Applying Space Technology to Enhance Control of an Artificial Arm

At the present time, myoelectric prostheses perform only one function of the hand: open and close with the thumb, index and middle finger coming together to grasp various shaped objects. To better understand the limitations of the current single-function prostheses and the needs of the individuals who use them, The Institute for Rehabilitation and Research (TIRR), sponsored by the National Institutes of Health (August 1992 - November 1994), surveyed approximately 2500 individuals with upper limb loss. When asked to identify specific features of their current electric prosthesis that needed improvement, the survey respondents overwhelmingly identified the lack of wrist and finger movement as well as poor control capability. Simply building a mechanism with individual finger and wrist motion is not enough. Individuals with upper limb loss tend to reject prostheses that require continuous visual monitoring and concentration to control. Robotics researchers at NASA's Johnson Space Center (JSC) and Rice University have made substantial progress in myoelectric teleoperation. A myoelectric teleoperation system translates signals generated by an able-bodied robot operator's muscles during hand motions into commands that drive a robot's hand through identical motions. Farry's early work in myoelectric teleoperation used variations over time in the myoelectric spectrum as inputs to neural networks to discriminate grasp types and thumb motions. The resulting schemes yielded up to 93% correct classification on thumb motions. More recently, Fernandez achieved 100% correct non-realtime classification of thumb abduction, extension, and flexion on the same myoelectric data. Fernandez used genetic programming to develop functions that discriminate between thumb motions using myoelectric signal parameters. Genetic programming (GP) is an evolutionary programming method where the computer can modify the discriminating functions' form to improve its performance, not just adjust numerical coefficients or weights. Although the function development may require much computational time and many training cases, the resulting discrimination functions can run in realtime on modest computers. These results suggest that myoelectric signals might be a feasible teleoperation medium, allowing an operator to use his or her own hand and arm as a master to intuitively control an anthropomorphic robot in a remote location such as outer space

The differential influence of pain and fatigue on physical performance and health status in ambulatory patients with human immunodeficiency virus

Objectives: The purposes of this study were to: 1) characterize physical performance in individuals with human immunodeficiency virus; and 2) examine group differences by pain and fatigue on a multivariate profile of disease, physical, and psychologic symptoms.Methods: One hundred outpatients, 78 men and 22 women (mean age 40.70 +/- 7.49 years) participated. Patients completed a battery of physical performance tests in which the time taken or the distance reached or walked was measured. Self-report questionnaires included measures of pain (0-10 numerical rating scale), fatigue (Brief Fatigue Inventory), and perceived health status (Medical Outcomes Survey-HIV scale).Results: Physical performance was compromised in a task specific manner. Patients took twice as long as healthy individuals on a belt-tie and 4 times as long on a sit-to-stand task and in 6 minutes walked 75% of the distance covered by healthy individuals. Fifty percent of patients (n = 50) had pain at the time of testing (mean 6.3 +/- 2.4), and 98% had fatigue (mean 5.4 +/- 2.3). Multivariate analysis of variance showed pain had a greater influence on performance than fatigue. Pain, distance walked in 6 minutes, and unloaded forward reach accounted for 26% of the variability in quality of life (r = 0.51, P <= 0.0001).Discussion: Pain has a substantial impact on physical performance and quality of life among ambulatory human immunodeficiency virus patients. Fatigue also impacts physical performance. Compromised ability to perform certain physical tasks affects quality of life. Further investigation of the roles of these relevant variables should be investigated in path analyses

Generalized Anxiety Disorder in Hispanics: Symptom Characteristics and Prediction of Severity

Literature suggests that an increasing number of Hispanic people suffer with GAD, and possible associated problems include high costs for treatment and elevated risk of severe impairment. The current study examined components of anxiety, as measured by currently available assessment instruments in both English and Spanish languages, among bilingual Hispanic individuals with GAD. Participants completed all instruments in both languages. Relations between these self-report measures and clinician-rated GAD severity were also studied. In factor analyses, the Spanish measures yielded two factors, the first of which included all instruments assessing physiological components of anxiety and one content specific measure of worry. The second factor included one worry scale and one trait anxiety scale. The English measures yielded a single factor solution. Regression analyses revealed that for the English measures, the BAI and PSWQ were statistically significant predictors of GAD severity. For the Spanish measures, the BAI was the only statistically significant predictor

Physical performance tasks: what are the underlying constructs?

OBJECTIVES: To investigate the structural validity of a battery of physical performance tasks and to investigate the construct validity of the resulting factors.DESIGN: A measurement study.SETTING: A large, private orthopedic clinic and a physical therapy clinic in an urban area. PARTICIPANTS: One hundred three consecutive adult patients with low back pain who were referred for physical therapy assessment.INTERVENTIONS: Not applicable.MAIN OUTCOME MEASURES: The physical performance battery was composed of the 50-foot speed walk, 5-minute walk, repeated trunk flexion, sit to stand, loaded reach, rollover tasks, and Sorensen upper-body lift. Participants also completed 5 self-report measures.RESULTS: Two correlated (.74) factors, speed and coordination and endurance and strength, were derived from the physical performance tasks. The Sorenson upper-body lift task was the only indicator that was not useful in defining the factors. Both factors had statistically significant correlations with measures of physical disability, lack of self-efficacy, and negative affect. Both factors had a trivial correlation with a numeric rating of pain intensity.CONCLUSIONS: There is support for 2 meaningful empiric groupings (ie, the derived factors) of the performance tasks. Pain intensity had a trivial overlap with speed-coordination and endurance-strength factors

Functional self-efficacy, perceived gait ability and perceived exertion in walking performance of individuals with low back pain

The purpose of this study was to examine psychological and perceptual factors that influence walking in individuals with low back pain (LBP). In Study 1 59 subjects with LBP recruited from an orthopedic surgeon participated. Perceived gait ability was measured with the Distorted Ambulation subscale of Pain Behavior Checklist (DAS-PBCL). The psychological factor of functional self-efficacy (FSE) was assessed on the FSE scale. These scales were completed before performing a 50-foot speed walk (50 FT WALK) and a 5-minute distance walk (5 MIN WALK) tests. DAS-PBCL had stronger correlations with walking performance (r = 0.11 to 0.58) than FSE (r = 0.03 to 0.49). DAS-PBCL had a stronger relationship with 50 FT WALK ( r = 0.18 to 0.58) than 5 MIN WALK (r = 0.11 to 0.50). In Study 2 48 healthy pain-free subjects and an independent sample of 40 subjects with LBP referred from an orthopedic surgeon participated. They completed the 5 MIN WALK followed by the modified Borg's rating of perceived exertion scale (CR10). Subjects with LBP walked a significantly shorter distance (t = 4.69, p<.005) but perceived a similar amount of exertion (Mann-Whitney U = 861.5, p = .40) compared with those without LBP. Perceived gait ability appears to account for more variability in walking performance than functional self-efficacy of walking in individuals with LBP. Perceived gait ability, in particular, accounted for more variance in walking speed than in walking endurance. Individuals with LBP also experience more exertion during walking than those without LBP. These results suggest that clinicians may need to consider patients' perceptions of gait ability and exertion when assessing walking performance in patients with LBP

Self-reports and clinician-measured physical function among patients with low back pain: a comparison

OBJECTIVE: To determine the relationships among self-reported activity limitation and clinician-measured functional performance tests.DESIGN: Case series survey.SETTING: A referral-based orthopedic spine clinic in Houston, TX.PATIENTS: Eighty-three patients (48 women, 35 men) with low back pain (LBP). INTERVENTIONS: The Roland-Morris Disability Questionnaire (RMDQ) and a physical performance test (PPT) battery.MAIN OUTCOME MEASURES: Self-reported activity limitation (eg, walking, bending, getting out of chair, putting on sock, doing heavy jobs) was assessed by the RMDQ. Clinician-measured functional performance was assessed with the PPT, a battery comprised 6 tests: lumbar flexion range of motion, a 50-foot walk at fastest speed, a 5-minute walk, 5 repetitions of sit-to-stand, 10 repetitions of trunk flexion, and loaded reach task (patients reached forward while holding a weight weighing 5% of their body weight).RESULTS: Pearson's product-moment correlations between total RMDQ score and each of the performance tests ranged from.29 to.41. Point biserial correlations between individual RMDQ items and their corresponding performance tests were slightly lower, ranging from.20 to.33.CONCLUSION: There were moderate correlations between self-reported activity limitation and corresponding clinician-measured performance tests. The unique perspective each method provides appears to be useful for a comprehensive understanding of physical function in patients with LBP

Applying Genetic Programming To Control Of An Artificial Arm

Robotics researchers at NASA's Johnson Space Center (JSC) and Rice University have made substantial progress in myoelectric teleoperation. A myoelectric teleoperation system translates signals generated by an able-bodied robot operator's muscles during hand motions into commands that drive a robot's hand through identical motions Farry's early work in myoelectric teleoperation used variations over time in the myoelectric spectrum as inputs to neural networks to discriminate grasp types and thumb motions; schemes yielded up to 93% correct classification on thumb motions. More recently, Fernandez achieved 100% correct non-realtime classification of thumb abduction, extension, and flexion on the same myoelectric data using genetic programming to develop functions that discriminate between thumb motions using myoelectric signal parameters. Genetic programming (GP) is an evolutionary programming method where the computer can modify the discriminating functions' form to improve its performance, not just adjust numerical coefficients or weights. While the function development may require much computational time and many training cases, the resulting discrimination functions can run in realtime on modest computers These results suggest that myoelectric signals might be a feasible teleoperation medium, allowing an operator to use his own hand and arm as a master to intuitively control an anthropomorphic robot in a remote location such as outer space. These early results imply that multifunction myoelectric control based on genetic programming is viable for prosthetics, since teleoperation of a robot by an operator with a complete limb is a limiting or "best-case" scenario for myoelectric control We hypothesize that myoelectric signals of traumatic below-elbow amputees can control several movements of a myoelectric hand with the help of a function or functions developed with genetic programming techniques. We are now testing this hypothesis with the help of NASA/ISC under a NASA/JSC - Texas Medical Center Cooperative Grant. In this study, five adult below-elbow amputees are performing two forearm motions, two wrist motions and two grasp motions using their "phantom" limb and sound limb while we collect myoelectric data from four sites on the residual limb and four sites from the sound limb. We will use a variety of myoelectric signal time and frequency features in a genetic programming analysis to evolve functions that discriminate between signals generated during different muscle contractions

Assessing older adults with generalized anxiety: A replication and extension

Anxiety is a major health problem for older adults. The cornerstone for further work in this area is research that establishes the psychometric utility of standardized measurement strategies to characterize anxiety in older adults. The goals of the current study were to replicate and extend prior research addressing the psychometric properties of five self-report measures of anxiety in a sample of 57 older adults with generalized anxiety disorder (GAD). Data addressed the descriptive characteristics, internal consistency, test-retest reliability, interrelation of subscales, and convergent and divergent validity of the Penn state worry questionnaire (PSWQ), worry scale (WS), Spielberger state-trait anxiety inventory - Form Y (STAI), and two versions of the fear questionnaire (FQ). Descriptive data generally replicated prior findings, with some increased state and trait anxiety in the current sample. Measures were internally consistent, with evidence that a revised version of the FQ that focuses on severity of fear irrespective of associated avoidance demonstrated greater internal consistency than the original version. Measures of content-specific fears and worries (WS, FQ) were stable over time and demonstrated convergent validity. Evidence of convergent validity also was evident for measures of worry and general anxiety (WS, PSWQ, STAI-Trait), but two of these measures (PSWQ, STAI) were not reliable over time. Only the PSWQ showed evidence of divergent validity with respect to self-report measures of depression. Copyright (C) 2001 Elsevier Science Ltd