Visual imagery and perceived pain
As a consequence of prolonged muscle contraction, acute pain arises during exercise as a result of a build-up of noxious biochemical in and around the muscle. This could have negative consequences for the individual’s physical activity level and/or training stimulus. If pain perception could be offset during exercise, this could result in individuals having an increased willingness to either increase their exercise intensity or continue exercise for a longer period of time.
In this study, we investigated how VR and Altered Visual Feedback Strategy (AVFS) may affect the perception of exercise-induced pain among healthy people. In particular, using a low-cost VR technology, we examined how our material expectations influence our perception of task difficulty and our exercise performance. We argue that specific visual cues, e.g., the size of the object in weight lifting exercises, may reduce acute pain experienced during exercise.
The VR system was developed using Unity3D 5 to work with Samsung Gear VR and Samsung Galaxy S6 phone (see fig. below). The system we developed allows the researchers to customize the VR scenarios, including the gender of the human body, dominant hand, skin colors, colors of the t-shirt, and the weights of the barbells. In order to create a sense of embodiment, we used Microsoft Band’s gyroscope to animate the virtual arm, reflecting the movement of participant’s arm (rotation X and Y).
30 participants were assigned into three sessions: the control session where they were lifting a weight visualised correctly in VR, understate session where VR visualisation of the weight was smaller than the actual weight, overstate session where VR visualisation overstated the actual weight.
We found that when vision understated the real weight, the time to exhaustion was 2 minutes longer. Furthermore, participants’ heart rate was significantly lower by 5-7 bpm in the understated session. We concluded that visual-proprioceptive information modulated the individual’s willingness to continue to exercise for longer, primarily by reducing the intensity of negative perceptions of pain and effort associated with exercise. This result could inform the design of VR aimed at increasing the level of physical activity and thus a healthier lifestyle.