Virtual Reality Balance Games Provide Little Muscular Challenge to Prevent Muscle Weakness in Healthy Older Adults

Abstract

Objective: Muscle weakness is an important risk factor for falls in older adults. Intensity and duration of muscle activity are important determinants of exercise effectiveness in combating muscle weakness. The aim of this paper was to assess the intensity and duration of muscle activity in Virtual Reality (VR) balance games. Materials and Methods: Thirty young and thirty healthy older adults played seven different VR balance games. Muscle activity of the Vastus Lateralis, Vastus Medialis, Soleus and Gluteus Medius was obtained using surface EMG. The processed EMG signals were divided in 200ms blocks, after which each block was categorized by its average normalized EMG activity i.e. >80%, 60-80%, 40-60% or <40% of maximum voluntary contraction (MVC). We calculated the total number of blocks in each category to score intensity, as well as the maximal number of consecutive blocks (MCB) >40% MVC, to identify prolonged muscle activity. Results: Muscle activity during game-play was mostly below 40% MVC and prolonged activation was lacking. Only the games that included more dynamic movements showed activation blocks of higher intensity and resulted in more MCB. Conclusion: Our method allowed us to analyze the overall muscle activity and the distribution of activity over a trial. Although the activation levels during these VR games were low in general, we identified game elements that could potentially provide a strength training stimulus. Future research should aim to implement these elements, such that the intensity, prolonged activity and rest are optimized to sufficiently challenge lower limb muscles in VR training.

Does a novel exergame challenge balance and activate muscles more than existing off-the-shelf exergames?

“…The remaining two were off-the-shelf games: Adventure, Kinect Adventures (Ubisoft, Rennes, France) and Kinski, Kinect sports season 2 (Microsoft Studios, Redmond, WA, US). Adventure and Kinski were included in this study because they showed to be the games that previously had most induced muscle activity and weight shifts [22,24].…”

“…Based on the recommendations for balance and strength training, obtained from the literature [2,6,18,27] and our previous work in training using exergames [22,24,25], several concepts to be addressed in exergames balance training applications were proposed. In Fig.…”

“…EMG signals from both experimental and maximal voluntary contractions (MVC) trials were high-pass filtered at 20 Hz, using a 3rd order high-pass Butterworth filter, before being rectified and smoothed using a moving average technique with a time window of 100 ms. The processed signals from the experimental trials were then normalized to maximum values obtained during the MVCs [24]. Muscle activity was analyzed during the off-the-shelf game Adventure and the novel games Fishing and Garage.…”

“…Muscle activity was analyzed during the off-the-shelf game Adventure and the novel games Fishing and Garage. A short description of the post-processing methods used to quantify muscular challenge is described in more details elsewhere [24]. In short, the normalized EMG signals were divided in blocks of 200 ms. Based on the average activation in each block, each episode was then categorized in one of four activation zones, < 40%, 40-60%, 60-80 and > 80% MVC.…”

“…Moreover, it was found that adaptation to or learning the game, as trials advanced, resulted in a decreasing challenge in some games [22,23]. From the analysis of muscle activity in seven off-the shelf games, it was concluded that overall muscle activation was low and that longer periods of muscle activation were scarce [24]. Only the games that required faster movements elicited some muscle activity that seemed challenging enough to be considered as a training impulse [24].…”