The effects of positive and negative verbal feedback on repeated force production

Studies indicate that providing subjects with positiveaugmented feedback (PAF) enhances motor learning and performance compared to negative- (NAF), or no-feedback. However, in the majority of these studies, the performance feedback was provided relative to a peer-group (e.g., "your performance is higher/lower than the norm"). Here we examined how different, and less explored types of PF and NF, influenced repeated force production of 22 resistance-trained subjects (50%-males). On three occasions, subjects completed 12 isometric maximal voluntary contractions (MVC) with their elbow flexors, while electromyography (EMG) was collected from their biceps and triceps brachii muscles. After every second repetition, subjects received either PF (e.g., "You are looking great."), NF (e.g., "You are not trying."), or no-feedback. All measurements were normalized to pre-test MVCs and reported aspercentages. Subjects applied greater forces in the NF condition compared to the PF (4.3%, 95%CI: 2.8, 5.8) and no-feedback (7.9%, 95%CI: 6.4, 9.4) conditions. Similarly, subjects demonstrated greater biceps EMG activity in the NF compared to the PF (6.6%, 95%CI: 3.7, 9.4) and no-feedback (2.8%, 95%CI: 9.9, 15.6) conditions. We speculate that NF can lead subjects to exert greater forces bysignaling that their efforts are lacking. These results indicate that under some circumstances, NF can have practical benefits over no-feedback and even PF; however, we note that NF should be delivered with caution since it may also hinder motivation and self-efficacy over time.