Locomotor pointing is a task that has been the focus of research in the context of sport (e.g. long jumping and cricket) as well as normal walking. Collectively, these studies have produced a broad understanding of locomotor pointing, but generalizability has been limited to laboratory type tasks and/or tasks with high spatial demands. The current study aimed to generalize previous findings in locomotor pointing to the common daily task of approaching and stepping on to a curb. Sixteen people completed 33 repetitions of a task that required them to walk up to and step onto a curb. Information about their foot placement was collected using a combination of measures derived from a pressure-sensitive walkway and video data. Variables related to perceptual-motor regulation were analyzed on an inter-trial, intra-step and inter-step level. Similar to previous studies, analysis of the foot placements showed that, variability in foot placement decreased as the participants drew closer to the curb. Regulation seemed to be initiated earlier in this study compared to previous studies, as shown by a decreasing variability in foot placement as early as eight steps before reaching the curb. Furthermore, it was shown that when walking up to the curb, most people regulated their walk in a way so as to achieve minimal variability in the foot placement on top of the curb, rather than a placement in front of the curb. Combined, these results showed a strong perceptual-motor coupling in the task of approaching and stepping up a curb, rendering this task a suitable test for perceptual-motor regulation in walking.
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.
Best practice in skill acquisition has been informed by motor control theories. The main aim of this study is to screen existing literature on a relatively novel theory, Optimal Feedback Control Theory (OFCT), and to assess how OFCT concepts can be applied in sports and motor learning research. Based on 51 included studies with on average a high methodological quality, we found that different types of training seem to appeal to different control processes within OFCT. The minimum intervention principle (founded in OFCT) was used in many of the reviewed studies, and further investigation might lead to further improvements in sport skill acquisition. However, considering the homogenous nature of the tasks included in the reviewed studies, these ideas and their generalizability should be tested in future studies.
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