The optical acceleration cancelation (OAC) strategy, based on Chapman’s (1968) analysis of the outfielder problem, has been the dominant account for the control of running to intercept fly balls approaching head on. According to the OAC strategy, outfielders will arrive at the interception location just in time to catch the ball when they keep optical acceleration zero. However, the affordance aspect of this task, that is, whether or not an approaching fly ball is catchable, is not part of this account. The present contribution examines whether the scope of the OAC strategy can be extended to also include the affordance aspect of running to catch a fly ball. This is done by considering a fielder’s action boundaries (i.e., maximum running velocity and –acceleration) in the context of the OAC strategy. From this, only when running velocity is maximal and optical acceleration is non-zero, a fielder would use OAC to perceive a fly ball as uncatchable. The present contribution puts this hypothesis to the test. Participants were required to try to intercept fly balls projected along their sagittal plane. Some fly balls were catchable whereas others were not. Participants were required to catch as many fly balls as possible and to call ‘no’ when they perceived a fly ball to be uncatchable. Participants’ running velocity and –acceleration at the moment of calling ‘no’ were examined. Results showed that participants’ running velocity was submaximal before or while calling ‘no’. Also running acceleration was often submaximal. These results cannot be explained by the use of OAC in judging catchability and ultimately call for a new strategy of locomotor control in running to catch a fly ball.

In this paper, we assess the use of Inertial Measurement Units (IMU) in recognising different volleyball-specific actions. Analysis of the results suggests that all sensors in the IMU (i.e. magnetometer, accelerometer, barometer and gyroscope) contribute unique information in the classification of volleyball-specific actions. We demonstrate that while the accelerometer feature set provides the best Unweighted Average Recall (UAR) overall, "decision fusion" of the accelerometer with the magnetometer improves UAR slightly from 85.86% to 86.9%. Interestingly, it is also demonstrated that the non-dominant hand provides better UAR than the dominant hand. These results are even more marked with "decision fusion". CCS CONCEPTS • Human-centered computing → Interactive systems and tools; • Interaction paradigms → Web-based interaction.

With this monograph we introduce a new, systematic taxonomy of Sports Interaction Technology (Sports ITech) that defines a design space of existing and future work in this domain. We set the taxonomy in a context of our view on sport science and sports practice, target outcomes of sports and the underlying factors influencing them, and the role that sports technology plays to support sports science and practice. In that setting we systematically build and illustrate a taxonomy for the design space for Sports ITech as a sub-area of sports technologies, with specific attention for the adequate inclusion of knowledge from the sports

CHIPLAY sees many works on Sports Interaction Technology [17], movement-based games [7], exergames [5], and other work inspired by elements of sports. Similarly, many CHIPLAY works concern gamification, defined as "using design elements characteristic for games in non-game context" [4, p9], to make non-game activities more interesting (168 search results up to 2022, many on user type modelling [20]). Given the ease and success with which gamification practice has been applied [8], we discuss here a parallel in the use of sports-elements in a non-sport context, translating an existing definition of Sportification from the field of sports organisation into HCI and showing that Sportification is its own design strategy suitable for our playful HCI field.Heere [9, p4] introduced Sportification from a sports management perspective, in two ways. One, "view, organize or regulate a non-sport activity in such a way that it resembles a sport and allows a fair, pleasurable, and safe environment for individuals to compete and cooperate and compare their performances to each other and future and past performances". Two, "(to) add a sport component to an existing activity in order to make it more attractive to its audiences".However, this does not yet sufficiently explain which specific elements make for the Sportification of non-sport activities. Furthermore, although Heere mention examples outside sports: 'the Eurovision song festival', 'The Voice', and 'You've got Talent', their work focuses more on the first part of the definition, non-sport contexts that are made into sport (e.g., play becomes sports with skateboarding [1] or games become sports with esports).