The purpose of this study was to investigate cardiorespiratory responses to pseudorandom binary sequence exercise. Since control of heart rate (HR) in response to light exercise is mainly based on parasympathetic withdrawal, and sympathetic activity begins to increase when HR approaches 100 beats/min (bpm) level, we hypo thesized that HR dynamics in man might be different, especially on frequency domain analysis in response to pseudorandom binary sequence (PRBS) exercise above and below 100 bpm HR level. PRBS tests were the combination of two PRBS patterns and three work rate levels adjusted to the HR level above, around, and below 100 bpm. PRBS 1 had 15 units, each of 10-s duration for a total of 150 s, and PRBS 2 had 31 units, 5-s duratin for a total of 155 s.
　During PRBS exercise below 100 bpm, the gain of HR dynamics was higher and the phase shift was smaller than those above 100 bpm. The different HR dynamics between above and below 100 bpm might be reflected by different control of parasympathetic withdrawal and sympathetic activity. It was suggested that the combination of work rate level, duration of each work, and unit numbers of work were essential to pseudorandom binary sequence exercise.

DESCENTE SPORTS SCIENCE Vol.16/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE