these results should be considered in light of the following study limitations: the study sample size was small (n = 11), the questions were strongly related to a specific device and therefore may not generalize, and a particular survey format (the buy features on a budget format) was used to assess features. In his recent book, The Culture Code [16], marketing expert Clotaire Rapaille details the results of discovery sessions that he has held over the last 30 years with thousands of consumers in different cultures to determine the underlying, cultural code for different products or concepts. The code refers to the stereotypical, primitive, emotive association or impression the consumers have in response to a product or concept. He claims that the code for health in the U.S. is movement. People feel relatively healthy if they can move. This is consistent with the idea that it is the increased ability to move conferred by T-WREX arm support that makes it relatively attractive to people with severe weakness after stroke. In addition, T- WREX rewards movement with successful completion of simple virtual reality games that the subjects find interesting, i.e. improved functional causality. 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