Assessment of the postural control strategies used to play two Wii Fit™ videogames
Highlights
► We evaluated the balance control strategies adopted when participants played the Wii Fit™. ► Distinct strategies emerged with increased experience playing the Soccer Heading and Ski Slalom games. ► With experience centre of pressure variability increased for Soccer Heading and decreased for Ski Slalom games. ► When playing Soccer Heading participants demonstrated greater shoulder tilt. ► When playing Ski Slalom participants demonstrated increased pelvic–shoulder coupling.
Introduction
Biofeedback and virtual reality (VR) systems have been used widely in research to probe the underlying neural control mechanisms involved in the maintenance of static and dynamic stability [1], [2]. In a rehabilitation context, these systems have been used to train gait and balance control in individuals with stroke [3], spinal cord injury [4] and neuromusculoskeletal conditions [5]. The therapeutic advantages of VR are related to the ability to precisely control the features of the surrounding environment, including timing of visual, auditory and mechanical stimuli. Repeated exposure allows learning of adaptive motor control strategies in response to these stimuli. The application and feasibility of VR systems have been limited however, due to restricted availability and high costs. The advent of affordable interactive video-gaming platforms has provided the rehabilitation community an opportunity to take advantage of the potential benefit of VR based systems through an accessible platform. It is therefore of significant importance to enhance our understanding of the fundamental movements and balance control strategies that are adopted when interacting with these games.
Recently, Deustch et al. [6] reported that training with Wii Sports™, which involves interaction through hand-held motion detectors, led to improvements in visual perceptual processing, postural control, and functional mobility in an individual with cerebral palsy [6]. Although in Wii Sports™ the user-game interaction is introduced through a different effector, it is plausible that playing the Wii Fit™ videogames may lead to similar improvements in dynamic postural control. Additionally, individuals with general instability due to age-related decline in function may also benefit from playing these videogames. Further research is required to examine the postural control strategies used when playing the Wii Fit™ videogames in order to further develop clinical recommendations related to its possible application in a rehabilitation setting.
Recent studies have shown that individuals can improve postural control following practice of a motor task in a single session. In a study by Hatzitaki et al. [7], participants used a balance rehabilitation device encompassing a dual force platform with online visual feedback reflecting the force applied under each foot. It was determined that with practice the participants were better able to shift weight between the lower extremities. Similarly, Elion et al. [8], reported that centre of pressure (COP) excursion decreased during training and continued to decrease 24 h post-training, suggesting that a single balance training session was sufficient to learn and retain improved postural control strategies. Van Ooteghem et al. [9] reported that participants developed general motor processes to control centre of mass (COM) excursion rather than a specific response to the sequence of perturbations. It should be noted that short-term gains in performance may not translate to long-term retention.
While a recent investigation of the COP displacement measured from the balance board of the Wii Fit™ has demonstrated good reliability, and validity [10], and thus potential to be a useful rehabilitation tool for postural control retraining, currently there are no published literature regarding the specific balance reactions elicited by the games. As such, it is critical to examine if the games will lead to improved balance and promote appropriate dynamic postural control strategies. Furthermore, it is also imperative to determine whether or not playing the games could result in maladaptive postural control. For the present study, two of the Wii Fit™ videogames (Ski Slalom and Soccer Heading) are of particular interest. For each game, the control of the on-screen character or ‘avatar’ (Skiier, Soccer Player) is achieved through a change in weight distribution between the left and right sides of the Wii Fit™ balance board. It is hypothesized that optimal control of this game may be achieved through a ‘load/unload’ strategy that is recognized as fundamental to the control of upright stance [11]. It is within clinical populations with weight bearing asymmetry [12], [13], [14] that this control strategy is often compromised, and of clinical interest to address. However, notably, the on-screen movements of the avatar in each game are distinctively different, while the principle of avatar control remains the same (i.e., change in weight distribution through balance board). Based on literature that has examined the role of the “Mirror Neuron System” and observational learning of movement we postulated the different games would lead to distinct patterns of movement because the avatar acts as a model for movement control [15].
Thus, the objectives of the present study were:
- (1)
To evaluate the postural control strategies healthy young adults use when playing Ski Slalom and Soccer Heading games on the Wii Fit™.
- (2)
To compare the postural control strategies healthy young adults use across the first versus tenth trials of Ski Slalom and Soccer Heading games on the Wii Fit™.
We anticipated that when playing Wii Fit™ videogames, healthy young adults would utilize complex postural control strategies that vary depending on whether the games involve feedforward control (Ski Slalom) or a reaction to a visual stimulus (Soccer Heading) and the associated visual input of the avatar. We propose that with practice, healthy young adults will alter their postural control by utilizing different movement strategies of the pelvis and trunk. Specifically, shoulder and pelvic movements would become more coupled and extraneous movements (i.e., tilt and rotation) would be reduced. We also propose that over 10 trials of each game the participants would decrease the variability in COP excursion, reflecting an overall improvement in their ability to control their posture as they play the game.
Section snippets
Participants
Sixteen healthy young adults (10 female and 6 male) participated in this study. Their age ranged between 22 and 30 years of age (mean = 25, SD = 2). The mean height and mass of the participants was 1.7 ± 0.3 m and 68 ± 12 kg respectively. None of the participants self-reported more than recreational experience playing soccer or skiing. All participants self-reported normal or corrected-to-normal vision and had no previous experience with the Wii Fit™. Participants who required corrective lenses for
Centre of pressure (ML excursion)
A 2 Game (Ski Slalom, Soccer Header) by 2 Trial (first, tenth) repeated measures analysis of variance of the standard deviation of ML COP movement revealed significant main effects for game, F(1, 14) = 19.57, p < 0.05, and trial, F(1, 14) = 5.59, p < 0.05. Overall participants exhibited greater ML excursion while playing the soccer (66.7 mm) versus the ski (50.1 mm) game. Participants also decreased the ML movements from the first (62.9 mm) to the tenth trial (53.9 mm).
In addition to these main effects,
Discussion
The present study examined the postural control strategies employed by healthy young adults while playing two different Wii Fit™ games. The specific games were selected because they can be played successfully using similar body movements but involve unique visual input. Specifically, participants played 10 trials each of the Soccer Heading and Ski Slalom games on the Wii Fit™ videogame system. Over 10 trials of game play participants developed unique postural control strategies that directly
Conclusion
Overall the participants adapted a unique postural control strategy to play each videogame that was a direct reflection of the visual input of their avatar. After 10 trials, the Soccer Heading game challenged participants’ stability limit as they appeared to control their balance through a trunk strategy, rather than a lower limb strategy. Conversely, during Ski Slalom, participants increased the coupling between the shoulders and pelvis, indicating a balance strategy that involves lower
Conflict of interest statement
The author's have no conflict of interest related to this study, and have no financial or personal relationships with other people or organizations that could inappropriately influence this work.
Acknowledgements
This research was conducted in partial fulfillment of the requirement for an MScPT degree at the University of Toronto (A.M., C.G., A.M., W.W., A.K.). We would like to thank Justin Chee for his technical expertise.
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