Towards evidence-based classification - the impact of impaired trunk strength on wheelchair propulsion

Introduction: Current methods for classifying impairments in disability sports are based largely on experience and expert opinion, and are therefore of questionable validity. The International Paralympic Committee's Sports Science Committee aims to develop a new evidence based classification system based on the relative strength of association between impairment and activity limitation. Aim: The purpose of this exemplary pilot study is to illustrate the concept of relating consequences of impairment to sport-specific performance determinants in wheelchair sports. This pilot-study examined the impact of impaired trunk strength (impairment) on wheelchair acceleration from standstill (activity). Method: One able-bodied wheelchair basketball player (WB) and one wheelchair tennis player with complete T4 SCI (WT) performed a generic (non-sport-specific) and sport-specific force generation test in varying conditions regarding trunk and pelvic support. Results: The results show that including the abdominal muscles in the generic force generation muscular chain leads to a 41.41% loss of generic force generation in WB compared to 80.59% in WT. As well, including the abdominal muscles during wheelchair propulsion force generation results in a 0% loss of acceleration capacity in WB compared to 42.2% in WT. Conclusion: The current study demonstrates that the impact of pelvic and trunk strength (impairment) on one of the main determinants in wheelchair sports performance (activity) can be measured and quantified. Such knowledge will have implications for rehabilitation and classification in grass roots and elite-level sport.