Mounting evidence suggests the following: 1) persons with SCI are at an increased risk for CVD; 2) persons with SCI experience an earlier onset of CVD; 3) there is an increased prevalence of CVD in the SCI population. Similar to able-bodied individuals, physical inactivity plays a significant role in the risk for CVD in persons with SCI. In fact, the ordinary activities of daily living do not appear to be sufficient to maintain cardiovascular fitness in persons with SCI. Moreover, extremely low levels of physical activity and fitness may lead to a vicious cycle of further decline. Ultimately these changes will have significant implications for the development of CVD (and associated comorbidities) and the ability to live an independent lifestyle. It appears that SCI presents an additional risk for CVD above that observed in able-bodied individuals owing to marked physical deconditioning and injury-related changes in metabolic function (e.g., insulin resistance) (Bravo et al 2004, Myers et al 2007).

Physical activity interventions have been shown to be effective at attenuating the progression of CVD and related comorbidities. The forms of exercise interventions are varied, and the experimental data are limited in comparison to other patient populations (i.e. chronic heart failure). However, there is compelling evidence supporting the health benefits of upper extremity aerobic exercise (level 1 and 4) and FES (level 4) training (see Tables 14 and 15). For instance, there is research indicating that upper extremity exercise at a moderate-to-vigorous intensity, three days/week for at least six weeks, improves cardiovascular fitness and exercise tolerance in persons with SCI. The optimal exercise intervention for improving cardiovascular fitness remains to be determined. There is level 1 evidence (de Groot et al 2003) that high-intensity (70%–80% HRR) exercise leads to greater improvements in peak power and VO₂peak than low-intensity (50%–60% HRR) exercise. Further investigation is required to determine the relative roles that cardiac and peripheral muscle function play in the improvement of exercise capacity in persons with SCI. There is level 4 (pre-post) evidence that resistance training at a moderate intensity for at least two days/week also appears to be appropriate for the rehabilitation of persons with SCI (Cooney and Walker 1986, Jacobs et al 2001, Nash et al 2001, Mahoney et al 2005).

Table 14 : Management of the risk for cardiovascular disease in persons with spinal cord injury through aerobic exercise training interventions.

Table 15 : Management of the risk for cardiovascular disease in persons with spinal cord injury through functional electrical stimulation training interventions.

There is growing evidence (predominantly level 4) from several pre-post trials that FES training for a minimum of three days/week for two months can improve oxidative metabolism (Andersen et al 1996, Mohr et al 1997, Crameri et al 2002, Crameri et al 2004) exercise tolerance (Pollack et al 1989, Hooker et al 1992, Barstow et al 1996, Mohr et al 1997, Wheeler et al 2002, Thijssen et al 2005) and cardiovascular fitness (Pollack et al 1989, Hooker et al 1992, Barstow et al 1996, Hjeltnes et al 1997, Mohr et al 1997, Wheeler et al 2002, Thijssen et al 2005). There is limited (level 4) evidence (Ditor et al 2005a, Ditor et al 2005b) that BWSTT can improve indicators of cardiovascular health in individuals with complete and incomplete SCI.

Preliminary (levels 1b and 4) evidence indicates that aerobic and FES exercise training programs (performed 30 min/day, three days per week for eight weeks or more) are effective in improving glucose homeostasis in persons with SCI (Jeon et al 2002, de Groot et al 2003). The magnitude of change in glucose homeostasis appears to be of clinical significance for the prevention and/or treatment of type 2 diabetes in persons with SCI.

There is level 1b evidence from a  high-quality RCT (de Groot et al 2003) and several pre-post studies ((Hooker and Wells 1989, Stewart et al 2004, El-Sayed and Younesian 2005) to suggest that aerobic exercise training programs (performed at a moderate-to-vigorous intensity 20–30 min/day, three days/week for eight weeks) are effective in improving the lipid lipoprotein profiles of persons with SCI. The optimal training program for changes in lipid lipoprotein profile remains to be determined. However, a minimal aerobic exercise intensity of 70% of HRR on most days of the week appears to be a good general recommendation for improving lipid lipoprotein profile. Preliminary level 4 data also indicate that FES training (three hr/week for 14 weeks) may improve lipid lipoprotein profiles in SCI (Solomonow et al 1997).

As discussed throughout this article, a growing body of evidence supports the existence of an increased risk for CVD and CVD-related mortality in persons with SCI. Marked physical inactivity appears to play a central role in the increased risk for CVD in persons with SCI. Intuitively, exercise training should lead to significant reductions in the risk for CVD and improved overall quality of life in the SCI population. However, the relationship between increasing physical activity and health status of SCI has not been evaluated adequately to date. Based on preliminary evidence (primarily level 4), it would appear that various exercise modalities (including arm ergometry, resistance training, BWSTT, and FES) may attenuate and/or reverse abnormalities in glucose homeostasis, lipid lipoprotein profiles, and cardiovascular fitness. As such, exercise training appears to be an important therapeutic intervention for reducing the risk for CVD and multiple comorbidities (such as type 2 diabetes, hypertension, obesity) in individuals with SCI. Well-designed RCTs are required in the future to establish firmly the primary mechanisms by which exercise interventions elicit these beneficial changes. Similarly, further research is required to evaluate the effects of lesion level and injury severity on exercise prescription, such that exercise programs can be developed that address the varied needs of persons with SCI. Moreover, long-term follow-up investigations are required to determine whether training-induced changes in risk factors for CVD translate directly into a reduced incidence of CVD and premature mortality in persons with SCI.

• There is level 1b evidence (Millar et al. 2009) that BWSTT improves cardiac autonomic balance in persons with tetraplegia and paraplegia (with similar results for varying degrees of lesion level and severity).
• There is level 4 evidence that BWSTT increase peak oxygen uptake and heart rate, and decreases the dynamic oxygen cost for persons with SCI.
• Level 4 evidence (Ditor et al. 2005b) indicates that BWSTT can improve arterial compliance in individuals with motor-complete SCI.
• There is level 2 evidence (de Carvalho et al. 2006) that neuromuscular electrical stimulation gait training can increase metabolic and cardiorespiratory responses in persons with complete tetraplegia.
• There is level 1b evidence (Davis et al. 1987) that moderate intensity aerobic arm training (performed 20–60 min/day, three days/week for at least 6-8 weeks) is effective in improving the aerobic capacity and exercise tolerance of persons with SCI.
• There is level 1b evidence (de Groot et al. 2003) that vigorous intensity (70%–80% HRR) exercise leads to greater improvements in aerobic capacity than moderate intensity (50-60% HRR) exercise.
• The relative importance of changes in cardiac function and the ability to extract oxygen at the periphery in persons with SCI after aerobic training remains to be determined.
• There is level 2 evidence that hand cycling exercise increases the power output, oxygen consumption, and muscle strength in paraplegic, but not tetraplegic subjects during active rehabilitation. Conversely, there is level 4 evidence that hand cycling increases power output and oxygen consumption in tetraplegic subjects.
• There is level 4 evidence from multiple pre-post studies that FES training performed for a minimum of three days per week for two months may be effective for improving musculoskeletal fitness, the oxidative potential of muscle, exercise tolerance, and cardiovascular fitness.

• There is level 3 evidence (Jae et al 2008)that upper body exercise training can improve arterial structure and function in those with SCI.

• There is level 4 evidence from multiple pre-post studies that FES training may be effective in improving exercise cardiac function in persons with SCI.

• There is level 5 evidence that arm-cranking exercise assisted by FES increases peak power output, and may increase oxygen uptake.
• There is level 1b evidence from 1 RCT (de Groot et al. 2003) and multiple level 4 studies (Chillibeck et al. 1999; Mohr et al. 2001; Jeon et al. 2002) that both aerobic and FES training (approximately 20–30 min/day, three days/week for eight weeks or more) are effective in improving glucose homeostasis in persons with SCI.
• There is level 4 evidence from multiple pre-post studies that the changes in glucose homeostasis after aerobic or FES training are clinically significant for the prevention and/or treatment of type 2 diabetes.
• There is level 1b evidence from 1 high quality RCT (de Groot et al. 2003) to suggest that aerobic exercise training programs (performed at a moderate to vigorous intensity 20-30 min/day, 3 days per week for 8 weeks) are effective in improving the lipid lipoprotein profiles of persons with SCI.
• Preliminary evidence (level 4; Solomonow et al. 1997) also indicates that the use of a reciprocating gait orthosis with FES training (3 hours/week, for 14 weeks) may improve lipid lipoprotein profiles in SCI.