| Object avoidance strategies are dictated by the layout of the environment, placement of obstacles in the travel path, and the perception of time-to-contact. The ability to accurately determine timing and recognize the time before a collision is known as time-to-contact (TTC) (Lee, 1974). Little research has examined obstacle avoidance at varying speeds and with the inclusion of an end-task. The purpose of this study was to examine the effects of sport-specific training, locomotion speed, and an end-task on circumvention and TTC around a single obstacle. Participants (varsity soccer players, n=10 and gender matched non-athletes, n=9) travelled along a 13m pathway towards a goal marked on the floor and avoided a single obstacle placed in one of five obstacle locations: middle, 20cm left of middle (left), 20cm right of middle (right), 50cm in front of middle (backward), and 50cm behind middle (forward). Participants completed four trials per obstacle location while completing four conditions: 1) walk, 2) run; 3) walking with a passing end-task (walk+); and 4) running with a passing end-task (run+). During the end-task conditions, a soccer ball was placed on the goal and was to be kicked at the wall with the inside of either foot.;Results revealed that soccer players and non-athletes appear to avoid obstacles similarly with respect to the side of avoidance. However, differences between the two groups became more apparent with greater task difficulty and when regarding the aspects that contributed to their circumvention decisions. Both groups avoided the obstacle toward the side that afforded more space when the obstacle was placed in the left and right positions, and circumvented the obstacles to a similar side (left or right) when the obstacle was placed in all other locations. Soccer players were observed to circumvent the obstacle to the opposite side of their foot preference during the walk+ and run+ conditions, but only for the middle (walk +, r(58)=-0.27, p=0.04; and run+, r(58)=-0.30, p=0.02) and forward (run+, r(58)=-0.27, p=0.04) obstacle locations. Soccer players were also more likely to avoid to the opposite side of their pass foot when the soccer ball was involved (walk+, r(298)=-0.41, p <0.001; run+, r(298)=-0.41, p<0.001), for all obstacle locations. Soccer players also produced a consistent clearance time with regards to TTC, such that no differences were found between conditions or obstacle locations (p>0.05). For non-athletes, no significant relationships were found between foot preference of the presence of the ball and circumvention direction. However, when examining TTC, non-athletes did not produce a consistent TTC on the run+ condition. For this condition, non-athletes began their deviation earlier for the forward location than the middle location (F(2,16)=4.10, p=0.04).;It appears that the difference in soccer players' and non-soccer player's direction of circumvention was greatest with the inclusion of an end-task and the speed increase. When soccer players walked (i.e., different from training speed), environmental cues dictated the direction of avoidance rather than the end-task. When performing the end task at faster, more familiar speeds, soccer players used end-state body orientation for kicking to dictate the direction of avoidance. Conversely, non-athletes' direction of circumvention was not affected by footedness or passing foot. It appears that their actions were largely dictated by the obstacle location and perception of time prior to contact with the obstacle. Evidently, an increase in task difficulty (inclusion of speed and end-task) resulted in differences between soccer players and non-athletes. Similarly, the position of the obstacle has a large impact on how both participant groups approach and avoid the obstacle. |
