Other than death due to external causes (e.g., motor vehicle accident, violence), respiratory complications have consistently been among the two leading causes of death in persons with SCI when considered after the first year post-injury, and the highest cause of death within the first year post-injury, over the past 35 years within the US Model Systems database (DeVivo et al. 1999). As noted in SCIRE Chapter: Respiratory Management Following Spinal Cord Injury (Sheel et al. 2008):
“The lungs and airways do not change appreciably in response to exercise training. It is likely that exercise is not sufficiently stressful to warrant an adaptive response. This may be even more so when considering the small muscle mass used in wheelchair propulsion or arm cranking exercise. On the other hand, respiratory muscles are both metabolically and structurally plastic and they respond to exercise training. Exercise training may influence the control of breathing and respiratory sensations (i.e., dyspnea). It is generally accepted that exercise training results in a lower ventilation at any given absolute oxygen consumption or power output. This is likely due to a reduction in one or more of the mechanisms (neural and/or humoral) purported to cause the hyperpnea (increased respiratory rate) associated with exercise. As such, the positive effects of exercise training in SCI may reside in an increase in respiratory muscle strength and endurance as well as a reduced ventilatory demand during exercise.”
For more information about these and other interventions related to exercise and muscle activation related to respiratory complications, the reader is referred to SCIRE Chapter 8 – Respiratory Management Following Spinal Cord Injury (Sheel et al. 2008). In the following section, we present those specific evidence-based statements and bottom-line conclusions from this chapter related to physical activity.
Conclusions – From SCIRE Respiratory Management Following SCI
There is level 2 evidence (based on 1 prospective controlled trial) (de Carvalho et al. 2006) and level 4 evidence (based on 4 pre-post studies) (Silva et al. 1998; Sutbeyaz et al., 2005; Le Foll-de-Moro et al. 2005; Fukuoka et al. 2006) to support exercise training as an intervention that might improve resting and exercising respiratory function in people with SCI.
There is level 4 evidence (based on 1 pre-post study) (Janssen and Pringle 2008) that computer controlled electrical stimulation induced leg cycle ergometry (ES-LCE) increases the peak values of oxygen uptake, carbon dioxide production, and pulmonary ventilation.
For exercise training to improve respiratory function the training intensity must be relatively high (70-80% of maximum heart rate) performed three times per week for six weeks. Ideal training regimes have not been identified.
Inspiratory Muscle Training
There is level 1 evidence based (on 1 RCT) (Van Houtte et al. 2008), and level 4 evidence from several studies to support IMT as an intervention that might decrease dyspnea and improve inspiratory muscle function in some people with SCI.
There is limited evidence that inspiratory muscle training improves respiratory muscle strength or endurance in people with SCI.