M.K. MACGILLIVRAY a,1, B. SAWATZKYa, T. LAM a, P. ZEHR b
aUniversity of British Columbia
bUniversity of Victoria
Abstract. Introduction: Approximately 155, 000 Canadians depend on manual wheelchairs for locomotion [1] and an estimated 31-73% of these people will experience shoulder pain as a result of manual wheeling [2]. Biomechanical research into the determinants of shoulder pain has been inconclusive. However, to date there has been very little research into the neural control of manual wheeling.
One concept is that rhythmic upper limb movement (such as arm swing, swimming, and possibly manual wheeling) is regulated by a central pattern generator (CPG) and follows a similar pattern of sensory processing as described for walking. This study will explore this concept by investigating the modulation of cutaneous reflexes during manual wheeling. Purpose: The purposes of this study are to determine if the cutaneous reflex response to stimulation of the superficial radial nerve are phase-dependent during manual wheeling, to determine if there is evidence of task specificity between manual wheeling and upper arm cycling and to determine if manual wheeling experience changes the pattern of reflex modulation during wheeling. Methods: Subjects will include 15 manual wheelchair users (MWUs) with spinal cord injury and 15 non-MWUs. All subjects will complete two tasks in a randomized order including wheeling on a wheelchair treadmill at a self-selected speed and arm cycling using an arm ergometer.
Electrical stimulation of the superficial radial nerve will be conducted pseudorandomly throughout the wheeling cycle eliciting cutaneous reflex responses. EMG responses will be measured in 6 muscles. The wheeling cycle will be broken up into phases using a custom made program utilizing SmartWheel and Optotrak data. Cutaneous reflex responses will be grouped and averaged depending on the phase of the wheeling cycle and be compared between MWUs and non-MWUs. Anticipated Results: It is anticipated that that the difference in cutaneous reflex amplitude between stimulated and un-stimulated EMG responses will vary dependending on the phase of the wheeling cycle. It is also anticipated that task-dependency will be evident by greater amounts of cutaneous reflex modulation of the wheeling task compared to the arm cycling task and that a greater amount of modulation will be observed in the MWU group compared to the non-MWU group.
Keywords. biomechanics, neuromechanics, manual wheelchair, shoulder injury, wheeling strategies, cutaneous reflex response, modulation, latency.
1. Introduction
Manual wheelchair use is one of the most common and more permanent forms of adapted mobility. There are an estimated 155,000 Canadians living in private
1 Megan MacGillivray: MSc Candidate, School of Human Kinetics, University of British Columbia, Vancouver, British Columbia, Canada; E-mail: [email protected]
Rehabilitation: Mobility, Exercise and Sports L.H.V. van der Woude et al. (Eds.)
IOS Press, 2010
© 2010 The authors and IOS Press. All rights reserved.
doi:10.3233/978-1-60750-080-3-45
45
households who require a wheelchair [1]. One of the largest populations using manual wheelchairs is people with spinal cord injuries. More than 41,000 Canadians are living with a spinal cord injury (SCI) with approximately 1100 new cases each year (Rick Hansen Foundation).
Although wheelchairs offer a means to improve mobility for people with lower limb disabilities, many manual wheelchair users will experience shoulder pain throughout their lives as a result of some element of wheelchair use. Manual wheeling as well as other wheelchair related tasks are thought to contribute to shoulder injury and pain. Any loss of upper arm function or associated problems places the independence of a manual wheelchair user at risk [3,4]. Previous studies have shown that anywhere from 31% to 73% of spinal cord injured MWUs will experience shoulder pain [5,2]. It has also been found that people who begin using manual wheelchairs as children report less shoulder pain than people who began using wheelchairs as adults during adulthood [6].
There is inconclusive evidence for possible biomechanical correlates to shoulder pain and it remains unclear whether there is a ‘preferred’ wheeling pattern for minimizing injury. To date, the majority of research has focused on the biomechanics of propulsion rather than understanding the neural strategies underlying manual wheeling. Studies to investigate the neural mechanisms underlying wheeling will help further our understanding of how the nervous systems adapts to long-term wheelchair use and provide a new perspective on rehabilitation training for manual wheelchair users.
Neural control, potentially consisting of a central pattern generator (CPG) or series of CPGs, of the upper limbs has been explored over the past decade. Rhythmic upper limb movements are of particular interest because they are thought to be vestigial movements maintained from an early evolutionary quadrupedal form of gait. Similar to what has been observed during walking, the processing of sensory input from cutaneous receptors in the upper limbs during rhythmic movement also exhibits phase dependent and task-dependent modulation.
2. Purpose
The purposes of this study are to (1) DETERMINE whether there is phase-dependent modulation of the cutaneous reflex response to electrical stimulation of the superficial radial nerve during manual wheeling (2) DETERMINE whether the cutaneous reflex response to electrical stimulation of the superficial radial nerve is task-specific between manual wheeling and upper limb cycling (3) INVESTIGATE the effects of manual wheeling experience on the pattern of reflex modulation in response to electrical stimulation of the superficial radial nerve.
3. Methods
Fifteen MWUs and 15 able-bodied subjects will be studied. All subjects will be a minimum of 19 years of age and capable of wheeling at a self-selected comfortable pace for 5 minutes without stopping. All subjects will be in good health. MWUs must have a history of spinal cord injury (due either to congenital or traumatic lesion) below T1. MWUs will also have spent a minimum of one year in a wheelchair.
A motion analysis system (Optotrak 3020) will be used to record sagittal-plane upper limb kinematics on the right side of the body during wheeling. The marker on the
M.K. MacGillivray et al. / The Cutaneous Reflex Response During Manual Wheeling 46
3rd metacarpophalangeal joint will be used to define the wheeling strategy for each subject. EMG data will be collected on the right side of the body from the anterior, medial and posterior deltoids, triceps, biceps, and flexor carpi radialis.
The superficial radial nerve will be pseudorandomly electrically stimulated on the right side of the body not more than once per movement cycle. For each participant the radiating threshold will be identified. The stimulus amplitude for the experiment will be delivered at 2 times the radiating threshold.
The SmartWheel (Three Rivers Holdings, Inc., Mesa, AZ) will be attached to the right side of the wheelchair. The SmartWheel will be used to collect the 3-dimensional forces applied to the pushrim.
Custom-written software in MATLAB (Mathworks, Natwick, MA) will be used to separate the data into individual wheeling cycles. Data will then be separated into stimulated and non-stimulated trials. Both the stimulated and non-stimulated data will further be broken up into 8 bins (sections) for both arm cycling and wheeling trials.
Subtracted EMG traces (non-stimulated response subtracted from the stimulated response) will be calculated for each bin and analyzed for phase dependency. A Modulation Index (subtracted EMGmax - Subtracted EMGmin)/EMGmax*100) will be calculated for early, middle and late cutaneous reflex response for each group (WMUs and able-bodied subjects) and each condition (manual wheeling and arm cycling).
4. Preliminary Data
Preliminary analysis has suggested that there is evidence of phase-dependent modulation. Further exploration will explore this concept more in-depth and determine if there is evidence of task specificity for manual wheeling.
References
[1] M. Shields, Use of wheelchairs and other mobility support devices, Health Reports/ Statics Canada 15 (3) (2004), 37-41.
[2] M.L. Boninger et al. Propulsion patterns and pushrim biomechanics in manual wheelchair propulsion, Arc Phys Med Rehabil 83 (5) (2002), 718-723.
[3] K.A. Curtis et al. Reliability and validity of the Wheelchair User's Shoulder Pain Index (WUSPI).
Paraplegia 33 (10) (1995), 595-601.
[4] W.E. Pentlans and L.T. Twomey. Upper limb function in persons with long term paraplegia and implications for independence: Part II. Paraplegia 32 (4) (1994), 219-224.
[5] K.A. Curtis et al. Shoulder pain in wheelchair users with tetraplegia and paraplegia. Arch Phys Med Rehabil 80 (4) (1999), 453-457.
[6] B.J. Sawatzky et al. Prevalence of shoulder pain in adult- versus childhood-onset wheelchair users: a pilot study. J Rehabil Res Dev 42 (2005), 1-8.
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