Low cost interactive bicycle system Renato Silveira Instituto de Informática UFRGS Porto Alegre, RS rsilveira@inf.ufrgs.br Daniela G. Trevisan Instituto de Informática UFRGS Porto Alegre, RS dtrevisan@inf.ufrgs.br Luciana Porcher Nedel Instituto de Informática UFRGS Porto Alegre, RS nedel@inf.ufrgs.br ABSTRACT This paper provides a low cost implementation of an indoor ergonomic bicycle system allowing the user to navigate in a virtual city. The low cost approach is guaranteed by us- ing the ARToolkit library as an alternative way to capture the bicycle speed and the use of mouse buttons to control movement direction in the virtual world. Besides we intend to study the user reaction in relation to different stimuli while the user is exercising. The first scenario is based on a passive video clip stimulus and the second one is based on an interactive virtual stimulus. As a result, usability tests are performed with the goal to identify practical basis that explains how virtual reality interfaces might provide moti- vation for interactive fitness applications. Keywords Virtual bicycle, usability, human-computer interaction, fit- ness. 1. INTRODUCTION Human-computer interaction (HCI) research usually fo- cuses on the design, implementation and evaluation of in- teractive systems in the context of a user’s task and work [6]. One of the issues to be addressed in this field is to un- derstand the people behavior while using interfaces, trying to identify human beings perceptive, functional and cogni- tive resources, and how these resources are available during the accomplishment of a human-computer based task. Once these resources are identified and their activity quantified, designers of computational interfaces will be able to consider these limitations in the design of new HCI systems including virtual and mixed interfaces. One of the most challenging aspects on the new interac- tive systems development lies on the ability to use computer- based information into the real world tasks. This kind of sys- tems, can become an extremely effective operating medium, once it is based on monitoring the state of the user and/or the environment in real time, and adapting or augmenting Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SVR ’2007 Petropolis, Rio de Janeiro, Brasil Copyright 200X ACM X-XXXXX-XX-X/XX/XX ...$5.00. the computational interface to significantly improve the user performance on the task execution [8] [5]. The majority of aerobic exercises consists of multiple rep- etitions of movements in a long period of time. Sometimes, the lack of sensorial stimulus on a activity like this, added to the fact of being held indoors, may lead the user to fell un- motivated. In this way, the use of virtual reality, computer graphics and interaction techniques can add significantly to this issue. In this work we propose a low cost implementation of an indoor ergonomic bicycle system allowing the user to inter- act in a virtual city. The low cost approach is guaranteed by using the ARToolkit library [7] as an alternative way to cap- ture the user speed and then navigate in the virtual world. With this system we intend to study the user reaction in re- lation to two kinds of stimulus while the user is exercising. The first scenario is based on a passive video clip stimulus and the second one is based on an interactive virtual stimu- lus. As a result, series of usability tests are performed with the goal to identify practical basis that explains how virtual reality interfaces might provide motivation for interactive fitness applications. The paper is organized as follows. Section 2 presents some related works in interactive virtual reality systems focusing on the fitness activity. Then, in Section 3 we presented the testbed application providing details about the system design allowing the user to reproduce it. In Section 4 we present all the aspects needed to proceed with the system usability evaluation and in Section 5 we describe our exper- iment preparation. In Section 6 we present our results and the discussion and in Section 7 we make some final com- ments about the work developed and our on-going research. 2. RELATED WORKS In previous work, May [9] presented an interactive art- work. This system entitled Legible City consisted of models of three cities: Amsterdam, Manhattan and Karlsruhe. The buildings are fabricated from textual narratives taken from material relating to the locale, which the viewer can read as they explore. Navigation is achieved by “riding” a modi- fied exercise bicycle mounted in front of a large screen onto which the computer generated image is projected. In the aerobics domain, Davis and Bobick [4] presented a prototype system for a virtual Personal Aerobics Trainer. In this system, users can select which aerobic moves, which songs, and which instructor they want for their workout ses- sion. The system guides the user through the workout while watching and commenting on the user’s performance.