Interval Training with Astrojumper

Andrea Nickel* UNC Charlotte

Hugh Kinsey* UNC Charlotte

Heidi Haack* UNC Charlotte

Mykel Pendergrass* UNC Charlotte

Tiffany Barnes†

UNC Charlotte

ABSTRACT

The prevalence of obesity among adolescents and adults in the U.S. is a matter of concern. Exercise video games reach a wide audience and can be used to motivate increased physical activity. We have previously developed Astrojumper, an exergame exploring game mechanics that provide a fun experience and effective exercise, and have now developed a new version of Astrojumper that supports interval training through additional mechanics. We believe the new version will improve upon the first in player motivation, enjoyment and replayability, and also in the level of physical challenge the game affords its players.

KEYWORDS: virtual reality, exercise games, interval training

INDEX TERMS: K.4.0 [Personal Computing]: General—Games

1 INTRODUCTION

One-third of children and adolescents (age 2-19) are overweight or obese [8], and over two-thirds of U.S. adults (age 20 and older) are overweight or obese [6]. About one-third of high school students report engaging in physical activity on 5 or more days of the week, but as adolescents get older, participation in regular physical activity greatly decreases [3]. Many Americans do not reach the minimum exercise recommendations for health benefits, but the adoption of regular physical activity habits can alleviate a number of health problems in addition to obesity: cardiovascular disease, hypertension, diabetes and several psychological disorders, including depression, can be prevented or lessened [11]. Video games reach a wide audience: in 2009, 67% of households played video games [4]. Video game playing has traditionally been a sedentary activity, but the popularity of using video games for exercise has increased thanks to the commercial availability of motion sensing devices, such as the Nintendo Wii remote and Wii Fit balance board, and the 2010 Microsoft Kinect. These devices have made it possible to design games that use players' physical movements as game mechanics. Exercise games, or exergames, can address a wide range of health issues [9, 10] and in addition to the physical challenge can present an engaging, motivating play experience often preferred over traditional or less engaging, repetitive exercise [1]. This means that video games have great potential as an attractive way to increase daily physical activity. The present work aims to build upon our previous exergame research, and explore the balance between physical challenge and fun gameplay, attempting to maximize both. The Astrojumper virtual reality exercise game was developed both to engage children with autism in physical activity and as an

exploration of fun and effective exergame mechanics, and was shown to provide effective exercise, increased heart rate, and an enjoyable experience [5]. We have developed a new version of the Astrojumper game that supports interval training through additional game mechanics. Interval training intersperses repeated periods of high-intensity exercise with periods of low-intensity exercise or rest (recovery periods). Performing more work at a higher intensity can improve both aerobic and anaerobic fitness in a shorter amount of time than continuous training [7]. Interval training is effective for enhancing sports performance [2], but is also applicable for exercisers who want to increase their fitness level and the efficiency of their exercise sessions, or introduce change in a workout routine to prevent boredom. We believe that the interval training version of Astrojumper will improve upon the previous game in multiple areas, including level of player exertion, and enjoyment and replayability due to the greater variety in gameplay.

2 PREVIOUS WORK ON ASTROJUMPER

Astrojumper was first developed for the Cave Automatic Virtual Environment platform, and used electromagnetic trackers worn by the player to detect the player's position and movements. The game is set in a space environment, and players dodge around planets that are flying toward them. A player's score continues to increase as they successfully avoid planets, but will decrease if they collide with the planets. Players may also try to hit bonus gold planets to gain extra points. Occasionally throughout the game a UFO will appear and attack the player by firing lasers at them; these lasers must be dodged and the player may fire lasers back at the UFO by making punching motions. The results of a 30-person user study showed the game was considered enjoyable and was effective in raising player heart rates and providing exercise [5]. Since then, the game has been reworked to support use of the Microsoft Kinect instead of the CAVE, which frees the player from the physical connection that was previously required for use of the tracker system. The Kinect version of Astrojumper is mostly identical to the CAVE version, but changes the first-person view to a third-person view by making the player's Kinect skeleton visible, and adjusts several game difficulty settings due to the increased tracking sensitivity of the Kinect.

3 INTERVAL TRAINING IN ASTROJUMPER

The interval training version of Astrojumper includes additional game mechanics in the form of minigames. Minigames are used for the high-intensity exercise intervals, and are alternated with low-intensity periods during which the player dodges planets as in the original game. A 15-minute game session includes a 3-minute warm-up, during which the player dodges initially slow planets that gradually increase their speed, followed by a series of minigames (high-exertion intervals that last for 30 seconds, 45s, 60s, 60s, 45s, and 30s respectively) interspersed with 60-second low-exertion periods where the player simply dodges planets, and finally a 2.5-minute cool-down time where the player dodges planets with speeds that gradually decrease. Three different minigames have been added to Astrojumper, and are described in the following sections. Each minigame focuses on

*e-mail: {anickel1, hkinsey1, hhaack, mpender5}@uncc.edu †e-mail: tiffany.barnes@gmail.com

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a different form of exercise (upper body, lower body, cardio) and, while they are designed to require more exertion than the planet-dodging mechanic, can still dynamically adjust their difficulty level by continuously monitoring a player's performance and adjusting factors such as the numbers and speed of game objects to provide the player with a challenge that is achievable.

3.1 Interval Training Minigames

Figure 1. Space Invaders [1], Asteroid Belt [2], Space Rock Band [3].

3.1.1 Space Invaders

The Space Invaders minigame focuses on upper body exercise. The player is confronted by several waves of forward-moving UFOs, and must constantly fire lasers at them by punching rapidly. Each UFO must be hit a certain number of times before it is destroyed, and in order for the player to gain points. If the player fails to destroy all the UFOs before they get too close, the player receives a point deduction. The rapid punching movements over a period of 30-60 seconds provide a period of higher intensity exertion. Difficulty can be adjusted by changing the number of UFOs advancing toward the player, or the speed or health of the UFOs the player must destroy.

3.1.2 Asteroid Belt

The Asteroid Belt minigame targets the player's lower body area by presenting obstacles that can only be avoided through movements that utilize the lower body. The Asteroid Belt minigame launches a number of asteroids at the player in a horizontal line. The asteroids are placed so that the player will either have to duck under a high row of asteroids, or jump over a low row of asteroids in order to avoid colliding with them and losing points. The asteroid positioning (high or low) is randomly determined during the game so the player will encounter a different pattern each time. The player must successfully jump over and duck under the asteroids for a 30-60 second time period. The difficulty can be adjusted by increasing the speed at which the asteroids advance toward the player.

3.1.3 Space Rock Band

Inspired by the Rock Band mechanic that gives players a series of glowing notes that must all be played correctly to succeed, the Space Rock Band minigame is designed to give the player a more intense version of the physical challenge they encounter while dodging planets. In this minigame, waves of stars come toward the player in different locations, and the player 's goal is to hit all of the stars in succession to play difference sound effects and earn bonus points. The stars are positioned in order to get the player to move around the entire play space: this consists of the player moving from one side to another, or reaching from the top to the

bottom of the screen to hit as many stars as they can. Touching stars gives the player points, and additional points can be earned for hitting all of the stars that appear in a 30-60 second minigame. Space Rock Band's difficulty can be adjusted using the numbers and configurations of stars, and how quickly they move toward the player.

4 CONCLUSIONS AND FUTURE WORK

In an upcoming study, we will compare the original Kinect version of Astrojumper with the new interval training version of the game. We believe that the additional mechanics and varying structure of the interval training game will improve upon the original game in both player enjoyment and replayability, and the amount of physical challenge presented. We will collect data on study participants' video game-playing habits, activity level and exercise motivations, and measure increases in heart rate and energy expenditure for players for both game versions to be able to compare the exercise effectiveness of both games. We will also ask players for their perceived exertion rating of each game using a 1 (no exertion) to 5 (very hard exertion) scale, and also their ratings on 7-point Likert scales of game challenge, motivation, and enjoyment. We hope that this work will offer some more insight into a combination of game elements that results in both an enjoyable and physically challenging game experience, and into the potential that exergames have to become really effective tools for exercise.

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