Identification of lower arm motions using the EMG signals of shoulder muscles.

This investigation explored pattern recognition of EMG signals produced by shoulder area muscles to identify the performance of a select number of lower arm motions. The signals were modelled as fourth-order autoregressive processes with the parameters of the models used to classify the different motions. The recorded EMG signal was bandpass filtered for each individual to improve discrimination between signals. The method was shown to detect and identify EMG signatures produced by at least two, and sometimes three, different arm motions. Discrimination between the signal models for the motions was not affected by load variation or muscle fatigue.

Development and evaluation of an inexpensive sensor system for use in measuring relative finger positions.

An inexpensive sensor was developed using a carbon-based electrically conductive ink. A correlation of the actual flex angle to the measured flex angle of the sensors was obtained by experimentally determining a third-order polynomial that represented the response of the sensor and its hardware system (r = 0.999). The response time, when going from an angle of 0-90 degrees, was extremely good. The sensors exhibited an acceptable dynamic response with an error of less than 5% when flexed repeatedly to an angle of 90 degrees. A second-order polynomial was found to express the resistance as a function of angle (r = 0.999) for all of the sensors tested. Although these sensors are not as precise as the more expensive sensors that are available, it was estimated that the production cost of these sensors was less then US $0.50 a piece. In addition, there are many ways that the sensor production method might be improved to produce more accurate sensors using carbon-based electrically conductive ink. While much additional work is still necessary, the system presented in this paper could be incorporated into a complete device to monitor the rehabilitation of an impaired hand. Unlike other systems that are currently available commercially, this system is inexpensive, easily manufactured, accurate, and could be readily used in a variety of clinical settings.

Modelling the propulsion characteristics of a standard wheelchair.

Recent wheelchair modelling work has focused on the efficiency of the human-racing wheelchair interaction. This paper builds on this work, investigating the development of a model appropriate for those using standard wheelchairs. A wheelchair racing model was initially used as the starting point for the generation of a number of model variations. Force predictions from these variations were compared to load cell data taken from an instrumented wheelchair during propulsion. Additional models where then developed, based on the characteristics of the models that performed best, and used to predict the forces in a second group of subjects. The analysis procedure was originally based on the calculation of a model index as a mathematical estimation of the theoretical closeness each model prediction had with the observed force. Visual comparisons of the force versus time were then incorporated into the procedure for evaluating the physical appearances of the profiles. The combination of the statistical and visual analysis led to selection of the final models for estimating the starting, constant, and stopping phases of wheelchair propulsion. The resulting models provide insight into the effects of a variety of factors on efficiency during propulsion in a standard chair.

Design and evaluation of a sensory feedback system that provides grasping pressure in a myoelectric hand.

Providing accurate sensory information to the individual with a myoelectric limb is of great importance for improving device use in a wide variety of tasks. A number of feedback systems presently being investigated rely on either vibrotactile or electrotactile skin stimulation, which does not provide sensory patterns similar to those in a natural grasping hand. A prototype system was developed to enhance sensory information transfer by using a technique in which the feedback modality (pressure) was the same as the grasping pressure. The present study compared the developed system (pressure) with vibrotactile feedback, vision, and compounds of these three modes. It was found that the pressure-pressure concept reduced grasping pressure replication errors and error variability.

An evaluation device for quantifying joint stiffness in the burned hand.

An electronic device capable of measuring finger joint stiffness has been developed and used to evaluate the effects of dynamic flexion splinting on the recovery of joint motion in patients with burned hands. The device locates an angle of primary (greatest) resistance and the reactive torque at that angle for a selected joint. Using the device, four subjects with stiff hands were measured before and after dynamic splinting treatments. During the 3-day treatment period, there were statistically significant differences in the angle of primary resistance (p less than 0.0001) and reactive torque (p less than 0.001). This initial trial suggests that: (1) finger stiffness can be quantified in terms of reactive torque as well as joint excursion, (2) dynamic rubber-band flexion splinting does alter joint condition and allow increased motion, (3) the amount of initial joint stiffness may be an indicator of treatment outcome, and (4) increasing treatment time may not enhance outcome.

The Effects of Prophylactic Brace Construction Materials on the Reactive Responses of the MCL During Repetitive Impacts.

OBJECTIVE: The purpose of the present study was to investigate the effect of different construction materials on the ability of a prophylactic brace to reduce the stresses sustained by a surrogate medial collateral ligament (MCL) under low-energy repetitive impact conditions. DESIGN AND SETTING: A surrogate leg was fixed at both the hip and foot with the knee in full extension. A prophylactic brace was attached to the surrogate leg and the system struck by an impactor weighing either 6.68 kg or 16.9 kg. SUBJECTS: A single brace design (Am Pro Knee Guard) was used. Three different materials (nylon, aluminum, graphite) were used in constructing the brace uprights. MEASUREMENTS: Tension in the MCL was measured under all conditions of brace material and impactor weight. In addition, the impact impulse response of the system was evaluated. RESULTS: The graphite and aluminum uprights showed significant reductions in both MCL peak tension magnitude (from 12 to 21% improvement) and in the impulse response of the MCL (from 36 to 47% improvement) when compared to the no-brace condition. CONCLUSIONS: The present study indicates that the choice of brace upright material does have a significant effect on the transmission and absorption of low-level repetitive impact forces at the MCL and should be an important consideration in the design of better knee braces.

1998 William J. Stickel Gold Award. The effects of extrinsic muscle forces on the forefoot-to-rearfoot loading relationship in vitro. Tibia and Achilles tendon.

The effects of muscular activity on the distribution of forces under the foot, as well as within the foot, are of great importance for determining the mechanisms of foot pathologies. Limited data exist concerning muscle forces during the gait cycle and the effects of muscle forces conveyed to the ground-reactive forces of the foot. The authors developed a cadaveric loading system to determine the effects of force applied to the Achilles tendon on the forefoot-to-rearfoot loading relationship in eight cadaveric specimens. The study indicated that, during axial loading of the tibia, force was inherently transferred from the rearfoot to the forefoot. However, the observed forefoot-to-rearfoot loading relationship did not match the predicted loading relationship from a rigid-body diagram, as would be observed in a class I lever. The results indicated that, as the force was increased on the Achilles tendon, the change in loads on the forefoot and rearfoot was not linear. Specimens with calcaneal inclination angles greater than 20 degrees demonstrated a more linear increase as compared with those with inclination angles less than 20 degrees.

A systematic approach for introducing innovative product design in courses with engineering and nonengineering students.

In our new global economy, biomedical product development teams need to be even more innovative in an environment constrained by fewer resources with less time from concept to market. Teams are often comprised of individuals spread around the world. To simulate this setting, we revised an existing course to incorporate teams of on-campus and distance students, with each team including both engineers and other specialties. Through interactive lectures and projects, we presented a systematic approach to innovation that should be useful to engineers and non-engineers alike. Students found the course challenging and exciting, displaying an improved ability to work in distributed teams and in developing innovative design solutions.

Development of a learning module using a virtual environment to demonstrate EMG and telerobotic control principles.

A prototype system was developed for use as a teaching tool, allowing students to link EMG monitoring, data smoothing, robotic control, and neural network training within a rapid prototyping virtual environment (VE). The VE software allowed for the rapid development of scenarios and, when linked with EMG data input to a neural network, allowed the user to control an artificial world containing a virtual arm. Student teams then attempted to control the arm in the VE while performing the tasks by use of a neural network system they had specifically developed and trained using their own EMG signals. The results from their system were then translated into a form that enabled the control of a real robot. Students enjoyed the challenge and uniqueness of the module, and were enthusiastic about extending the concept to other areas of interest.

Development of an inexpensive environmental remote control system for a quadriplegic individual.

The purpose of this project was to adapt a Morse code system for use with a personal computer by a high level quadriplegic individual to achieve greater independence around the home. This was done by eliminating the hardwire connection between the wheelchair computer and the personal computer, replacing it with a Morse Code Transmitter (MCT). The MCT performed the same function as the hardwire connection, but served as a remote controlled device. Each device function is controlled by a sip-and-puff switch. When the Morse code function is active (i.e. transmitting the Morse code from the sip-and-puff device to the computer), the wheelchair computer directs its activity to a specific output port within the wheelchair. The computer detects the position of the sip-and-puff switch, activating the desired function. The system has been pilot tested by the subject for a year with a number of advantages and disadvantages found. The subject has been satisfied with the system's reliability, ease of use, and its response time. Increased transmission range was requested, as well as a desire to control more aspects of the environment. Further evaluation and modification of the system is underway; miniaturization and improving the transmission characteristics are priorities.

Supporting undergraduate biomedical entrepreneurship.

As biomedical innovations become more sophisticated and expensive to bring to market, an approach is needed to ensure the survival of the best ideas. The tactic used by Iowa State University to provide entrepreneurship opportunities for undergraduate students in biomedical areas is a model that has proven to be both distinctive and effective. Iowa State supports and fosters undergraduate student entrepreneurship efforts through the Pappajohn Center for Entrepreneurship. This unique partnership encourages ISU faculty, researchers, and students to become involved in the world of entrepreneurship, while allowing Iowa's business communities to gain access to a wide array of available resources, skills, and information from Iowa State University.

Employing 3D virtual reality games to develop ANN for device control: a pilot study.

Non-immersive virtual reality (VR) game scenarios were developed to aid in the collection of EMG parameters from the biceps and triceps while subjects performed a sequenced series of tasks in the virtual environment. For each subject the best ANN configuration (combination of hidden layers and transfer functions) was chosen, with the resulting optimized algorithms used to classify the sequence of contractions and the function type of the subjects while playing new game scenarios. The wide variety of individually configured ANN developed show why it is difficult to train new users of myoelectric devices with a single algorithm. The use of VR-based games shows promise as a training technique for individuals needing to develop control for prosthetic limbs.

Evaluation of a neural net approach for assessing the rehabilitation status of ACL injuries.

The purpose of this investigation was to explore the potential for using a neural network approach in objectively determining the status of ACL (anterior cruciate ligament) rehabilitation. Nine male subjects (three each of non-injured, in-rehab, post-rehab conditions) were matched for size and strength. The testing protocol was established by a physical therapist: each leg was tested at three different speeds on a Cybex machine with electromyography (EMG) and torque data collected concurrently. Neural net training and testing sets were created from the values of peak torque, time to peak torque, EMG mean power frequency, the EMG root mean square (RMS), and a value representing the ACL condition of the tested leg from each of 15 repetitions. The network was then run until reaching a pre-set mean square error value of 0.05 during training. Subsequent test sets were correctly classified with 99% accuracy, demonstrating the potential of the method as a diagnostic aid for detecting and identifying changes over time in the rehabilitation patterns of individuals having ACL injuries.

Development of a braille training device.

This article discusses the development of a system to more easily train both sighted and blind individuals the braille code. The system consists of a braille cell touchpad, a computer, a screen reading program, a voice synthesizer, and software to drive each of these components. The system runs with minimal user input and can be customized to meet user needs.

The use of self organizing maps to evaluate myoelectric signals.

This paper presents a study of the use and accuracy of self-organizing maps (SOM) in classifying myoelectric signal properties. Myoelectric signals were obtained and classified for four upper-limb movements (elbow flexion, elbow extension, wrist pronation and wrist supination) and their force category. This was done for isolated actions as well as for multiple action sequences. The success of the developed SOM ranged from 92%-97% when determining the motion, from 81%-87% in determining the force category, and from 59%-96% in determining sequences of motions. These successes are encouraging for the continued development of this technique for use in controlling real-time complex motions in prosthetic devices.

Gastroesophageal reflux disorders and asthma.

Gastroesophageal reflux (GERD) may trigger asthma. Approximately 77% of asthmatic people experience reflux symptoms, although GERD may be clinically silent in some. Esophagitis is found in 43% of asthmatic people, and 82% have abnormal esophageal acid contact times on esophageal pH testing. Clearly, GERD is prevalent in asthmatic people. Pathophysiologic mechanisms of acid-induced bronchoconstriction include a vagally mediated reflex and microaspiration. Whether these airway responses are clinically significant is the subject of some debate. Interestingly, peak expiratory flow rates and specific airway resistance alterations persist despite esophageal acid clearance. Preliminary evidence shows that substance P, an inflammatory mediator that causes airway edema, is released with esophageal acid. Although therapeutic studies are limited by their small population sizes and study design, up to 70% of asthmatic people have asthma improvement with antireflux therapy. Possible predictors of asthma response include patients with symptomatic esophageal regurgitation; abnormal proximal esophageal acid exposure; and, in surgical studies, those with normal esophageal motility and asthma response with medical therapy. Future research will further define the association between asthma and gastroesophageal reflux.

Relationship and comparison of selected anthropometric measures to muscular endurance and strength in children aged 3-5 years.

This study investigated the relationships and differences between grip strength, hang time (upper body muscular endurance), sum of skinfold measures, body weight and height among 103 children 3-5 years of age. The results indicated that the only significant (P less than 0.05) difference between groups on skinfold was at the umbilical site, where the 3-year-old's measurements were larger than the 4- or 5-year-old group. All strength and body weight measures increased with age and in each case were significantly (P less than 0.01) different between groups. Analysis of the correlation matrix representing key variables revealed no correlations which could be regarded as high practical indicators; thus it was concluded that body weight, height, and selected skinfold measurements were not practical indicators of grip strength and muscular endurance.

Predicting joint moments and angles from EMG signals.

Electromyographic (EMG) signals are a direct reflection of muscle activity. Efforts have been made to extract additional information from them regarding the kinematic results of muscle use, with limited success. The purpose of this study was to conduct a wheelchair propulsion experiment using a limited number of subjects to gather information for developing a neural network model to correlate EMG signals to kinematic features of the wrist, elbow, and shoulder joints. The trained model was used to predict joint dynamics from previously unseen EMG data. EMG signals were collected from four muscle groups while five able-bodied subjects propelled a wheelchair. The procedure was videotaped with the kinematics and dynamics of the three joints obtained by digitizing and transforming the images into numerical data. A neural network model, based on the back-propagation algorithm, was built and trained on the collected data. The net's predicted values were close to the observed values, particularly for the joint moments (within 7% of actual values). The results demonstrate the potential of neural networks for predicting the movement patterns of wheelchair users from a small number of subjects.

Development of an underwater weighing system for determining body composition.

A system was developed to reduce some of the difficulties associated with hydrostatic (underwater) weighing, specifically the need for complete exhalation and the subjective approximation of weighing scale measurements. The exhalation portion of the weighing protocol is particularly difficult for many disabled individuals and has contributed to the lack of available body composition information for this population. The components of our system include a computer system, load cell, spirometer, breathing tube, logic and signal conditioning circuitry specially constructed for this system, and a software package developed for this project. In a preliminary test, the body fat percentages of fourteen subjects (six males and eight females, ages 21-32 years) were determined both with the standard method and with our system. A correlation of r = 0.967 was found between the two methods, with our system's precision ranging from 1.0 to 1.3 body fat percentage points. The system could be used, for example, in developing a database for monitoring an individual's fitness or for making comparisons between groups (such as athlete to non-athlete).