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In recent years, many studies have associated sedentary behavior in front of screens with health problems in infants, children, and adolescents. Yet options for exergaming—playing video games that require rigorous physical exercise—seem to fall short of the physical activity levels recommended by the World Health Organization.
The purpose of this study was to investigate the effect of a fully immersive virtual reality (VR)-based training system on cardiovascular and muscular parameters of young adults.
A cross-sectional experiment design was used to analyze muscle activity (surface electromyography), heart rate, perceived exertion (RPE), cybersickness symptoms, perceived workload, and physical activity enjoyment (PACES) in 33 participants performing two 5-minute flights on a new training device.
Participants’ performance of the planking position required to play the game resulted in moderate aerobic intensity (108 [SD 18.69] bpm). Due to the mainly isometric contraction of the dorsal muscle chain (with a mean activation between 20.6% [SD 10.57] and 26.7% [SD 17.39] maximum voluntary isometric contraction), participants described the exercise as a moderate to vigorous activity (RPE 14.6 [SD 1.82]). The majority reported that they enjoyed the exercise (PACES 3.74 [SD 0.16]). However, six participants had to drop out because of cybersickness symptoms and two because of muscle pain due to prior injuries.
Our findings suggest that fully immersive VR training systems can contribute to muscle-strengthening activities for healthy users. However, the dropout rate highlights the need for technological improvements in both software and hardware. In prevention and therapy, movement quality is a fundamental part of providing effective resistance training that benefits health. Exergaming on a regular basis has the potential to develop strong muscles and a healthy back. It is essential that future VR-based training systems take into account the recommendations of sport and exercise science.
There is a growing body of evidence suggesting that a high level of sedentary behavior can harm human health [
The World Health Organization (WHO) has identified the appearance of negative symptoms due to excessive digital gaming as a disorder. Sedentary behavior spent in front of screens has been reported to increase the risk of obesity, high-density lipoprotein dysfunction, and high blood pressure, which are also major risk factors for cardiovascular morbidity [
The portmanteau word exergaming combines exercise and gaming [
Exercise can refer to the process of becoming more skilled in a set of actions, without necessarily specifying the degree of body movement involved [
Exercise can also describe physical activity involving body movements that do not promote physiological adaptation mechanisms or increase a particular skill level [
Using the term exercise interchangeably with physical activity or even physical fitness can, therefore, be misleading when referring to exergaming systems. The proposed definition by Oh and Yang [
Physical exercise includes an effective stimulation of the muscle adaptation mechanism. WHO recommends that adults between the ages of 18 and 64 years should do at least 150 minutes of moderate-intensity aerobic physical activity throughout the week, at least 75 minutes of vigorous-intensity aerobic physical activity throughout the week, or an equivalent combination of moderate- and vigorous-intensity activity. Muscle-strengthening activities should be done for major muscle groups on two or more days per week [
Different muscle contraction types can produce different gains in muscle strength and power [
In 2009, lower back pain ranked third among the most common syndromes and illnesses [
To the best of our knowledge, this is the first qualitative study to examine the muscular training potential of an immersive VR-based full-body exergaming system. The study also analyzed the impact of exergaming on the cardiovascular system and its potential to provide effective endurance training. Understanding its impact on participants’ perceived levels of motion sickness, cognitive load, and overall enjoyment could provide insight into the potential and utility of similar approaches.
Thirty-three participants (mean age 23.90 [SD 4.58] years) were recruited via social media platforms, email chains, and flyers. The study protocol was approved by the ethics committee of the German Sport University Cologne. Most of the participants were students at the German Sport University Cologne. Data collection occurred between June and August 2017. Participant requirements were defined to ensure that factors such as sex, age, and physical condition would not bias the data:
Male participants aged younger than 30 years: due to hormonal changes, women tend to be more susceptible to motion sickness than men [
Athletic body: body mass index correlates with body fat percentage, which can influence the signal quality of surface electromyography (sEMG). To get a valid sEMG signal, participants had to have a BMI <25 kg/m2, indicating a low body fat percentage.
Height between 170 and 190 cm: the Icaros device (
(A) Torso-arm angle measurement using protractor, (B) Icaros device, (C) participant being familiarized with the device, (D) upper-to-lower limb angle measurement using protractor.
The experiment protocol required a variety of different systems to be used simultaneously and synchronized for data analysis.
The Icaros VR fitness machine and flight simulator (Icaros GmbH) consists of a device and an attached gyro sensor (
The device can be rotated around the pivot point with a range of motion between –35° and 35° for roll and –45° to 45° for pitch on the vertical and sagittal axes, respectively.
The VR system employed the Gear VR headset version SM-R322 (Samsung Electronics) and gamepad for setting in-game options. The Icaros software was installed on a Galaxy S6 (Samsung Electronics) smartphone running Android 6.01. The integrated smartphone accelerometer and gyroscope paired with the head-mounted display allowed users to interact with the visual stimuli in virtual reality while maintaining their body position on the Icaros.
Participant heart rates were measured continuously using the RS800 heart rate monitor (Polar Electro).
Muscle activity was measured based on sEMG using the TeleMyo 2400T G2 (Noraxon USA).
The study employed questionnaires measuring sociodemographic and anthropometric data. The Simulator Sickness Questionnaire (SSQ) was used to assess perceived motion sickness and cybersickness symptoms during the flights. Enjoyment of the flight sessions was measured using the Physical Activity Enjoyment Scale (PACES). Results are based on the mean average of the 16-item modified version of the questionnaire ranging from a scale of 1 (strongly disagree) to 5 (strongly agree). A high score indicates a high level of physical activity enjoyment [
All participants were informed about the aim of the study and provided with a written description of the procedure. Participants completed questionnaires collecting sociodemographic and anthropometric data (
For each test, participant’s height was measured, and the distance between the Icaros arm and foot holders was configured to align the body’s center of gravity with the pitch axis’ zero degree point. The upper-to-lower limb and torso-to-arm angle were configured to 135° and 90°, respectively (seen in
In a 5-minute familiarization session, participants were introduced to the VR in-game tasks. Afterward, eight electrodes were positioned on the recommended sensor locations for the
Sociodemographic and anthropometric characteristics of study participants.
Variable | Finishers (n=25), mean (SD) | Motion sickness dropouts (n=6), mean (SD) |
Age in years | 24.16 (4.82) | 25.00 (1.90) |
Height (meters) | 1.80 (0.63) | 1.88 (0.08) |
Weight (kg) | 77.50 (8.49) | 83.00 (6.10) |
Body mass index (kg/m2) | 23.80 (2.03) | 23.36 (1.18) |
Positioning of electromyography electrodes, hardware, and software.
In-game screenshot of the participant field of view.
The captured sEMG signal was smoothed using the root mean square algorithm, and the time interval was set to 300 milliseconds [
For the purposes of data analysis, a MATLAB script was programmed to provide a time sync of the Icaros device position along with the corresponding muscle activation and heart rate.
The captured data were exported from the MATLAB environment and statistically analyzed (SPSS Statistics 23, IBM Corp).
Power analysis indicated that for an estimated effect size of 0.6 with 80% power and 5% type I error, 25 participants were needed. Flight sessions that had to stop due to muscle pain or cybersickness symptoms were excluded from all data analysis except the SSQ score.
Six participants had to stop the experiment due to signs of nausea or discomfort indicative of motion sickness. Another two participants stopped the VR flights because of muscle pain due to prior injuries. Post hoc analysis was computed based on a 5% type I error and a total of 25 participants.
A paired sample mean
Average muscle activation during the two consecutive flights.
There were significant differences between resting heart rate and heart rate during the flights (
The one-way analysis of variance with repeated measures and a Greenhouse Geisser correction showed significant differences in the three heart rate measurements
Average heart rate during flight 1 was significantly higher (
Results from the paired sample
Heart rate and rate of perceived exertion during the two flights.
Participants were able to steer pitch and roll by changing their body’s center of gravity. A paired
Downward pitch movements also showed a significant difference, with
The average degrees of roll were similar in both directions. Rolling left showed a significant difference, with
Rolling right also showed significantly higher average degrees for flight 1 (mean 5.75° [SD 2.62]) than for flight 2 (mean 4.7° [SD 1.86]), with
Heat plot of the Icaros device’s movements for both flights. Symbols depict the average positions throughout the flights on each axis.
Postsession questionnaires included the SSQ, NASA-TLX, and PACES.
Levene test indicated unequal variances for all but the nausea score. Therefore, the degrees of freedom were adjusted from 29 to 5.26 for oculomotor, from 29 to 5.31 for disorientation, and from 29 to 5.35 for the total score. Due to the different sample sizes, a weighted effect size based on Hedges’ G formula replaced the Cohen
The independent
Participants found the sessions to be very physically demanding and exerted much effort when completing the session task. The task was not perceived as mentally demanding; its pace was not perceived as hurried or rushed (temporal demand). Participants felt like they achieved very good results (performance) and didn’t feel particularly insecure, discouraged, irritated, stressed, or annoyed (frustration). Despite the high physical demand scores and the moderate to vigorous RPE scores, participants rated the flights as highly enjoyable (PACES score 3.74 [SD 0.16]).
Postsession questionnaire scores by dimension.
Questionnaire and dimension | Finishers | Motion sickness dropouts | Significance |
Effect size g | |
|
|||||
Oculomotor | 22.44 (15.85) | 87.17 (48.11) | .02 | 2.62 | |
Disorientation | 23.39 (29.72) | 146.16 (82.93) | .01 | 2.80 | |
Nausea | 27.86 (27.52) | 124.02 (34.66) | <.001 | 3.24 | |
Total score | 28.27 (21.51) | 130.90 (56.67) | .006 | 3.35 | |
|
|||||
Mental demand | 45.04 (24.61) | —c | — | — | |
Physical demand | 76.76 (15.73) | — | — | — | |
Temporal demand | 43.04 (18.73) | — | — | — | |
Performance | 74.88 (16.84) | — | — | — | |
Effort | 74.52 (10.98) | — | — | — | |
Frustration | 33.24 (24.78) | — | — | — | |
PACESd | 3.74 (0.16) | — | — | — |
aSSQ: Simulator Sickness Questionnaire.
bNASA-TLX: NASA Task load Index.
cNot available.
dPACES: Physical Activity Enjoyment Scale.
For isometric contractions, there is a good correlation between muscle activity and generated force [
Muscle activity during flights indicates the effects on muscle blood flow stimulation for all muscle groups. Kibler [
Dorsal muscle chain activity (neck extensors and lumbar region of
Participants position on the Icaros device resembles the well-established plank exercise. The only difference is the device’s shin holders, which provide additional support for users (
To achieve the most immersive experience, the virtual horizon was adjusted to a 45° angle, which required the participants to tilt their heads back. This position requires an almost constant isometric muscle contraction of the neck extensors. The neck extensors’ average muscle activation was relatively high compared with that of the
The similarity between the average muscle activations seems to indicate the potential reliability of the Icaros VR system. Being able to reproduce the physiological muscle activation in a consecutive flight suggests that familiarization effects do not reduce muscle activity straight away. Nevertheless, the long-term outcome of repetitive flights cannot be assessed based on this study’s design. The sample size consisted mainly of fit, young sport students whose athleticism distinguishes them from the general public.
Since the second flight was the same as the first one in terms of the virtualized in-game world and properties (eg, flying speed), differences between the two flights are attributable solely to participants’ movements.
The heat plot in
During the first flight, participants rolled by an average of 5.76° to the left and 5.75° to the right. Pitch movements reached 8.04° downward and 7.73° upward. Flight 2 resulted in a significantly smaller range of motion across all four directions, with effect size varying between 0.46 and 0.57. The smaller range of motion during the second flight can be attributed to familiarization with the in-game elements and device properties during the first flight.
Improved intermuscular coordination from reintroducing and sustaining body balance on the device after pitch and roll movements could also explain the significantly smaller range of motion. Interestingly, the significantly smaller range of motion did not correspond to significantly lower muscle activation during the second flight (see
Due to the mostly static position of the participants on the device, the effects on their cardiovascular system were expected to be low. Their resting heart rate (60.04 [SD 7.90] bpm) was significantly lower than their heart rate during the first (108.22 [SD 18.72] bpm) and the second (101.12 [SD 19.53] bpm) flights. Despite the significant differences between the two, the effect size was small to medium (
Although heart rate alone is an insufficient metric for measuring energy expenditure and physiological effect [
For muscle strength endurance training, long periods of muscle tension are connected with significantly higher myofibrillar protein synthesis [
The reported RPE values of 14.56 (SD 2.09) for both flights indicate a moderate to vigorous activity level. The question of whether the perceived intensity level is due to physical arousal or due to cognitive workload can be further analyzed by looking at the reported NASA-TLX values, in which mental demand is lower than physical demand. Despite the perceived medium to high exertion levels, the reported enjoyment (PACES) during the VR sessions was high (3.74 [SD 0.18]), indicating that the VR system was fun to use. The perceived exertion, task workload, and enjoyment level are good indicators of a system’s potential to provide a good combination of fun and physical activity.
Cybersickness can be described as a visually induced motion sickness that is common in immersive VR sessions [
The (forced) planking position on the Icaros was never before applied in a fully immersive VR system. It introduces high immersiveness by keeping the users on the transversal plane, simulating the in-game flying position. Changing of the visual stimuli as the device shifts on the axes is a unique feature of the system. Flights with the Icaros system seem to lead to relatively high SSQ scores in general [
The system used for our study does not represent the state of the art for head-mounted display technology, which can be found in devices such as Oculus Rift (Facebook Technologies LLC) and Vive Pro (HTC Corporation). Screen flickering caused by high latency and a low refresh rate (60 Hz) of systems like ours has been associated with symptoms of motion sickness [
Gallaghar et al [
Riccio and Stoffregen [
There are some limitations that warrant discussion. First, requirements regarding the physiological status of participants and the low fat-to-body ratio were very strict. While these requirements ensured high-quality and reliable EMG activation signals, they also restricted the transferability of the results to populations with different body compositions. Furthermore, the exclusive use of male participants for a consistent perception of cybersickness symptoms rendered the study unable to assess the physiological and psychological outcomes on female participants [
This paper tries to investigate the combination of a fully immersive VR system with physical activity through a sport-science–based approach. To the best of our knowledge, this is the first qualitative study that examines the muscular training potential of an immersive VR-based full-body exergaming system.
We use established measuring procedures to identify muscular activity in terms of muscle innervation and potential training effects. Our approach points out future development steps of similar VR exergaming systems, assisting developers to optimize their efforts in promoting physical activity.
The Icaros flight session appears to provide little to no cardiovascular benefit. Based on WHO guidelines for resistance training, muscle activity during the sessions occasionally met the lower threshold for effective muscle activation. The lower back’s muscle activation corresponds to plank variations with instability devices (eg, planks on exercise balls) [
By contrast, Icaros can provide improved muscle strength, especially for the dorsal muscle chain. Differentiated muscle activation can be achieved in virtualized worlds by, say, requiring the user to spend more time in a pitch down position, thereby shifting the body’s center of gravity on the pitch axis. But achieving the 30 minutes of daily cardiovascular activity recommended by the WHO requires dynamic instead of isometric movements.
Performing a plank position without external control of one’s body posture can result in hyperlordosis, an excessive extension of the lumbar region. Added stress on the visual and vestibular systems is associated with higher immersiveness but can lead to proprioceptive signals receiving less attention by the user. Spending time in flexed and awkward positions has been associated with low back pain syndrome [
Motivating the public to engage in physical activity is probably one of the most important and difficult tasks of the health sector. Gamification of physical exercise can help not only to motivate physical activity but also to promote social contact and interaction.
Future full-body and fully immersive concepts should focus on increasing dynamic muscle activation while considering user susceptibility to cybersickness and motion sickness. VR systems can give the public a refreshing and enjoyable form of physical activity.
In prevention and therapy, movement quality is a fundamental component of effective resistance training to benefit health. It is crucial, therefore, that future VR-based training systems follow the recommendations of sport and exercise science.
maximum voluntary isometric contraction
NASA Task Load Index
Physical Activity Enjoyment Scale
rate of perceived exertion
surface electromyography
Simulator Sickness Questionnaire
virtual reality
World Health Organization
This research was supported by the Institute of Movement Therapy and Movement-oriented Prevention and Rehabilitation of the German Sport University. We would like to thank the Icaros company for providing us with the necessary hardware and software. No financial agreements of any kind were conducted between the company and the researchers.
None declared.