CORRELATION INTEGRAL OF BLOOD-PRESSURE AS A MARKER FOR EXERCISE INTENSITIES

The Purpose of this study was to test the hypothesis that the correlat ion integral technique detects altered regulation of cardiovascular fu nction during graded treadmill exercise. Arterial blood pressure (BP) was measured via telemetry before and during graded treadmill exercise in Sprague-Dawley rats. During treadmill running at mild, moderate, a nd heavy exercise intensities, the slope of the correlation integrals (SCT) continuously increased from 5.45 +/- 0.17 to 7.12 +/- 0.18, 7.92 +/- 0.23, and 8.40 +/- 0.23, respectively. However, corresponding cha nges in pulse interval, blood pressure, and systolic blood pressure wi th increasing workload were not consistently observed. Low-frequency, midfrequency, and high-frequency powers of BP were not different betwe en adjacent exercise grades; only the low-frequency component of pulse interval was different between resting state add mild exercise, and B P variance was significantly different between mild and moderate grade s. Comparison of the SCI values with those obtained from surrogate dat a sets suggests that these differences originate mainly from nonlinear components in the cardiovascular control system. These findings suppo rt the hypothesis that SCI detects alterations in cardiovascular regul ation associated with graded exercise. Furthermore, SCI may be superio r to linear techniques in detecting altered regulation with changing e xercise intensities.