RESNA 26th International Annual Confence
To determine the strategies used to achieve wheelie take-off, we studied 18 wheelie-skilled subjects, using force plate and video data. We identified three primary strategies: the forward-backward-forward (FBF) strategy was used in 27 (50%) of the 54 trials, the backward-forward (BF) strategy in 22 trials (40%) and the forward only (F) strategy in 5 trials (10%). Seventy-seven percent (14 of 18) of subjects used the same strategy in all three trials. These findings have implications for wheelie training and for our understanding of the nature of this important wheelchair skill.
The wheelchair wheelie consists of three phases -- take-off, balance and landing (1,2). However, most of the previous research on wheelie performance has focused on the balance phase (1). Bonaparte et al (2), in a study on 10 able-bodied subjects, qualitatively described three methods of take-off. Po-Chou Lin et al (3) reported two distinct movements to achieve wheelie take-off, a backward movement followed by a forward displacement, resulting in the front casters lifting off the ground.
We studied 18 subjects, 10 able-bodied and 8 wheelchair users. Their mean (SD) age was 34.7 (14.7) yrs (range 19-68). Subjects were trained to perform a wheelie, success being defined by the subjects' ability to perform 3 20-s wheelies in a row. Subjects then performed 3 20-s wheelies while positioned on a force platform. Using the force plate displacement information and videotape recordings of the trials, we made observations regarding wheelie take-off. Subjective information regarding the wheelie take-off was collected from the subjects.
Wheelie take-off was accomplished be the use of one of three distinct take-off patterns (Figure 1). The forward-backward-forward (FBF) strategy was used in 27 (50%) of the 54 trials, the backward-forward (BF) strategy in 22 trials (40%) and the forward only (F) strategy in 5 trials (10%). The final forward displacement of the wheelchair, used to lift the front casters off the ground, was the only movement common to all three strategies. Seventy-seven percent (14 of 18) of subjects used the same strategy in all three trials. No subjects used all three strategies.
Subjects indicated that learning the proper technique and coordination of movement was more important than applying large amounts of force. These subjects indicated that, once they were able to coordinate the movement properly, they did not require large amounts of force to lift the front casters off the ground.
Using a backward displacement prior to the final forward thrust that initiates take-off was reported in 90% of the subjects in Bonaparte el al.'s study (2), 100% of the subjects in Po-Chow Lin et al's (3) study and in 90% of the trials in this current study. Two able-bodied subjects easily achieved wheelie take-off using a forward movement only. Similar to the 10% of subjects in Bonaparte el al.'s9 study, 10% of trials in this current study displayed this take-off pattern. Interestingly, these subjects used the largest extent of forward displacement during the take-off phase.
Subjects may select a strategy, in part, to optimally position their hands for the balance phase of the wheelie. If coordinated properly, subjects' hands are positioned near the top center of the rear wheels once balance was achieved, providing them with an adequate range to translate the wheelchair forward or backwards. The slightly flexed position of the elbow when the hands are in this position may also be advantageous with respect to the length-tension and leverage curves of the elbow flexors and extensors.
Unlike Kauzlarich & Collins (4), we observed (and many subjects commented), that producing a large force was not the limiting factor in learning wheelie take-off, but rather learning to properly coordinate the movements of the upper extremities. Understanding what is involved in optimizing wheelie take-off may help to improve training, particularly in older patients who may have heavier wheelchairs and decreased muscular strength.
James Bonaparte, C/o:
Dr. RL Kirby
Queen Elizabeth II Health Sciences Centre
Rehabilitation Centre Site
1341 Summer Street
Halifax, NS, B3H 4K4
Phone: (902) 473-1268