How to benefit from augmented feedback? The influence of motivational and informational content of augmented feedback and the influence of task complexity.

Augmented feedback (aF) positively influences motor performance by enhancing motivation and/or by providing information about task execution. It was speculated that aF-induced performance increments that rely on motivation should also occur when providing incorrect aF, while performance increments that rely on guidance towards "successful executions" (i.e. improved performances) should only occur when aF is correct. We further hypothesised that the informational content of aF is more important in more complex motor tasks. Thus, 32 participants received two forms of aF (correct, incorrect) during maximal voluntary contractions (MVC's; maximise force without time constraints; less complex) and maximal explosive contractions (MEC's; maximise force in the shortest possible way; more complex) of the knee extensors. Peak torque (MVC), peak rate of torque development (MEC) and EMG signals of rectus femoris (RF) and vastus lateralis were recorded. Correct and incorrect aF significantly enhanced MVC performance, indicating that performance improvements resulted mainly from the motivational property of aF. The observed trend towards increased RF muscle activity supports this conclusion. In contrast, while correct aF positively impacted MEC performance, incorrect aF had a negative influence. This indicates that the informational property of aF guided participants towards movement executions resulting in improved (correct aF) or decreased (incorrect aF) performances. The observed simultaneous decrease in muscle activity suggests that participants changed motor strategy, supporting the guiding role of aF. Our results demonstrate that the motivational aspect of aF dominates in maximal tasks with lower complexity (MVC), while the informational aspect is used during more complex maximal tasks (MEC).