A physically active lifestyle—including sports—during and after rehabilitation is becoming an increasingly important issue on the rehabilitation research agenda (Cooper et al., 1999; Rimmer and Braddock, 2002). Understanding the underlying mechanisms and processes of adaptation and/or the compensation of function and
Therefore, to improve rehabilitation protocols and wheelchair propulsion performance it is of primary importance to have a complete knowledge of the activation pattern of shoulder muscles during wheelchair propulsion. The overall purpose of this thesis was to investigate the shoulder muscle recruitment patterns and wheelchair kinetics over a range of daily activities and mobility tasks requiring manual wheelchair propulsion. With a complete understanding of the muscle recruitment patterns during wheelchair propulsion and wheelchair biomechanics, physiotherapists and
wheelchair users can improve wheelchair propulsion skills to prevent shoulder injuries and maintain comfort during locomotion. This information would also be useful for developing the strength training and rehabilitation programs for wheelchair users.
1.2.1 The specific aims
1. Isometric, eccentric and concentric contractions Hypothesis:
if the observation holds true for humans that higher and lower EMG and MMG frequencies are generated by faster and slower muscle fibre types it should be expected that the EMG and MMG signals during a ramp and step isometric and eccentric-concentric contractions would contain sequentially higher frequency components as the faster motor units become recruited. EMG and MMG spetrum may contain different information regarding motor
unit recruitment pattern during isometric, eccentric, and concentric contractions
2. To investigate how the semicircular propulsion pattern affects muscle recruitment patterns and wheelchair kinetics compared to a self-selected stroke pattern during the initial learning stage of wheelchair propulsion.
Hypothesis: a short session of instruction in the proper wheelchair propulsion technique could result in biomechanically more economical wheelchair propulsion and a better coordinated muscle recruitment pattern of the shoulder muscles.
3. To investigate the shoulder muscle recruitment patterns from unimpaired individuals during wheelchair propulsion under various propulsion conditions. Hypothesis: the motor unit recruitment patterns within individual muscles and between synergistic muscles would change with different propulsion conditions.
4. To investigate the effect of mild fatigue on changes in motor unit recruitment within individual shoulder muscles and in the coordination of shoulder muscles as well as in wheelchair kinetics.
Hypothesis: the wavelet analysis combined with principal analysis is sensitive to the muscle fatigue during fatiging wheelchair propulsion.
1.2.2 Research protocol
1.2.2.1 Recruitment of participants
The study of wheelchair propulsion is complicated by the strong variability in functionality among the disabled population. Attempts to study muscle activation in wheelchair users would likely result in large inconsistencies in activation patterns.
To initially overcome the inherent problem of the considerable heterogeneity of wheelchair users, it seems appropriate to study non-wheelchair users first, since they will be equally well trained or untrained for all tested conditions and obviously will physically be quite homogeneous(van der Woude et al., 2001). Although the results may not be completely transferable to people with SCI (Brown et al., 1990; Kamper et al., 2000; Hintzy et al., 2002), the recruitment of able-bodied participants is a useful beginning strategy for further clinical study (de Groot et al., 2003; Roux et al., 2006). The information that can be gathered from this study is a starting point for developing a future shoulder muscle recruiment pattern for wheelchair users with spinal cord injury.
In order to ascertain an appropriate sample size for this thesis a power analysis was performed. This was based on a study conducted by Kabada et al, in which they looked at the repeatability of electromyographic data from 10 muscles from both the upper and lower extremity (Kadaba et al. 1989). The mean coefficient of multiple correlation (0.8448) and standard deviation (0.0645) were used with an anticipated effect size of 10% (0.76032). To calculate the sample size the comparison of 2 means formula was utilized, with a power of 90% and a significance level of 5%. This yielded a value of 12.24 and hence 15 participants will be required for the study. Inclusion criteria:
Participants will be able-bodied participants.
of specific patients groups for which these techniques might be applied in due course. If these techniques prove effective in the convenience sample proposed, a more extensive study will be undertaken to include people with disabilities and over a representative age range.
Exclusion criteria:
Neuromuscular condition e.g. multiple sclerosis, motor neuron disease Pre-existing injury or pain during exertion in upper extremities by using PAR-
Q questionnair
Prescribed drugs for neuro-musculoskeletal pain or which have related side- effects
1.2.2.2 Choice of muscle region
The most common shoulder problem after a spinal cord injury is shoulder bursitis, also known as impingement syndrome. Neer (1972) described the impingement syndrome as compromise of the space between the humeral head and the
coracoacromial arch (Neer, 1972). In the classic case, the coracoacromial ligament and the anterior inferior aspect of the acromion are compressed against the bursal side of the rotator cuff during forward flexion of the shoulder. There have been many studies aimed at investigating the shoulder muscles, including the rotator cuff, deltoid, and scapular muscles.
In the present thesis, shoulder muscle activity was documented with surface EMG on anterior, middle, and posterior portions of the deltoid (AD, MD, PD), the pectoralis major (PM), upper trapezius (UT), and long heads of biceps brachii (BB) and triceps brachii (TB).
The rotator cuff muscles are not located superficially, so surface EMG is not suitable to detect these muscles. Wired EMG on these muscles is recommended in future studies.
1.2.2.3 Wheelchair protocol and configuration
A rigid-frame, lightweight wheelchair (Quickie GP, Sunrise Medical, Longmont, CO, USA) was used through all the propulsion trials. The configuration of the wheelchair (seat cushion, seat height, and axle position, footrest height) was the same for each participant. The right side of the test wheelchair was instrumented with a SmartWheel. The resulting moment signals were synchronized with an EMG / MMG data
acquisition system and used to identify the timing of the push and recovery phase of the propulsion cycle (PC). A custom wheelchair ergometer served as the testing platform. It consisted of a supporting frame, a data acquisition system and split rollers that obligated the participant to propel each rear wheel separately. The rear wheels of the wheelchair were positioned on the ergometer’s rollers while the wheelchair was secured to the supporting frame of the ergometer (details in Chapter 2). Before data acquisition, participants were allowed to become familiar with the ergometer by propelling the test wheelchair for several minutes.
Several studies have indicated that wheelchair configuration has a significant effect on wheelchair propulsion performance (Morrow et al., 2003; Cowan et al., 2009; Lin et al., 2009). Cowan’ study (2009) showed that the axle position relative to the shoulder is associated with significant differences in pushrim biomechanics. Hughes and associates’ (1992) tested the effect of seat position on wheelchair propulsion biomechanics. They found that biomechanics changed with seat position (Hughes et al., 1992). Lin et al (2009) found that users could produce greater propulsive moment at the position they preferred. Since the participants were inexperienced and able- bodied in the present studies, these parameters were not controlled. In future studies, we would recommend testing of individuals with SCI in their own wheelchairs.
Wheelchair user characteristics, such as height and years with SCI, or wheelchair setup would also be of concern. Kinematics should be involved in future studies to record the movement of the upper extremity.