Mental challenge elicits "additional" increases in heart rate during low and moderate intensity cycling.

The combined effects of exercise and mental challenge on heart rate (HR) and T-wave amplitude (TWA) were studied. Twenty male students cycled at low (40% of their relative maximal HR reserve (MHRR), for 15 min) and medium (60% MHRR, for 10 min) intensity exercise workloads. Subjects performed a series of mental arithmetic problems for one minute each time: two min before cycling, 10 min into low intensity cycling, 10 min into medium intensity cycling, and two and 20 min, respectively, after cycling. During both exercise workloads, the mental arithmetic elicited significant additional increases in HR. Although TWA decreased in response to mental arithmetic at rest, no changes in TWA were observed in response to mental task during exercise. However, TWA increased significantly following the mental challenge. These results suggest that even a mild mental challenge is capable of inducing further changes in the autonomic response during low and moderate exercise.