Handrim forces during wheelies performance in able-bodied and SCI subjects

Context: Manual wheelchair users must be able to carry out wheelies in order to tackle obstacles in the outdoor environment. To date, no studies have compared balance variables and forces exerted on the handrim during a stationary wheelie between able bodied and spinal cord injury subjects.Objectives: To compare the distribution of forces applied to the handrim and the center of pressure displacement during a stationary wheelie between able-bodied (AB) subjects and manual wheelchair users with spinal cord injury (SCI).Design: Prospective experimental study.Setting: A university hospital laboratory.Participants: 27 participants (14 AB and 13 SCI).Outcome Measure: Each participant performed 3 stationary wheelies of 60 s duration using a wheelchair equipped with an instrumented wheel. Two force platforms were used to calculate the displacement of the center of pressure (DCOP).Results: Median group DCOP amplitude in the anteroposterior axis was smaller and less variable in the AB (19.6 mm [8.1,49.6]) than the SCI (14.9 mm [7.6,141.1]) group. Forces applied to the handrim only differed significantly between the AB (6 N [-13.8,16.6]) and SCI groups (2.7 N [-12.1 21.9]) in the posteroanterior axis.Conclusions: The results showed that the participants with SCI exerted greater PA forces on the handrim, moreover, the direction of force was opposite to that of the AB group, suggesting that the SCI group used a proactive balance strategy while the AB group used a retroactive strategy. The results suggest that the direction of force applied should be considered when teaching individuals to perform wheelies.