In the acute phase of rehabilitation, the person with a SCI has a reduced physical capacity because of muscle weakness, loss of autonomic control below the level of injury, reduced activity and subsequent changes in metabolic and vascular function (Haisma et al. 2006). The inability to reach one’s maximum potential will result in an increased risk of medical and secondary complications and has been correlated to a reduced level of functioning and quality of life. One of the important goals of rehabilitation is to reverse the debilitative cycle of reduced physical capacity that leads to reduced activity and functioning (Haisma et al. 2006). With shorter hospital lengths of stay, individuals with a SCI have fewer training opportunities. It is important to determine whether people with SCI can maintain their levels of physical capacity after discharge.
There are very few evidence-based analyses of the effectiveness of specific exercise therapies (Sipski & Richards 2006). Most research has only focused on one component of physical capacity (e.g., peak oxygen uptake [VO2 peak], or muscle strength, or respiratory function).
Many physical factors have been associated with optimal functional independence individual post-SCI and muscle strength is identified as an important contributor to functional independence (Drolet et al. 1999). Studies by Noreau et al. (1993), Marciello et al. (1995) and Durand et al. (1996) all noted a correlation between the level of the lesion, performance in functional abilities in relationship to peak oxygen intake and level of muscle strength. These associations were significant in individuals with tetraplegia especially in areas of sitting balance, spasticity of the lower limb, hand-grip strength, wrist extensor strength and global upper extremity strength. These functional areas have also been related to Functional Independence Measure (FIM) motor and self-care scores. It was also identified that upper extremity strength must be adequate to support the body weight during transfers and lower limb strength for walking. Optimal recovery of muscle strength following a SCI is an essential objective of functional rehabilitation of individuals with a SCI (Drolet et al. 1999).
Changes in motor function observed six months after an injury may be partially explained by collateral sprouting within the spinal cord (Mange et al. 1990). Changes between 2 and 8 months may be related to peripheral nerve sprouting and muscle fiber hypertrophy after partial denervation (Mange et al. 1990; Yang et al. 1990). Natural muscle strength recovery may occur up to two years post injury, with the recovery rate being more important for the first six months as measured by manual muscle testing (Ditunno et al. 1992; Mange et al. 1992; Waters et al. 1993). Muscle strength gains have been attributed to two different mechanisms in healthy subjects. In healthy subjects, short-term gains (2-4 weeks) might be explained by improved capacity to recruit motor units (neural adaptation) and gains observed after 4 weeks have been attributed to morphological changes within the contractile tissue inducing muscle fiber hypertrophy (Sale 1988). Additional studies regarding cardiovascular and exercise interventions are discussed in the Cardiovascular chapter and Physical Activity chapter.
The five studies presented address the long-term change of upper limb strength after the spinal cord injured person has returned to community living. Needham-Shophire et al. (1997) found that Neuromuscular stimulation (NMS)-assisted exercise ergometry alone and in combination with voluntary arm crank exercise was effective for strengthening of the upper limb for SCI injured individuals well after injury (mean time since injury 3 years).
Hicks et al. (2003) demonstrated all study participants had progressive increases in muscle strength in each of the muscle groups tested and that the change scores were significant from the control group except for the left anterior deltoid. Study participants self-reported decreases in stress, pain, depression, enhanced physical self-concept and overall quality of life.
Drolet et al. (1999) conducted one of the first longitudinal studies published in muscle strength changes in individuals with SCI during rehabilitation. Significant improvement of muscle strength during rehabilitation for individuals with both paraplegia and tetraplegia was noted. Significant improvements were noted at the three-month post discharge evaluation period with the tetraplegia group in the four muscle groups (elbow flexors and extensors and shoulder flexors and extensors) and then began to plateau. One year later elbow flexors showed significant improvement in both paraplegia and tetraplegia groups and shoulder extension showed significant gains only on individuals with paraplegia. Large variability was noted indicating the recovery of strength may be influenced by a variety of individual factors such as level and severity of injury, associated health conditions, age, gender, motivation and physical condition before SCI. Improvements in strength realized in rehabilitation continue to be maintained or improved when the person with a SCI returned to community living.
Haisma et al. (2006) found positive changes in the different components of physical capacity both during and after inpatient rehabilitation. SCI subjects continued to improve and this study illustrates the importance of regularly assessing the physical capacity of people with SCI after discharge. It is important to create conditions (education, exercise facilities) that facilitate further improvements (Haisma et al. 2006).
Cameron et al. (1998) also reported improvements in upper limb strengths in combination with neuromuscular stimulation.
Haisma et al. (2006) and Sipski and Richards (2006) recommended further research in this area:
- Further research is needed to document benefits of exercise interventions post-SCI including optimal methods for strengthening muscles, merits of endurance versus strength training, range of motion, gait, ADL, and transfer training.
- Due to impact of body composition, age, concomitant medical problems and our limited knowledge of recovery post SCI, research needs to be performed through well-designed multicentre trials.
- Longitudinal studies are needed to gain more insight into the changes that occur after inpatient rehabilitation and the factors which influence these changes.
- Exercise and strengthening of the upper limb in both the acute and subacute phase of rehabilitation are important in promoting independence and prevention of injury.
There is level 2 evidence (from one randomized controlled trial; Hicks et al. 2003) that physical capacity continues to improve after 1- year post discharge.
There is level 1b evidence (from one randomized controlled trial; Needham-Shrophire et al. 1997) that neuromuscular stimulation-assisted exercise improves muscle strength over conventional therapy.
There is level 4 evidence (from one case series study; Cameron et al. 1998) that neuromuscular stimulation-assisted ergometry alone and in conjunction with voluntary arm crank exercise was an effective strengthening intervention for chronically injured individuals.
There is level 4 evidence (from one pre-post study; Drolet et al. 1999) that muscle strength continues to improve up to 15 months post hospital discharge for both tetraplegic and paraplegic individuals.
Neuromuscular stimulation-assisted exercise following a SCI is effective in improving muscle strength, preventing injury and increasing independence in all phases of rehabilitation.