Biomedical subjects

Alicia M Koontz

Publications and source records attributed to Alicia M Koontz.

13 recordsLinked to original sources

PubMed2006

Surface electromyography activity of trunk muscles during wheelchair propulsion.

BACKGROUND: Trunk instability due to paralysis can have adverse effects on posture and function in a wheelchair. The purpose of this study was to record trunk muscle recruitment patterns using surface electromyography from unimpaired individuals during wheelchair propulsion under various propulsion speed conditions to be able to design trunk muscle stimulation patterns for actual wheelchair users with spinal cord injury. METHODS: Fourteen unimpaired subjects propelled a test wheelchair on a dynamometer system at two steady state speeds of 0.9 m/s and 1.8 m/s and acceleration from rest to their maximum speed. Lower back/abdominal surface electromyography and upper body movements were recorded for each trial. Based on the hand movement during propulsion, the propulsive cycle was further divided into five stages to describe the activation patterns. FINDINGS: Both abdominal and back muscle groups revealed significantly higher activation at early push and pre-push stages when compared to the other three stages of the propulsion phase. With increasing propulsive speed, trunk muscles showed increased activation (P<0.0001). Back muscle activity was significantly higher than abdominal muscle activity across the three speed conditions (P<0.0005), with lower back muscles predominating. INTERPRETATION: Abdominal and back muscle groups cocontracted at late recovery phase and early push phase to provide sufficient trunk stability to meet the demands of propulsion. This study provides an indication of the amount and duration of stimulation needed for a future application of electrical stimulation of the trunk musculature for persons with spinal cord injury.

Abdominal Muscles↗

PubMed2006

Engineering better wheelchairs to enhance community participation.

With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.

Activities of Daily Living↗

PubMed2005

Virtual reality and computer-enhanced training applied to wheeled mobility: an overview of work in Pittsburgh.

Some aspects of assistive technology can be enhanced by the application of virtual reality. Although virtual simulation offers a range of new possibilities, learning to navigate in a virtual environment is not equivalent to learning to navigate in the real world. Therefore, virtual reality simulation is advocated as a useful preparation for assessment and training within the physical environment. We are engaged in several efforts to develop virtual environments and devices for mobility skills assessment and training, exercise training, and environment assessment. Virtual reality offers wheelchair users a training tool in different risk-free environments without any indoor (e.g., walls, furniture, and stairs) and outdoor (e.g., curb cuts, uneven terrain, and street traffic) physical constraints. Virtual reality technology will probably become more common in the field of assistive technology, especially given the rapid expansion of gaming technology and the continued exponential growth of computing power.

Computer Simulation↗

PubMed2005

Biomechanics and strength of manual wheelchair users.

BACKGROUND/OBJECTIVE: Previous investigations have identified muscular imbalance in the shoulder as a source of pain and injury in manual wheelchair users. Our aim was to determine whether a correlation exists between strength and pushrim biomechanical variables including: tangential (motive) force (Ft), radial force (Fr), axial force (Fz), total (resultant) force (FR), fraction of effective force (FEF), and cadence. METHODS: Peak isokinetic shoulder strength (flexion [FLX], extension [EXT], abduction [ABD], adduction [ADD], internal rotation [IR], and external rotation [ER]) was tested in 22 manual wheelchair users with a BioDex system for 5 repetitions at 60 degrees/s. Subjects then propelled their own manual wheelchair at 2 speeds, 0.9 m/s (2 mph) and 1.8 m/s (4 mph), for 20 seconds, during which kinematic (OPTOTRAK) and kinetic (SMARTWHEEL) data were collected. Peak isokinetic forces in the cardinal planes were correlated with pushrim biomechanical variables. RESULTS: All peak torque strength variables correlated significantly (P < or = 0.05) with Ft, Fr, and FR, but were not significantly correlated with Fz, FEF, or cadence. Finally, there were no relationships found between muscle strength ratios (for example, FLX/EXT) and Ft, Fr, FR, Fz, or FEF. CONCLUSION: There was a correlation between strength and force imparted to the pushrim among wheelchair users; however, there was no correlation found in wheelchair propulsion or muscle imbalance. Clinicians should be aware of this, and approach strength training and training in wheelchair propulsion techniques separately.

Adult↗

PubMed2004

Manual wheelchair pushrim dynamics in people with multiple sclerosis.

OBJECTIVES: To define differences in pushrim dynamics during manual wheelchair propulsion by users with multiple sclerosis (MS) relative to 2 control groups of subjects with spinal cord injury (SCI) and no disability (ND) and to investigate changes in propulsion biomechanics at different speeds and with fatigue. DESIGN: Case-control. SETTING: Biomechanics laboratory. PARTICIPANTS: A convenience sample of 42 people, 8 women and 6 men per group. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The propulsion pattern, mean maximum speed, percentage of time in push and recovery phases, push angle, push frequency, mean maximum resultant pushrim force, mean work and push cycle, and hand-to-pushrim coupling and decoupling effects. RESULTS: The MS groups tended to use an arcing propulsion pattern more than did the control groups (Pmax=.003). The MS group pushed at a lower mean maximum velocity (v) when allowed to choose the speed of propulsion (v(MS),.67+/-.20m/s; v(SCI), 1.10+/-0.23m/s; P=.001), when asked to push at 1m/s (v(MS),.91+/-.26m/s; v(SCI), 1.12+/-0.11m/s; v(ND), 1.05+/-0.13m/s; P=.010), and were unable to maintain a self-selected speed during a 5-minute trial (Deltav(MS),.15+/-.02m/s; Deltav(ND),.03+/-.06m/s; P<.001). The MS group spent a higher proportion of time in the push phase of propulsion (Pmax=.001). In general, the MS group had smaller push angles, but push frequencies similar to the controls. Statistically adjusted MS group pushrim forces and work per push measures varied depending on context, but in all trials the MS group displayed a braking effect when grasping and releasing the pushrim. The MS group had declines in most measures when pushing at a self-selected speed for 5 minutes. In all trials, the MS group was more likely to display asymmetry between right and left sides in biomechanic parameters. CONCLUSIONS: Manual wheelchair users with MS have difficulty grasping and releasing the pushrim and maintaining speed during a fatigue trial. This likely leads to a slow self-selected speed of propulsion that may not be functional. Clinicians should remember these results when prescribing manual wheelchairs for people with MS.

Acceleration↗

PubMed2004

Relation between median and ulnar nerve function and wrist kinematics during wheelchair propulsion.

OBJECTIVE: To investigate the relation between median and ulnar nerve health and wrist kinematics in wheelchair users. DESIGN: Case series. SETTING: Biomechanics laboratory and electrodiagnostic laboratory at a Veterans Health Administration medical center and a university hospital, respectively. PARTICIPANTS: Thirty-five people with spinal cord injury who use manual wheelchairs. INTERVENTION: Subjects propelled their own wheelchair on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanic data were obtained by using force and moment sensing pushrims and a kinematic system. Bilateral median and ulnar nerve conduction studies were also completed. MAIN OUTCOME MEASURES: Wrist flexion, extension, radial and ulnar deviation peaks, and ranges of motion (ROMs) as related to median and ulnar motor and sensory amplitudes. A secondary analysis included peak pushrim forces and moments and stroke frequency. RESULTS: There was a significant, positive correlation between flexion and extension ROM and both ulnar motor amplitude (r=.383, P<.05) and median motor amplitude (r=.361, P<.05). CONCLUSIONS: Contrary to our hypothesis, subjects using a greater ROM showed better nerve function than subjects propelling with a smaller ROM. Subjects using a larger ROM used less force and fewer strokes to propel their wheelchairs at a given speed. It is possible that long, smooth strokes may benefit nerve health in manual wheelchair users.

Adolescent↗

PubMed2003

Shoulder magnetic resonance imaging abnormalities, wheelchair propulsion, and gender.

OBJECTIVE: To investigate the relationship between pushrim forces and the progression of shoulder injuries in manual wheelchair users. DESIGN: Longitudinal case series. SETTING: Biomechanics laboratory and magnetic resonance imaging (MRI) facility at a Veterans Health Administration medical center and university hospital, respectively. PARTICIPANTS: Fourteen individuals with spinal cord injury (8 men, 6 women) who used manual wheelchairs. INTERVENTION: Subjects propelled their own wheelchairs on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanical data were obtained by using force and moment sensing pushrims at time 1. Bilateral shoulder MR images were also completed on 2 occasions, at time 1 and, approximately 2 years later, at time 2. MAIN OUTCOME MEASURES: The peak pushrim forces in a pushrim coordinate system were calculated, weight normalized and averaged over 5 strokes (presented as % body weight). MRI abnormalities were graded by using a summated scale. Differences between scores between times 1 and 2 were calculated. RESULTS: Subjects were divided into 2 groups based on change in MRI score. Seven subjects were in the group with worsening scores (MRI+; mean, 8.14 points; range, 5-16), and 7 were in the group with improving or unchanging scores (MRI-; mean, -1.00 point; range, -5 to 1). There was no significant difference between groups with respect to age, body mass index, or years from injury. There were significantly more women in the MRI+ group (6 women, 1 man) than in the MRI- group (7 men) (P=.001). The MRI+ group used significantly greater weight-normalized radial force, or force directed toward the axle at time 1, to propel their wheelchairs at each speed (P<.01): MRI+ at 0.9m/s (mean radial force +/- standard deviation, 5.2%+/-1.0%) and MRI- at 0.9m/s (mean radial force, 3.2%+/-1.7%) (P=.028); and MRI+ at 1.8m/s (mean radial force, 6.6%+/-1.2%) (P=.023) and MRI- at 1.8m/s (mean radial force, 4.1%+/-2.2%). In a separate analysis, women were found to propel with a significantly higher radial force. A logistic regression found a significant relationship between radial force at time 1 and increased risk of progression of MRI findings over time. CONCLUSION: Individuals who propel with a greater percentage of force directed toward the axle were at increased risk of progression of MRI findings over time. Most people in this group were women. Clinicians should instruct wheelchair users in effective propulsion techniques and should pay particular attention to women who use wheelchairs. Reducing forces during wheelchair propulsion may minimize the likelihood of developing shoulder injuries.

Adult↗

PubMed2003

Range of motion and stroke frequency differences between manual wheelchair propulsion and pushrim-activated power-assisted wheelchair propulsion.

BACKGROUND/OBJECTIVE: The objective of this study was to examine the use and efficacy of a pushrim-activated power-assist wheelchair (PAPAW) in the reduction of upper extremity range of motion (ROM) and stroke frequency in manual wheelchair users. METHODS: Ten manual wheelchair users were evaluated using a repeated-measures design with and without the use of a PAPAW for maximum ROM of shoulder flexion/extension, abduction/adduction, internal/external rotation, and horizontal flexion/extension; elbow flexion/extension; wrist flexion/extension, supination/pronation, and ulnar/radial deviation; and stroke frequency. Participants propelled a Quickie 2 manual wheelchair configured as a PAPAW and their own wheelchair on a computer-controlled dynamometer at 3 different resistance levels and 2 different speeds. RESULTS: The use of the PAPAW significantly (P < 0.05) decreased shoulder flexion/extension and horizontal flexion/extension, elbow flexion/extension, and wrist flexion/extension and ulnar/radial deviation for many speed and resistance combinations. Univariate analysis revealed that stroke frequency was unaltered in all cases. CONCLUSION: These findings provide the foundation for studying the utility of the PAPAW in reducing the risk of upper limb injury and neuropathy in the manual wheelchair user population.

Adult↗

PubMed2003

Proper propulsion.

Explore the source record for details and available documents.

Equipment Design↗

PubMed2002

Propulsion patterns and pushrim biomechanics in manual wheelchair propulsion.

OBJECTIVES: To classify stroke patterns of manual wheelchair users and to determine if different patterns of propulsion lead to different biomechanics. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Thirty-eight individuals with paraplegia who use manual wheelchairs for mobility. INTERVENTION: Subjects propelled their own wheelchair on a dynamometer at 2 different steady state speeds. Bilateral biomechanical data were obtained by using a force and moment sensing pushrim and a motion analysis system. MAIN OUTCOME MEASURES: The propulsive stroke of each participant for each speed and side was classified as following 1 of 4 patterns. These 4 patterns were then compared by using a mixed-model analysis of variance. The biomechanical variables that were compared were cadence, peak and rate of rise of the resultant force, mechanical effective force, push angle, and ratio of time spent pushing to time in recovery. RESULTS: The most common propulsive stroke involved the user lifting the hand over the pushrim during the recovery phase. The stroke pattern was independent of axle position and varied from side to side and between speeds. After controlling for subject characteristics, significant differences were observed between stroke patterns in cadence and ratio of time spent pushing to time in recovery. A stroke pattern that involves using a semicircular motion with the hand below the pushrim during the recovery phase of the propulsion stroke was associated with a lower cadence and more time spent in the push phase relative to the recovery phase. CONCLUSION: The semicircular motion of propulsion displayed characteristics consistent with reduced repetition and more efficient propulsion. Use of this propulsion style may reduce trauma to the upper extremities. Clinicians should consider training individuals in this propulsion style.

Adult↗

PubMedDate not supplied

Pushrim biomechanics and injury prevention in spinal cord injury: recommendations based on CULP-SCI investigations.

Over 50 percent of manual wheelchair users with spinal cord injury (SCI) are likely to develop upper-limb pain and injury. The majority of studies related to pain have implicated wheelchair propulsion as a cause. This paper draws from a large multisite trial and a long-standing research program to make specific recommendations related to wheelchair propulsion that may decrease the risk of upper-limb injury. The studies include over 60 subjects over 1 yr after a traumatic SCI below the second thoracic level. Specific aspects of the propulsive stroke that may relate to injury include cadence, magnitude of force, and the pattern of the hand during the nonpropulsive part of the stroke. Lower peak forces, slower cadence, and a circular propulsive stroke in which the hand falls below the pushrim during recovery may help prevent injury. In addition, wheelchair users should use the lightest weight adjustable wheelchair possible. Future work should include interventional trials and larger studies that allow for more complex statistical models that can further detail the relationship between wheelchair propulsion, user characteristics, and upper-limb injuries.

Adult↗

PubMedDate not supplied

A kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces.

The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces. Eleven manual wheelchairs were fitted with a SMART(Wheel) and their users were asked to push on a course consisting of high- and low-pile carpet, indoor tile, interlocking concrete pavers, smooth level concrete, grass, hardwood flooring, and a sidewalk with a 5-degree grade. Peak resultant force, wheel torque, mechanical effective force, and maximum resultant force rate of rise were analyzed during start-up for each surface and normalized relative to their steady-state values on the smooth level concrete. Additional variables included peak velocity, distance traveled, and number of strokes in the first 5 s of the trial. We compared biomechanical data between surfaces using repeated-measures mixed models and paired comparisons with a Bonferroni adjustment. Applied resultant force (p = 0.0154), wheel torque (p < 0.0001), and mechanical effective force (p = 0.0047) were significantly different between surfaces. The kinetic values for grass, interlocking pavers, and ramp ascent were typically higher compared with tile, wood, smooth level concrete, and high- and low-pile carpet. Users were found to travel shorter distances up the ramp and across grass (p < 0.0025) and had a higher stroke count on the ramp (p = 0.0124). While peak velocity was not statistically different, average velocity was slower for the ramp and grass, which indicates greater wheelchair/user deceleration between strokes. The differences noted between surfaces highlight the importance of evaluating wheelchair propulsion ability over a range of surfaces.

Adult↗

PubMedDate not supplied

Filter frequency selection for manual wheelchair biomechanics.

Wheelchair locomotion is an important form of mobility for many individuals with spinal cord injury. However, manual wheelchair propulsion can lead to upper-limb pain and can be very inefficient. This has led investigators to apply biomechanics to the study of wheelchair use. The objectives of this study were (1) to determine the frequency content of the motion of both hands during two speeds of wheelchair propulsion, (2) to obtain the filter frequencies necessary to remove noise from wheelchair motion data, and (3) to provide signal-to-noise ratio data for wheelchair kinematics. The participants in this study were a random sample of manual wheelchair users with paraplegia caused by spinal cord injury. Subjects propelled their personal wheelchairs on a computer-controlled dynamometer at speeds of 0.9 m/s and 1.8 m/s. Motion data were collected at 60 Hz with the use of a commercial infrared marker-based system. The main outcome measures were arm motions and noise frequency spectra, filter cutoff frequencies, and signal-to-noise ratio. Our results indicate that there is no useful signal power above 6 Hz during manual wheelchair propulsion at the speeds that we analyzed. In many cases, there was no useful signal power above 4 Hz. This would indicate that the frequency content of manual wheelchair propulsion is similar to that of human gait. The mean signal-to-noise ratio varied from a high of 91 dB to a low of 21.8 dB. The signal-to-noise ratio was greatest in the x direction (along the line of progression) and lowest in the z direction (medial-lateral). Manual wheelchair propulsion kinematic data should be low-pass filtered at approximately 6 Hz for speeds at or below 1.8 m/s. The data presented in the archival literature appear to have been filtered at an appropriate frequency.

Adult↗