Effects of psychological and physiological challenges on heart rate, T-wave amplitude, and pulse-transit time.

The reactive sensitivities of T-wave amplitude (TWA), pulse-transit time (PTT) and heart rate (HR) were examined in response to psychological, physiological, and combined challenges. In one experiment, 20 subjects performed 1-min arithmetic and combined arithmetic-with-cycling tasks, with HR and TWA being measured. The former showed significant reactive sensitivity, but TWA attenuation reached significance only in the combined challenge situation. In another experiment, 18 males performed 1 min arithmetic tasks, before, during, and following sustained low and moderate intensity cycling. Pulse-transit time was also gauged in this second study. The results showed that HR increased reliably to all challenges, TWA attenuated in response to the arithmetic task both at rest and during exercise, but displayed the paradoxical augmentation to sustained exercise, and PTT decreased significantly to exercise, but it did not decrease reliably to the arithmetic task in any of the conditions. These results suggest that the time course (tonic versus phasic) of the challenge, rather than its psychological or physiological nature, may be the determinant factor in TWA reversal.