Autonomic function as a missing piece of the classification of Paralympic athletes with spinal cord injury

Objective:When someone suffers a spinal cord injury (SCI) many organs, including those of the cardiovascular (CV) system, cease to be controlled by the autonomic nervous system (ANS). Response to physical activity fails to meet the needs of the body and typically results in low blood pressure (BP), and in turn, reduced endurance and performance. This study examines the effect of SCI on the ANS of elite athletes and possible effect on their CV functions and ultimately their performance. The study also provides input on evidence of boosting and the current classification system. Finally, authors are exploring a possibility for future research in assessing whether consideration of ANS function would strengthen current Paralympic classification systems. Study design: MEDLINE, SportDiscus, Embase databases and the official Paralympic website were reviewed. In total, 60 manuscripts and five website documents were reviewed. Result: Athletes with high-level SCI affecting the ANS have limited ability to regulate their heart rate and BP in response to exercise. According to current Paralympic classification systems, these athletes are grouped with competitors who have similar motor control but intact ANS, thereby potentially putting them at a disadvantage within their own classification category. High-level SCI athletes with ANS dysfunction are also the only athletes who experience episodes of autonomic dysreflexia (AD). Whereas AD is a state of uninhibited sympathetic discharge, it is called 'boosting' when intentionally induced during competition. Boosting has been shown to improve sporting performance but can also cause serious complications due to extreme rises in BP. Therefore, boosting has been banned by the International Paralympic Committee (IPC). Despite this ban some elite high-level SCI athletes continue to boost. The IPC recognizes that the current classification systems are not the gold standard and further work is needed to create a more evidence-based classification. Conclusions: Further research is needed to determine if the inclusion of ANS parameters contributes to strengthen classifications systems in Paralympic sports. This includes the development of a simple, valid and reliable bedside assessment of autonomic function that can be used to reliably compare athletes with or without ANS dysfunction thereby enabling further research into the isolated effect of ANS dysfunction on sporting performance. Researchers who are studying individuals with SCI, and who have CV parameters as their outcomes, should ensure a homogenous study group by the presence or absence of ANS function in addition to level of lesion so as to eliminate the potential for confounding variables that lead to inaccurate interpretation of results. Spinal Cord (2011) 49, 768-776; doi: 10.1038/sc.2011.2; published online 1 March 2011