| Arousal is a component of several emotional responses and is characterized by feelings of apprehension, nervousness, and tension. The physiological manifestations of arousal include increased heart rate, blood pressure, sweating, and musculoskeletal disturbances, such as restlessness, tremors, and feelings of weakness. The neuroendocrine substrates responsible for these physiological changes can potentially modulate the functions of spinal circuits underlying motor performance. We hypothesized that neuromodulators activated during the arousal response would result in impaired motor performance. Three experiments were performed to test this hypothesis. The purpose of the first experiment was to determine the effect of arousal in men and women on the moment-to-moment performance of a motor task. While both stressors increased arousal, only a noxious stressor (electric shock) and not a cognitive stressor (mental arithmetic) impaired the steadiness of a pinch task. Although women exhibited more of an impairment than men, the reduction in steadiness was largely unrelated to the magnitude of the arousal response. The purpose of the second study was to determine the effect of trait anxiety and stressor intensity on arousal and motor performance during the same pinch task. We found that cognitive and physiological arousal increased with shock stressor intensity and was associated with decreased performance of the pinch grip. In addition, electric shock reduced steadiness irrespective of the level of trait anxiety but that only those subjects with high levels of trait anxiety experienced a change in steadiness with variations in stressor intensity. The third experiment determined the effect to two stressors, task complexity and electric shock, on cognitive arousal, steadiness of a pinch grip, and the maximum force that could be exerted during a pinch grip. When the shock stressor was compared with a physical challenge stressor (bilateral grip tasks), steadiness of submaximal pinching and peak forces during maximal contractions were reduced for the shock stressor, but not for bilateral contractions. Taken together, the findings from these studies suggest that activation of the arousal response is associated with impaired motor performance. |
