Comparison of three different models to represent the wrist during wheelchair propulsion

The development of an instrumented wheelchair propulsion testing and training device

Researchers have used several types of testing devices and training surfaces to examine wheelchair propulsion. Testing and training wheelchair users on the actual surface of interest, such as tile floors or ramps, is ideal but difficult. Devices such as treadmills, dynamometers, and ergometers allow for researchers and clinicians to observe wheelchair users in a controlled space. However, these devices often do not have the ability to realistically simulate the environment. This methodological article describes the instrumentation, development and function of a wheelchair dynamometer system, the WheelMill System (WMS), a uniquely adjustable roller system for wheelchairs. Three participants wheeled on the WMS, over a tile surface and up two different graded slopes with the SmartWheel to compare speed and forces. The WMS reasonably simulated propulsion over a tile floor, though the participants' speed was slightly faster on tile, and the peak forces for each propulsion stroke varied more on tile than on the WMS. For the slopes, the speed oscillated over a greater range and was slower, and the measured peak forces were higher than the values measured on the WMS. The WMS may have several applications, though additional studies on a greater and more diverse population are needed.

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.

Impact of a pushrim-activated power-assisted wheelchair on the metabolic demands, stroke frequency, and range of motion among subjects with tetraplegia

OBJECTIVES

To determine differences in metabolic demands, stroke frequency, and upper-extremity joint range of motion (ROM) during pushrim-activated power-assisted wheelchair (PAPAW) propulsion and traditional manual wheelchair propulsion among subjects with tetraplegia.

DESIGN

Repeated measures.

SETTING

A biomechanics laboratory within a Veterans Affairs medical center.

PARTICIPANTS

Fifteen full-time manual wheelchair users who had sustained cervical-level spinal cord injuries.

INTERVENTIONS

Participants propelled both their own manual wheelchairs and a PAPAW through 3 different resistances (slight, 10W; moderate, 12W; high, 14W) on a wheelchair dynamometer. Each propulsion trial was 3 minutes long.

MAIN OUTCOME MEASURES

Primary variables that were compared between the 2 wheelchairs were participants mean steady-state oxygen consumption, ventilation, heart rate, mean stroke frequency, and maximum upper-extremity joint ROM.

RESULTS

When using the PAPAW, participants showed a significant ( P <.05) decrease in mean oxygen consumption and ventilation throughout all trials. Mean heart rate was significantly lower when using the PAPAW for the high resistance trial. Stroke frequency was significantly lower when using the PAPAW for the slight and moderate resistances. Overall joint ROM was significantly lower when using the PAPAW.

CONCLUSIONS

For subjects with tetraplegia, PAPAWs reduce the energy demands, stroke frequency, and overall joint ROM when compared with traditional manual wheelchair propulsion.

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.

Hand rim configuration: effects on physical strain and technique in unimpaired subjects?

OBJECTIVE

Hand rim wheelchair propulsion is inefficient and physically straining. To evaluate the possibly advantageous role in this respect of three different prototype hand rim configurations (a rubber foam-coated cylindrical (II) hand rim and two profiled rubber foam-coated hand rims (wide and narrow: III, IV)), a group of 10 unimpaired subjects conducted four submaximal discontinuous wheelchair exercise tests on a computer-controlled wheelchair ergometer, thus allowing a comparison with a standard hand rim (chromium-plated round hand rim (I)).

METHODS

Apart from physiological measures (oxygen uptake, heart rate (HR), ventilation, mechanical efficiency (ME)), a subjective score for the rating of each of the hand rims was determined, as well as characteristics of the force application in the propulsion phase during each test condition. Timing parameters of the push and recovery phase were determined. Each exercise test was conducted with one of the four hand rim configurations in a counter-balanced order.

RESULTS

Analysis of variance with repeated measures (hand rim configuration, power output) revealed no significant effects (P>0.05) on any of the physiological parameters and force application characteristics for the main factor 'hand rim configuration'. Only the subjective score (scale 0-10) for rating of the hand rims proved significantly different between the round rubber (7.5+/-0.53) coated hand rim-receiving the highest score-versus the narrow rubber-coated flat profiled hand rim (5.5+/-1.72).

DISCUSSION

In this subject group and under the selected tasks and submaximal conditions of wheelchair propulsion, the studied hand rim configurations did not introduce critical shifts in the technique of (de-)coupling and power production in the push phase. As a consequence, no systematic shifts in ME are found among the different hand rim configurations. It is suggested that the biological constraints of the task overrule the possible effects of small design variations of the different hand rim configurations within the studied subject group and under the limited test conditions. The hand rim design characteristics may however be much more critical in (1) experienced wheelchair users, (2) especially those subjects with a limited hand-arm and/or trunk function and/or (3) under much more extreme conditions of daily wheelchair ambulation (i.e. turning, stopping/starting, negotiating a slope) or during peak performance. These issues clearly require continued future research. As such, the current results can be viewed as preliminary results only.